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Dominik Biner Power supply and motion system for

1. M NALAIS Hes so wanie cp Tokyo February 20 2008 o SPRAY Chuo University 3 Analyses and first approaches 3 1 Introduction to this paragraph Because many things are unknown or not defined yet only possible approaches are described in this paragraph More detailed realisation suggestions for the different parts will be treated in chapter 4 This section is also used for the first description of the approaches to my person in charge in Japan Dr Eng Yasuharu Kunii and serves as help for the following realisation 3 2 Optimisation of the wheel s shape First of all read the study results about the wheel form done by Kojiro lizuka Yoshinori Sato Yoji Kuroda and Takashi Kubota see appendix 1 concluded that the effects of hardening soil and shearing stress low slip ratio are the most important So the aim is to combine these two effects as good as possible How it can be seen in figure 11 of appendix 1a and table 2 of appendix 1b the elastic wheel as well as the pentagon and the combined wheel types provoke a hardening of the soil But the slip ratio for the pentagon typed wheel is relatively high see fig 12 appendix 1b In contrast the combined types pentagon circular wheel with lugs and the elastic wheel combine the two effects fairly well But the elastic wheel tends to be deformed by the charge and thus this type can not be used In my opinion the combined wheels see fig 6 ap
2. 7 7 NALAIS i Hes so waius cp Tokyo February 20 2008 o SPRAY Chuo University For the cell voltage measure required for detecting the start of charge and determinate the charge level of the batteries either an analogue input of the processor is used or an accordant logical signal is generated Instead of analogue inputs external A D converters can be deployed The detection of critical values of cell voltage battery current or battery temperature can be realised by analogue circuits which directly act by themselves without the use of the microprocessor For example when the discharge current exceeds a certain value the batteries are directly disconnected from the load by the analogue circuits 3 3 4 Approach for the generation of the different voltage levels To generate the different voltage levels 5V 12V and 24V from the battery voltage standard voltage regulators could be used They cause many losses and therefore it s better to use DC DC converters but in the first instance my person in charge Professor Kunii doesn t want to use them So this point has to be discussed further see chapter 4 3 To choose the power class of each regulator we need to know the consumption for each level Depending of the power consumption of each level it has to be determined whether it s better to use the battery voltage or the output of the 24V regulator as input voltage for the 12V regulator see pictures below
3. M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University Comparators are also necessary for the realisation of the uP independent security measures described in the previous chapter For realising this circuit the same components as for the cell voltage measuring circuit are deployed The LM324 as operational amplifier op amp the MAX197B as A D converter and the LM339 as comparator Again the reference voltage is given with a 1MQ potentiometer As mentioned in chapter 4 4 4 the converter MAX197 has eight analogue inputs and therefore only one integrated circuit is required for transmitting the current value of each battery unit to the microprocessor In order to be able to measure negative and positive currents charge and discharge current the op amp has to be supplied with 5Vdc to allow the amplification of a negative voltage over the shunt resistance as well Therefore an additional voltage regulator is necessary for generating the negative supply voltage The comparator also has to be supplied with 5Vdc The SMD components LMV324 and LMV339 can not be used with this power supply range The maximum allowed difference between the positive and the negative supply voltage is 5 5V see datasheets appendices 5f and 5g Unfortunately in the datasheets it s not clearly defined if they can be used with a dual supply voltage and there is no information about the LMV324 s behaviour with a negative output
4. o Power supply and motion system for planetary rover M NALAIS Hes so wanie cp Tokyo February 20 2008 o SPRAY Chuo University Hence User is set to 2 2V and we get the following current measuring range U uiii 0 5V tice 4 5V U ep u en Tem u Ug U ag 2 gt I BR N EN gt U 2 a I I 2 Er m om 11 04A 2s Oe As shown in figure 32 the relation between the delivered output voltage and the measured current is linear and thus there is a constant ki in Wa slope of the straight line With a nominal current of 3A the total range is 19 2A 9 6A and we get the following constant U u min 0 5V U put max 4 5V gt AU 4V AI I I 19 2A P max positive P max negative AI gt k 208 33 AU 208 33 I Therewith the formula for the relation between the output voltage and the measured current can be written as follows U oy U seg k out Remark For more detailed information about the current sensor see the datasheet on the enclosed CD appendix 5n As shown in chapter 3 4 the current delivered by the battery for supplying the motors is rectangular because the current flows into the battery during the low time of the PWM signal Thus the output voltage delivered by the current sensor is also rectangular and has to be filtered in order to get the average value necessary for estimating the battery s capacity by the uP This is done
5. with Z as gate current G Qs Qos Qep as the total charge at the gate t is the on off time t Or tae Remark The total gate charge Qg depends of the drain source voltage thus of the supply voltage of the H bridge which in our case correspond to the battery voltage Moreover the drive resistance in series to the gate has also influence on the switching operation because together with the input capacity Cis of the MOSFET it represents an RC element The time constant t of this RC element determines how fast the control voltage Ucs reaches its final value Ugs has a direct influence on the resistance between drain and source Ros on For switching the transistor on the input capacity Cis has to be charged and discharged when switching off In fact while switching the MOSFET on the capacity Ces is charged by a positive gate current flows into the gate and the capacity Cep which at this moment is charged at the supply voltage of the H bridge has to be discharged with a current of the same polarity While switching off this process is inverted and consequently a negative gate current is necessary t switch on U esi z U G5 pa fize T Roue Cisse Cis Cos Cop uft Umax switch on T 2T 37 Ar 57 switch off T 27 37 Ar 57 switch off U ss t U os pai ses gt T R Gate i Cis gt Cis Ces Con Remark The calculation with the exponential charge or discharge is only rudimental true becaus
6. 2 5V P nom U U I gt I out max ref Pnom 0 625 With Ipnom 3A the current range is 9 6A and with a nominal current of 6A the maximal current range of 19 2A is reached With the LTSR types the reference voltage of 2 5V which corresponds to the zero current can be given externally 1 9V lt Uret lt 2 7V and therefore adapt the current range As the charge current is smaller Icharge max 7 7A than the discharge current Igischarge max 10A the reference voltage Ure is adapted In that case the formulas for calculating the available current range are the following i U U iin P nom P max negative u 0 625 I as U max Uy l P nom P max positive 0 625 The aim is to use as much as possible of the available output voltage range in order to reach the highest possible accuracy for the subsequent A D conversion This means that the limits of the current range lPmax_negative aNd lPmax positive are chosen as near as possible from the maximal current values to measure On this account Ipnom is set to 3A The sensor is installed so that the charge current corresponds to a negative current Thus Uret is reduced in order to get a bigger positive than negative current measuring range The maximal discharge current is 7 7A and so Ure has to be at least U pann 0 5V I 3A U U p i I I A of u P nom 7 7A max negative 0 625 gt Upp 0 25 U nin 2 104V P nom Biner Dominik Diploma thesis page 48 78
7. Biner Dominik Diploma thesis page 40 78 ooo Power supply and motion system for planetary rover NALAIS Hes so wais C tp m x ea Tokyo February 20 2008 Chuo University mentioned in chapter 4 4 2 the conversion of the analogue signals is done by means of the A D converter MAX197B which generates a 12Bit digital signal It can be single supplied with 5Vdc is available with SMD package and has 8 analogue input channels and thus the multiplexer already integrated Therefore it needs only one integrated circuit to measure each cell voltage of one battery unit The datasheet of the MAX197 is on the enclosed CD appendix 5m By using A D converters all the necessary detections concerning the cell voltage described in this paragraph chapter 4 4 can be taken over by the microprocessor Only the double securities have to be taken over by analogue circuits if the consequential actions have to be independent of the microprocessor Due to the missing time the programming of the microprocessor SH 2 for controlling the converter isn t done during this diploma work Therefore to facilitate the work of the next student that will take care of this in the following chapter the A D converter MAX197B is described and it s defined how to use it in this application 4 4 4 1 How to use the converter MAX197 description of the device The MAX197 employs a standard microprocessor interface The three state dig
8. Such as for the cell voltage control a uP independent security can be installed This means that as soon as the discharge current reaches 10A per battery unit the analogue control circuit disconnect the batteries from the load by itself without the need of an order from the microprocessor The principle is exactly the same as for the double security against a too low cell voltage described in chapter 4 4 3 1 In order that both measuring circuits cell voltage and battery current can actuate the bipolar transistor the circuit shown in figure 18 has to be adapted as follows 2aVde signal from p up microprocessor 2 U39A signals from _ 3 an analogue circuits 7400 Fig 38 Driving circuit for the relays used for switching between the charge and the discharge of the batteries switching through analogue circuits possible uP independent faulty But the problem is that the signal provided by the comparator of the battery current measuring circuit will go back high as soon as the batteries are disconnected from the load current falls down to OA Thus the batteries are directly reconnected to the load To solve this problem a RS latch is required in order that the uP controls the return to the no error Biner Dominik Diploma thesis page 53 78 ooo Power supply and motion system for planetary rover M VALAIS H e S so WALLIS C gt en w gt Tokyo February 20 2008 Chuo University
9. This means that in the scheme fig 8 the current flows from left to right through the motor In case of a rotation in the other side the principle is the same As soon as the transistors S1 and S4 are switched off PWM low the current has to continue to flow in the same direction Thus during the dead time the current flows through the diodes D2 and D3 and into the battery After the dead time S2 and S3 are closed to reduce the losses due to the diodes The losses during the conduction are calculated as follows 1 during PWM high time losses of S1 amp S4 T I with I I rms rms motor T 1085 channel DS on 2 during PWM low time losses of S2 and S3 2a during dead time S1 to S4 switched off 1 Pa U I with La L pao 2 l0S diode Fiiode avg motor T 2b after dead time S2 amp S3 switched on T T sI with I I eE off TOSS channel DS on rms rms motor T Remark The formulas are for the case that the current flowing through the corresponding transistors is a rectangular signal constant motor current Ton represent the high time of the PWM signal Tor the low time For the calculation of the losses during the low time of the PWM signal the value of the average current lag as well as the value of the root mean square current lms depends on how long the MOSFETs S2 and S3 are switched off Tor This means how long the current flows through the diode instead of through the cha
10. from Air Craft 13 Fig 5 Scheme of the arrangement possibility of the voltage regulators case 1 15 Fig 6 Scheme of the arrangement possibility of the voltage regulators case 2 15 Fig 7 Block diagram of the power supply 17 Fig 8 Electrical scheme of an H bridge motor driver for speed regulation 19 Fig 9 Simplified scheme of a MOSFET driving circuit 21 Fig 10 Differential amplifier 25 Fig 11 Modified differential amplifier high common mode voltage 26 Fig 12 Equivalent scheme of the modified amplifier for calculating the input voltage of the OP amp __ 27 Fig 13 Equivalent scheme of the modified amplifier for calculating the voltage Upziow 28 Fig 14 Electrical schema of the battery cell voltage measuring circuit with LM324 31 Fig 15 Electrical schema of the battery cell voltage measuring circuit with LMV324 33 Fig 16 Simulation schema of the battery cell voltage measuring circuit with LM324 36 Fig 17 Simulation result of the battery cell voltage measuring circuit with LM324 36 Fig 18 Driving circuit for the relays used for switching between the charge and the discharge of the batteries switching through analogue circuit possible independent of the microprocessor ___ 38 Fig 19 Truth table switching through analogue circuit independent of the microprocessor 38 Fig 20 NOT gate realised with a NOR gate 39 Fig 21 Picture of the A D converter MAX197 in its simplest operational configuration 41 Fig
11. qagF4oogER kKNGX0O_ XXdphSPgNI4 PPA495 M1 Information about MOSFETs given by the company IRF http www irf com technical info appnotes mosfet pdf http www irf com technical info appnotes an 1005 pdf Information about MOSFETs given by Jonathan Dodge an employee of Microsemi Corporation Applications Engineering Manager http www powermanagementdesignline com 196601551 jsessionid NGUWDMWIASK2KQSNDLOSKHSCJUNNDJVN printableArticle true Tokyo February 20 2008 Signature Dominik Biner Biner Dominik Diploma thesis page 78 78 ooo Power supply and motion system for planetary rover
12. 22 Table for the selection of the analogue input channel A D converter 42 Fig 23 Table for the selection of the voltage range of the analogue inputs A D converter 42 Fig 24 Table for the determination of the full scale input voltage A D converter 42 Fig 25 Reference adjust circuit A D converter 43 Fig 26 Relationship between the internal clock period and the external capacitor A D converter _ 43 Fig 27 Table for the selection of the clock mode A D converter 44 Fig 28 Table with the complete format of the control byte A D converter 45 Fig 29 Used control byte for the conversion of the cell voltage value A D converter 45 Fig 30 Wiring diagram for the conversion of the cell voltage value A D converter 45 Fig 31 Conversion timing if using internal acquisition mode A D converter 46 Fig 32 Linear relation between the output voltage and the measured current LEMLTSR6 NP ____ 47 Fig 33 Choice of nominal current through different connexion schemes LEM LTSR 6 NP 48 Fig 34 Electrical schema of the battery current measuring circuit with LEM LTSR 6 NP 50 Fig 35 Simulation schemes of the battery current measuring circuit with current sensor LEM ___ 52 Fig 36 Simulation result of the battery current measuring circuit with current sensor LEM 52 Fig 37 Simulation result of the battery current measuring circuit with current sensor LEM 53 Fig 38 Driving circuit for the relays used for switchin
13. 9 3 3 General information about lithium polymer batteries From company Air Craft http aircraft world com prod_datasheets hp lipo cl hp Icl Iithium htm e Air Craft lizuka Oroshi Danchi 24 10 Tokuzen lizuka shi Fukuoka 820 0033 Japan Tel 81 0 9 4821 1045 Fax 81 0 9 4821 1040 E Mail shop aircraft world com Homepage www aircraft world com Biner Dominik Diploma thesis page 74 78 ooo Power supply and motion system for planetary rover MN H es s OU WALLIS gt en Jn X Ea Tokyo February 20 2008 IN Chuo University 9 4 Manufacturers of DC DC converter 9 4 1 Lambda Headquarters in Germany Lambda GmbH Karl Bold Strasse 40 D 77855 Achern Tel 49 0 78 416 660 Fax 49 0 78 415 000 Homepage www lambda germany com Domicile in Japan Densei Lambda KK 5F Dempa Building 1 11 15 Higashigotanda Shinagawa ku Tokyo 141 0022 Japan Tel 81 0 3 3447 4693 Fax 81 0 3 3447 4750 Homepage www densei lambda com Sales and distribution For information about suppliers for different countries visit the homepage www lambda germany com http www lambda germany com germany mand pages global_distributio htm 9 4 2 Vicor Headquarters in the USA Vicor corporation 25 Frontage Road Andover MA 01810 5413 Tel 800 735 6200 Fax 978 475 6715 Homepage www vicr com Biner Dominik Diploma thesis page 75 78 ooo Power supply and motion sy
14. Another possibility to measure the current is the use of a shunt resistor In order that not too much voltage falls over the measuring resistance a 10mQ shunt is deployed Therewith with the maximal current of 10 amperes the voltage on the resistance is only 100mV The wattage of the shunt is calculated as follows Fig lA Se Pe SRT shunt nax shunt max shunt shunt pax 4 5 3 1 Use of a differential amplifier Remark Towards the end of the diploma work and my stay in Japan respectively a better solution for amplifying the voltage over the shunt crossed my mind This approach using an inverting amplifier is described in chapter 4 5 3 2 Due to the missing time and that except the manner to amplify the measuring resistance s voltage everything stays the same decided not to remove the approach described in this paragraph Moreover it allows the comparison between the two methods The voltage over the shunt resistor is amplified and relayed to an A D converter to allow the examination of the current by the microprocessor In this paragraph the solution using a differential amplifier is described If the digital signal mentioned at the beginning of chapter 4 5 which signalises when the current exceeds the nominal value has to be generated the amplified voltage is compared to a reference voltage by means of analogue circuits Biner Dominik Diploma thesis page 55 78 ooo Power supply and motion system for planetary rover
15. But this is sufficient as the circuit is identical except for the components values The simulation circuit is as follows 0 0 10k 3 7Vde eig 68k 0 o o Fig 16 Simulation schema of the battery cell voltage measuring circuit with LM324 Only the measure of the topmost cell eighth cell is checked The other seven cells are represented by the voltage source with 30 8Vdc all cells at 4 4V The potentiometer gives the reference voltage of 1 92V which with a gain of 0 6 corresponds to a cell voltage of 3 2V The voltage of the eighth cell is varied from 4 4V to 3 0V and we get the following result H H l 4 4V 4 2V 4 0V 3 8V 3 6V 3 4V 3 2V 3 0V o V UCELL8_MEASURE o V UOUT_COMPARATOR v V VREF V_cell8 Fig 17 Simulation result of the battery cell voltage measuring circuit with LM324 As we can see the output of the comparator gets low as soon as the cell voltage reaches 3 2V and the gain is 0 6 as wished see Probe Cursor window Biner Dominik Diploma thesis page 36 78 at o Power supply and motion system for planetary rover M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University 4 4 2 Other required detections The detection of the start of charge is not sufficient It needs detections of other battery cell voltage values First of all when one battery unit pair is empty the switching to the
16. CA 90245 Tel 1 310 252 7105 Fax 1 310 252 7903 Homepage www irf com Domiciles in Japan International Rectifier Japan Co Ltd Sunshine 60 Building 51st floor 3 1 1 Higashi Ikebukuro Toshima ku Tokyo 170 6051 Japan Tel 81 0 3 3983 0086 Fax 81 0 3 3983 0642 Meitetsu Kanayama Daiichi Building 5F 25 1 Namiyose cho Atsuta ku Nagoya shi Aichi 456 0003 Japan Tel 81 0 5 2871 0570 Fax 81 0 5 2871 0576 KAZU IT Building 2F 2 10 27 Minami Semba Chuo ku Osaka shi Osaka 542 0081 Japan Tel 81 0 6 6258 7560 Fax 81 0 6 6258 7561 Sales and distribution For information about suppliers for different countries visit the homepage www irf com www irf com whoto call salesrep Biner Dominik Diploma thesis page 77 78 Power supply and motion system for planetary rover Y7 NALAIS Hess O waits C tp y x a Tokyo February 20 2008 Chuo University 9 6 Sources for information about MOSFET transistors Book in German online version Title Elemente der angewandten Elektronik Kompendium f r Ausbildung und Beruf Authors Erwin B hmer Dietmar Ehrhardt and Wolfgang Obershelp Publisher Vieweg Verlag published in 2007 15 edition ISBN 3 834 80124 0 The hyperlink to the online version of the book is the following http books google com books id XZLOLZ5ZuKAC amp pg PA56 amp dq isbn 38348012408lr amp as_ brr 0 amp hl de amp sig
17. In the latter case fig 6 all the power is given by the 24V regulator and of course the total amount of losses stays unchanged but therefore the other regulators dissipate less power In other words the distribution of the power on each regulator can be chosen also see examples after fig 6 15t case 24V Voltage o regulator i 12V Voltage l Ubatteries regulator 30Vdc 24Vdc 5V Voltage weve regulator 5Vdc mer Fig 5 Scheme of the arrangement possibility of the voltage regulators case 1 2 case 24V Voltag regulator 12V Voltag regulator 30Vde ak Ubatteries 24Vdc 5V Voltage 12Vde regulator 5Vdc Fig 6 Scheme of the arrangement possibility of the voltage regulators case 2 Biner Dominik Diploma thesis page 15 78 ooo Power supply and motion system for planetary rover H es s O N WALLIS gt p w Je Ea Tokyo February 20 2008 chschule Westschu Chuo University Here two examples to explain this conclusion U oa 12V regulator 1 2V U 24 U out 24V regulator 3W available f ex L eigena 2A Te 24V regulator SA st Pr gt I case U n 12V regulator U 24V regulator U eitzbie Wied 12V regulator U 12V regulator U ir 12V regulator I 12V regulator 36 W gt W sea 24V regulator U 24V regulator U su 24 V regulator I 24 V regulato
18. R U pu U u U G U a U kaow o 3 U pu tu U i R R R Ux R R i R R R R R R R R R R R R R R R Ua Ss R R W u R R R R R R R R R R R R R R R R R Biner Dominik Diploma thesis page 28 78 ooo Power supply and motion system for planetary rover M NALAIS Hes so wanie cp Tokyo February 20 2008 o SPRAY Chuo University U RR R HR ER R JtR Ry B R _ U U R R a u R R R R R R R R R R R R R R R R UU RAR R R R CR RJ R R R R R T FR R R R R R R R R gt U pu E U U R Zi R 5 R R R R R R R R R R R R With the formulas for Up and G the necessary values for the resistance R to R4 can not be dedicated because we have four unknown values and only two formulas Thus its necessary to express the voltage Up by means of the gain G With it we get a formula in which only R4 R2 and the gain G are left U U R R gt R R PUR R R R R R R R R R R R R R R R Au gt R R R R R R R R R R R R G ae pei R RI zy _ ay R a iR R i G 1 RR AR R R R E R rl Therewith we can set the resistance R and then calculate the necessary value for Re After that the same can be done for the values of Rs and Rg set Rs and calculate R4 As mention
19. a current of 10 A continuously Generation of 5 12 and 24Vdc without DC DC converters Autonomy of 2 hours with a consumption of 300 h Availability of an emergency shut down Maximal dimensions of one battery unit is 88mm x 175mm x 50mm Charging of the batteries with a current of 1C The most important thing is to keep the batteries in a safe and appropriate condition This means Temperature of each battery pack between 0 C and 60 C Balance between each cell of a battery pack all cells same voltage Protection against over and undervoltage cell voltage within 3V and 4 2V Appropriate charge and discharge of the battery packs Control of the battery current If the temperature of a battery pack exceeds 60 C it s going to explode development of vapour inside the battery pack If the temperature falls under 0 C the cell will be damaged and losses of capacity will occur Capacity losses will also take place if the cell voltage goes beyond the abovementioned limits The operating temperature of the battery packs is at about 50 C 2 2 2 Motor speed control For the motion and the steering of the rover 12V DC motors from Maxon are deployed A max series They are equipped with a planetary gear and an encoder The type of motors along with the gear and the encoder has already been chosen before the datasheets are on the enclosed CD appendix 5a and 5b The type with 11 watts appendix 5a is used for the motion of the ro
20. as the current has to be controlled While charging the control of the temperature can be realised by means of the charging unit 1210i with the corresponding temperature sensor During the discharge of the batteries it has to be done by the logical unit for example a microprocessor which also takes care of the above described actions and therefore controls all the process This control unit gets the necessary information from different sensors and from measuring circuits respectively Thus for the measure of the temperature during the discharge either the sensor of the charger will be used or if it s not possible another sensor has to be installed The current is measured with a current sensor from the company LEM The current value is transmitted to the control unit so that it knows what happens and can decide what to do Some detection can be realised by means of analogue circuits which only transmit a logical signal to the control unit For example at the end of the charge the logical unit gets the order to disconnect the chargers and balancers by a logical signal OV or 5V Anyway the values of the current and the temperature have to be transmitted to the control unit so that if any value exceeds the nominal rate it can react before they reach critical values Moreover if an error occurs it can be dedicated what happened before Biner Dominik Diploma thesis page 14 78 ooo Power supply and motion system for planetary rover
21. battery with constant power and stops automatically when the batteries are full cell voltage at 4 2V The maximum power delivered by this charging unit is 180W This is enough to charge the batteries like demanded Due to this power limitation the maximal current which can be delivered in our case is 7 5 amperes when each cell is at 3V Of course this value depends of the power given by the solar cells which are used to supply the charger The supply voltage of the charger has to be constant and between 12V and 15V Therefore a voltage regulation of the output voltage of the solar cells is required see chapter 4 2 There is also a temperature sensor available for this charger which allows monitoring the temperature of the battery packs on the charger s LCD Display Moreover the temperature at which the charger should stop to charge can be set between 10 C to 55 C As we have 4 times 2x4S packs we need four chargers Biner Dominik Diploma thesis page 11 78 ooo Power supply and motion system for planetary rover VALAIS He gt soW WALLIS S ib w gt Tokyo February 20 2008 Chuo University Fig 2 Picture of the charger EOS 1210i Remark The start of charge can not be done automatically Some buttons of the chargers have to be pressed manually There are no chargers on the market which allow starting the charge without a manual command because the charge of lithium polymer batteries
22. can be seen by using voltage regulators for the generation of the different voltage levels the efficiency is very bad especially when the 12V regulator has to deliver much current For the first example the total efficiency is only 68 6 Pin 210W Pout 144W and for the second example only 51 4 Pin 210W Pout 108W Biner Dominik Diploma thesis page 16 78 ooo Power supply and motion system for planetary rover NALAIS H e S S o WALLIS en Tokyo February 20 2008 2s so SPRAF Chuo University 3 3 5 Block diagram of the power supply The values voltage current and power are given for charging the batteries with maximal possible current This means that every charger consumes 180 watts U 12 15 V U 12 15 V I 48 60 A I 24 30 A P 720 W P 360 W voltage regulation Solar Cells Vdc Lithium Polymer battery pack 4 8 Ah 4 cells 30Vdc 4 8 Ah balancer Lithium Polymer LBA10 battery pack Master 4 cells 4 8 Ah Lithium Polymer battery pack 4 cells 4 8 Ah 30Vdc 4 8 Ah balancer LBA10 Master Lithium Polymer battery pack 4 cells 4 8 Ah Fig 7 Block diagram of the power supply Remark The two 30Vdc outputs are connected together in parallel Therefore the capacity adds up to 9 6 Ah These outputs represent the input
23. capacitance and resistance which constitute the filter can be chosen smaller because the cut off frequency is determined by the bigger resistance Moreover by using a potentiometer for the resistance R4 the gain can easily be adjusted manually The circuit of the inverting amplifier with low pass filter is as follows R R U U with Gain G R R 1 1 f with f cut off frequency 2m R Fig 47 Differential amplifier with low pass RC filter First the determination of the resistance values For the LM324 G 25 with a value of 3kQ for R the highest accuracy is reached With a gain of 45 rail to rail amplifier a value of 1 5KQ brings out the best C22 S RGR R 1 R 3kQ gt R 75kQ Is real R gt G R Joes RER R 1 R 15kQ R 67 5kQ E12 R 68kQ ww real R gt Gea 45 3 R Biner Dominik Diploma thesis page 61 78 ooo Power supply and motion system for planetary rover DN H es s O WALLI C gt p Jh X Ea Tokyo February 20 2008 IN Chuo University Now the capacitor s value is calculated The cut off frequency is set to 10Hz and we get the following capacity value 1 pesi R 75kQ 2m R C gt 6s on E12 C 220nF 2m R f gt Sareal un 9 65Hz 2 R C 2 fia EHER R 68kQ 20 RG gt ERBE BERE E12 C 220nF mR gt fora a 10 64Hz 2m R
24. cell2 AR 3 7Vde cellt Fig 14 Electrical schema of the battery cell voltage measuring circuit with LM324 Biner Dominik Diploma thesis page 31 78 On Power supply and motion system for planetary rover 7 7 NALAIS i Hes so wanie ch Tokyo February 20 2008 o SPRAY Chuo University As mentioned for the final realisation of the cell voltage measuring circuit the SMD components LMV324 and LMV339 are deployed The use of the LMV324 causes changes to the resistances values and thus their calculation is done as well In this case the maximal input common mode voltage is 4V and hence the voltage U is set to 4V The maximal output voltage is 4 6V and the highest cell voltage to be measured is 4 4V Therefore the gain can be set to 1 in order to reach a big voltage range ge eii U in The highest possible voltage for U see fig 11 stays unchanged and is 35 2V Now the value of the resistance Re can be calculated by setting the value of R In order to get values of the series E12 and that the voltage U is slightly under 4V the resistance R is set to 47kQ R gt U 4 U 35 2V G 1 2 0 p U G P R 47kQ R 6 912kQ E12 R 6 8KQ R 2 3 95V U ur 3 95V Se nn Rirn real gt For the resistances R3 and Rag the choice of Rz 1 1kQ brings out the best _ R R SR HERR R Ri R Rs R R R R R R i R 2 R 1 1kQ g
25. for the voltage level generation Ubatteries in fig 5 and fig 6 The lower part with the 4 balancers and the 4 battery packs is required a second time for the other pair of chargers Biner Dominik Diploma thesis page 17 78 anid o Power supply and motion system for planetary rover 7 7 NALAIS i Hes so wanie ch Tokyo February 20 2008 o SPRAY Chuo University 3 3 6 List of required material elements For realising the abovementioned approaches it needs following components e 8 lithium polymer battery packs with 4 cells and 4 8Ah each e 4chargers 1210i with 4 temperature sensors e 8 balancers LBA10 with the appending cables o 8 times the balance harnesses for 4S batteries o 4 network cable adapter sets for connecting two balancers together e 8 relays with 2 change over contacts each for switching between the charge and the discharge of the batteries as well as 8 bipolar transistors to drive the relay s coils the transistors can be switched by the microprocessor e 2 power MOSFET transistors for connect disconnect the power supply of the chargers To be able to choose which two units are used together in parallel not implicitly always the same two together 4 power MOSFET transistors are necessary in order that the power supply of each charger can individually be connected or disconnected e 4 current sensors for controlling the current drawn or delivered by each battery unit
26. from the HES SO for taking time for my questions and for his very helpful answers Professor Yasuharu Kunii for allowing me to work in his laboratory The HES SO for the financial support Biner Dominik Diploma thesis page 72 78 ooo Power supply and motion system for planetary rover NALAIS a Hes so wiis cp m pas Tokyo February 20 2008 jaliste SS IN K F Chuo University 9 List of references and other links 9 1 References used in paragraph 1 1 K lizuka Y Sato Y Kuroda T Kubotaa Study on Wheeled Forms of Lunar Robots for Traversing Soft Terrain amp Study on Wheel of Exploration Robot on Sandy Terrain technical reports study results Turkey China 2006 See appendix 1a and 1b 2 Eugen Machold Study on landmark tracking using line scanned stereo images diploma thesis report Chuo University Japan HES SO Sion 2006 3 Oral communications with students of the Human Machine Systems Laboratory Dr Eng Kojiro lizuka and Dr Eng Yasuharu Kunii Chuo Univerisity 2007 9 2 Companies Agencies involved in this project 9 2 1 Human Machine Systems Laboratory HMSL HMSL Chuo University 1 13 27 Kasuga Bunkyo ku Tokyo 112 8551 Japan Tel 81 0 3 3817 1866 Fax 81 0 3 3817 1847 E Mail Professor Kunii kunii hmsl elect chuo u ac Homepage http www hmsl elect chuo u ac jp 9 2 2 Japan Aerospace Exploration Agency JAXA J
27. low The minimum pulse width of the signals for CS and WR are 80ns WR and RD control the write and read operations more later CS is the standard chip select signal which enables the uP to address the MAX197 When high it disables the WR and RD inputs and forces the interface into a high impedance state The result of the conversion is readable on the pins 7 to 14 see fig 21 HBEN is used to multiplex this 12 bit result on the data bus When low the 8 LSBs DO to D7 are available on these pins else the 4 MSBs How you can see in figure 21 the 4 MSBs D8 to D11 are put on the data bus instead of DO to D3 and in unipolar mode only positive voltage range see fig 23 the remaining pins D4 to D7 are set low As aforementioned there is a control byte used to configure the device and for choosing the analogue input channel The control byte is latched into the device on DO to D7 pins 7 to 14 during a write cycle This write operation is necessary to start a conversion and is described later in chapter 4 4 4 1 2 The following figure shows the complete format of this byte MSB Most Significant Bit It s the bit in a binary number having the greatest value in general leftmost of the number Biner Dominik Diploma thesis page 44 78 ooo Power supply and motion system for planetary rover H e S a soW nn C pak Ss Tokyo February 20 2008 sac waned Chuo University vwa w ose PD1 PDO
28. maximal capacity See chapter 4 5 5 e Development of the temperature control by the microprocessor In this context it has to be decided if the temperature sensor of the charger is used or if another sensor with a better accuracy is installed Anyway it has to be defined how the sensor is mounted on the battery packs to get an efficient and reliable temperature measure Furthermore the necessary actions in case of a critical temperature value have to be defined Same as for the battery cell voltage and current control it has to be decided if uP independent securities are installed See chapter 4 6 e Final realisation of all circuits by a laboratory with the appropriate infrastructure by using SMD components e Programming of the microprocessor SH 2 used as control unit Among others o Control of the A D converters and treatment of the values provided by them o Calculation of the battery s capacity e Depending on the power consumption of each level the choice of DC DC converters for generating the different voltage levels 5Vdc and 24Vdc has to be done Moreover if the consumption of the 24V level is low enough it can be considered to use a voltage regulator for the generation of the 24V See chapter 4 3 e Choice of the additional battery for assuring that the microprocessors the measuring circuits and the motors used to move or to extend the solar cells are supplied in case that all battery units have to be char
29. motor driver for speed regulation As switches MOSFET transistors are deployed The realisation of this circuit is done by another student of this laboratory by Shimanuki Toru This paragraph serves to give him some first information about the circuit and about the switching of MOSFET transistors because this is not part of his major subject Therefore will continue to assist him in case of questions or problems and help him with the choice of components Moreover help him with the performance of tests but the results are not documented in this report The most important thing is to ensure that never both transistors of one side are switched on at the same time because this would short circuit the battery Therefore after the transistors S1 and S4 have been switched off and the PWM signal goes low respectively a certain amount of time the so called dead time has to be awaited before turning on the other two transistors S2 and S3 to assure that S1 and S4 are completely open The same is necessary for the following switching of S1 and S4 This time depends of the total gate charge of the MOSFETs and the current available for switching the transistors Biner Dominik Diploma thesis page 19 78 ooo Power supply and motion system for planetary rover y H es s O WALLI gt en Jn lt Ea Tokyo February 20 2008 IN Chuo University The necessary switching time can be calculated as follows Oo gs t
30. motors used to move and steer the rover are directly driven with the battery voltage see chapter 3 4 So the only additional voltage level necessary is 5Vdc for supplying the microprocessor and the integrated circuits To generate this two voltage levels DC DC converters are deployed because how shown in chapter 3 3 4 voltage regulators cause too much losses Because the power consumption of each level is not defined now the choice of appropriate DC DC converters isn t done yet Links to manufacturers of DC DC converters are listed in chapter 9 4 If the consumption of the 24V level is low enough it can be considered to use a voltage regulator for the generation of the 24V Because the efficiency of the 24V regulator is at about 75 to 80 and thus if the delivered power is low the wastages as well as the heating of the device are small too Of course even in this case the use of a DC DC converter causes fewer losses of power but it s bigger and more expensive For the circuits described in the following chapters the 24V voltage is only used for the relays that switch between the charge and the discharge of the batteries see paragraph 4 4 3 1 The losses due to the relay and the bipolar transistors for driving their coil have already been calculated and are the following for the relay from the company Finder Paian 1 694W relay P 21 2mW trans Overall it has eight relays and eight transistors Therefore the total amount
31. of power drawn Biner Dominik Diploma thesis page 24 78 ooo Power supply and motion system for planetary rover VALAIS 1 Hess SO M WALLIS cp Tokyo February 20 2008 J SFAXE Chuo University from the 24V source by the circuits is the following Poy circuit S 8 Pu P 13 72W trans With an input voltage of 30V the regulator s efficiency is 80 So now it depends on how much power is required for the ultrasonic motors For example with consumptions of 30W or 100W the losses of the regulator are as follows U 24V regulator 30V U os 24V regulator 24V gt AU 6V P P motors 30W gt Ena 24V regulator 43 72W out 24V regulator motors 24V circuit CE naor 100W gt F 24V regulator z 1 13 72W I Er 24V regulator P m tors 30W gt Ts 24V regulator 1 82A out 24V regulator out 24V regulator P rors 100W gt Lu a ae 474A E m 30W gt Epi 24V regulator 10 93W loss 24V regulator AU Los 24V regulator Proors 100W gt F 28 43W loss 24V regulator 4 4 Battery cell voltage control 4 4 1 Measure of the cell voltages detection of the start of charge While discharging not every cell is at the same voltage and so it s necessary to measure and control the voltage of each cell As soon as one battery cell reaches 3 2 volts the battery pack has to be charged The cell voltages are measured with differential amplifie
32. of the electronic circuits PCB 65 5 1 1 Cell voltage measuring circuit 66 5 1 2 Current measuring circuit 67 Test of the electronic circuits PCB 68 6 1 1 Cell voltage measuring circuit 68 Conclusion 68 7 1 Work performed 68 7 2 Work to be undertaken future tasks 69 7 3 Major difficulties encountered during this diploma work 71 7 3 1 Personal statement 71 8 Acknowledgments 72 9 List of references and other links 73 9 1 References used in paragraph 1 73 9 2 Companies Agencies involved in this project 73 9 2 1 Human Machine Systems Laboratory HMSL 73 9 2 2 Japan Aerospace Exploration Agency JAXA 13 9 3 Sources for the choice of LiPos and charging equipment 74 9 3 1 Company Hyperion 74 9 3 2 Manuals of charging equipment 14 9 3 3 General information about lithium polymer batteries 14 9 4 Manufacturers of DC DC converter 75 9 4 1 Lambda 75 9 4 2 Vicor 75 9 4 3 Deutronic 76 9 5 Manufacturer of MOSFET drivers IRF 77 9 6 Sources for information about MOSFET transistors 78 Biner Dominik Diploma thesis page 2 78 DN H es s O WALLI gt p Jh Je Ea Tokyo February 20 2008 IN Chuo University Illustration listing Fig 1 Sketch ofthe new wheel placement use of circular and pentagon shaped wheels 9 Fig 2 Picture of the charger EOS 1210i 12 Fig 3 Picture of the balancer EOS LBA10 12 Fig 4 Discharge curves of a CL 1S 2100mAh with different discharge current values
33. of the maximal output current of the NOR gate the basis current is set to 12mA Thus for the drive resistance we get following value DPDT Double Pole Double Throw This type of relay has two rows of change over terminals Biner Dominik Diploma thesis page 39 78 ooo Power supply and motion system for planetary rover F Chuo University NALAIS i Hes so wais ch pas Tokyo February 20 2008 a SPRA oa AV Ar 50 Upp 0 7V I 1 Finder I 70 6mA gt JI 10 14 12mA I 12mA FE cae U pr gt R e 2759 I gt El2 R 270Q I 2 Omron I 36 9mA gt JI 10 7 38mA FE U pu zZ U pr gt R 4709 I gt E24 R 430Q As the coil is energized with DC a diode is installed across the coil to dissipate the energy from the collapsing magnetic field at deactivation This is to protect the transistor from the voltage spike that would be generated by the coil For it the diode 1N4002 is used 4 4 3 2 Too high cell voltage charge process As defined in chapter 3 3 6 power MOSFET transistors are deployed for connecting or disconnecting the power supply of the chargers Such as for the double security against a too low cell voltage the stopping of the charge can be done by actuating the transistor so that the chargers are no longer supplied Again the signal provided by the analogue circuit see fig 15 is used to switch off the transistor But the MOSFE
34. or 8 if the batteries are not in series during the charge process in order to measure the current of each battery pack Or shunt resistors either 4 or 8 for measuring the charge current and 4 for measuring the discharge current or only 4 or 8 if both current senses are measured with the same resistance positive and negative voltage on shunt resistor e A cell voltage measurement and monitoring system e A temperature measurement and surveillance system e A microprocessor as control unit e A powerful voltage regulation up to 720W for generating the supply voltage for the chargers from the solar cells DC DC converter e DC DC converters and or voltage regulators for the generation of the different voltage levels 5V 12V and 24V 3 4 Motor speed control As mentioned in chapter 2 2 2 the 12Vdc motors have to be driven directly with the battery voltage Depending of the charge level of the battery the voltage varies between 24Vdc and 33 6Vdc For the regulation of the motor speed an H bridge will be used as motor driver see figure below fig 8 Therewith the motor can be actuated directly with 24Vdc to 33 6Vdc without the need of a very high or low duty cycle of the PWM signal Moreover a part of the motor current flows back into the battery Therefore in average less current is drawn and hence less of the battery s capacity used Change over or double throw contact also called transfer contact means one norma
35. other two battery units is only possible if they are adequately charged Therefore while charging the voltage of each battery cell has to be transmittable to the microprocessor uP by means of an A D converter so that it can decide if either the switching is possible or if all the battery units have to be charged But if the voltage of a cell stays constant during the most time of the charge process additionally the capacity of the battery is calculated by the microprocessor by means of a current and time measure The conversion of the analogue signals provided by the cell voltage and current measuring circuits is realised by the A D converter MAX197B It provides a 12 bit digital signal that can be read by the uP Further about the use of this converter see paragraph 4 4 4 In case that all the units have to be charged no more power source is available and the rover has to stop and wait at least until one battery unit pair is charged The occurrence of this case can be problematic if the rover is in a critical position for example is climbing up a slope For that reason it s necessary that the microprocessor knows that the batteries are going to be empty This means that it has to be able to determine the battery s capacity such as for the detection described before deciding if a battery unit is adequately charged to be switched to the load Hence this case can also be detected through the measure of the cell voltages As aforementioned the
36. parts in order to guarantee an autonomy time higher than the required time for charging the other batteries Of course the development of the battery s voltage regulation isn t done now too but prospectively the same voltage regulators and DC DC converters respectively as for the generation of the different voltage levels are used see chapter 4 3 Moreover a method for charging it has to be developed and finally the concept for the switching of the battery has to be set up connection and disconnection of the battery from the load charger 5 Manufacturing of the electronic circuits PCB As mentioned the final realisation of the circuits has to be done by a laboratory with the appropriate infrastructure and in order to be more space saving with SMD components But for allowing to make first tests some circuits are realised in this laboratory nevertheless The PCB is drawn with the software Opuser With this program the creation of schematics electrical schemas is not possible and therefore the PCB layout has to be drawn directly This hampers the work and hence it takes up more time Another disadvantage is that it s not possible to create a bill of material as well as an implantation scheme Moreover the ground plane has to be done manually Fortunately most components have already been created by other students of the laboratory and are available in a library The manufacturing of the PCB isn t done with chemical products The ma
37. security is realised by detecting if a cell reaches 4 4V The cell voltages are transmitted to the microprocessor and thus this detection can also be taken over by it But it has to be decided if it s necessary that the consequential actions e g stop of the discharge have to be independent of the uP and therefore have to be taken over by analogue circuits If yes for a too low cell voltage a double security is realised as well This means that a cell voltage of 3 0V is also detected to assure that the battery is not damaged Biner Dominik Diploma thesis page 37 78 ooo Power supply and motion system for planetary rover 7 7 NALAIS i Hes so wani ch Tokyo February 20 2008 o SPRAY Chuo University 4 4 3 Double securities How aforementioned if the double security is taken over by the microprocessor only the detection of a voltage of 4 4V is done and it doesn t need additional circuits Else the detection of the two values 3 0V and 4 4V has to be done with the circuit shown in figure 15 including the comparators Only the comparators and the potentiometer to generate the different reference voltages are required two times 4 4 3 1 Too low cell voltage discharge process The signal provided by the comparators is TTL compatible OV or 5V and therefore can be used to drive logical gates The signal goes low when the voltage of one cell falls under the reference voltage thus under 3 0V As d
38. should not be unattended Therefore the charger will have to be modified This means that the corresponding buttons have to be replaced by bipolar transistors which can be driven by the microprocessor Due to the missing time the infrastructure and the missing specialists in this domain the development of a charger during this diploma work is not possible Moreover it would most likely be more expensive as the charger mentioned above But it could be realised more space saving Anyway to make the first tests the necessary equipment to charge one battery unit two 4 cells packs in series is already ordered see appendix 3 To balance the cells the balancer EOS LBA10 is used It is compatible with the charger mentioned above and gives the possibility to monitor the battery voltage on the charger s display With it up to 6 cells can be balanced while or after charging Thus in our case we need to connect two of them together to be able to balance the 8 cells So overall we need 8 balancers 4mm Gold plugs to DataPort Charger Output Port to view Eprogs po Solder on your charger preferred battery LCD connector here harnesses attach here Network two LBA10 via Port HYPERION Network here to balance LBA10net 6S in 7Sto 1s Fig 3 Picture of the balancer EOS LBA10 For more information about the charger and the balancer see the extract from the Hyperion product catalogue attached to this rep
39. students also at the Tama Campus But due to the limited time after November 5 don t give these lessons anymore Task Week Information gathering about planetary rover A Information gathering mation contol fotos ML I I I I II III est of motor speed regulation with motor driver EHE BEEBEHZEBEBE EB BE BHO Dimensioning of the motor driver for speed regulation search of components for H bridge and write description of the circuit for Shimanuki Toru SR REPRE eRe 5 a S 8 Analyse of the wheel s form and make suggestion for a new wheel placement i a a Se FS ea HE SI Choice of battery packs Choice of battery charging equipment Development of the power supply approaches u ae ae Te en E Eu Eu battery cell voltage and battery current Setting up concepts for the battery cell voltage and ele YT yyy f i battery current control Dimensioning of the circuits concerning these concepts Sau BADE DEDE and fabrication of the required connectors cables n BE measuring circuit EEE Mm T control and search of appropriate temperature sensors Realisation ofthe presentation grene 15072008 I II II COOC O Realisation of the final presentation given in Japan the NERENNHERNHORARENENNE 22 of February 2008 ST EEE Switzerland March 2008 Rept Only 2 days of work per week Holiday Illness Biner Dominik Diploma thesis page 8 78 10 Power supply and motion system for planetary rover
40. the time and draw a very small current Inom 0 2A Therefore for the speed regulation of these motors it s easier to actuate the H bridge differently use of the bridge as a buck converter This means that the PWM signal is only applied to the upper transistors S1 and S3 The lower transistors S2 or S4 are permanently switched on For example for moving forward the switch S4 is continuously closed and the PWM signal is applied to S1 The transistors S2 and S3 are not used and stay switched off But like before after opening S1 and after awaiting the dead time the transistor S2 can be switched on for reducing the losses due to the diode In this case the duty cycle is calculated as follows Biner Dominik Diploma thesis page 21 78 ooo Power supply and motion system for planetary rover 7 7 NALAIS i Hes so wanie ch Tokyo February 20 2008 o SPRAY Chuo University m m os or a dutycycle T period of PWM signal DCmotor U pan U gt m DCmotor U pan a U pan 24V U enot 12V gt m 0 50 b U pan 33 6V U bnon 12V gt m 0 36 Remark In this case the duty cycle for moving forward is the same as for the other direction The duty cycle changes between 0 stand still and 50 full speed Calculation of the losses due to the MOSFETs The following description is for the case that the PWM signal is applied as shown in figure 8 and when the motor is used to move forward
41. to be generated the output voltage is compared to a reference voltage by means of analogue circuits Comparators are also necessary for the realisation of the uP independent security measures described in the following chapter As comparator the LMV339 is deployed and the reference voltage is given with a 1MQ potentiometer same as for the cell voltage control The circuit for the current measure including the comparators is the following 5Vdc 10k 10k 5Vdc Idischarge gt 10A 10k 10k Inominal exceeded Icharge gt 7 7A 1Mt Fig 34 Electrical schema of the battery current measuring circuit with LEM LTSR 6 NP Remark The signals delivered by the comparators get low in case of an error viz when the current exceeds the nominal value and the maximal value respectively Therefore the comparator outputs only draw current in that case The upper two comparators are for the discharge current and the lower ones for the charge current The signal lavg is relayed to the A D converter MAX197 for transmitting the current value to Biner Dominik Diploma thesis page 50 78 ooo Power supply and motion system for planetary rover NALAIS a Hes so wiis tp m pas Tokyo February 20 2008 jaliste SS 7 K F Chuo University the uP or also the signal TILEM to allow the determination of the maximal current value The reference voltages for the discharge current are given fo
42. voltage But anyway the power supply would have to be set to 2 7Vdc and this causes different problems The maximal output voltage of the LMV324 is only 2 6V and the input common mode voltage Vcm of the LMV339 can only be 2V at most Therefore the accuracy of the measure decreases as the available voltage range is smaller Remark During the discharge due to the speed regulation of the motors see chapter 3 4 the current is also flowing into the battery Therefore the voltage over the shunt resistance during the discharge can be positive or negative and the use of one shunt resistor for each charge and discharge process doesn solve this problem Due to the missing time the search of appropriate SMD components isn t done during this diploma work especially also because the current measure with a shunt resistance requires a negative supply voltage and suggest using a current sensor from LEM But the circuit is dimensioned for the use of the components LM324 and LM339 They are available with SMD package and can be supplied with 5Vdc But as mentioned in chapter 4 4 1 the LM324 s maximal output voltage is only 3V Thus in order to reach a bigger voltage range of the measured signal for the final realisation a rail to rail amplifier is deployed But this only implicates an adaption of the differential amplifiers gain For the use of the LM324 the gain is set to 25 so that with the maximal current of 10A the output voltage is 2 5V W
43. voltages measured with the differential amplifiers as shown in figure 15 are transmitted to the microprocessor The microprocessor takes care of the detection of the appropriate cell voltage value which indicates that the battery is going to be empty This value is depending on how the batteries are discharged see fig 4 and has to be dedicated by tests Such as for the determination of the battery s charge level additionally the remaining capacity can be estimated by means of a current and time measure during the discharge Remark Furthermore in case that all the battery units have to be charged the uP the measuring circuits as well as the motors for moving extend the solar cells have to be supplied Therefore it needs an additional battery to ensure this For the processor and the measuring circuits a 2 cell lithium polymer battery is sufficient for delivering the required 5V But depending on the voltage needed for the motors deployed to move or to extend the solar cells more cells are necessary Further about the additional battery see chapter 4 7 Finally for protecting the batteries the detection of a too high cell voltage has to be realised The detection of a low cell voltage 3 2V is already done by the uP to determinate the start of charge see chapter 4 4 1 As mentioned in chapter 3 3 3 the detection of the end of charge battery cell voltage at 4 2V is done by the charger 1210i But to be independent of the charger a double
44. 24 25 23 4 4 1 1 Simulation of the circuit 36 4 4 2 Other required detections 37 4 4 3 Double securities 38 4 4 3 1 Too low cell voltage discharge process 38 4 4 3 2 Too high cell voltage charge process 40 4 4 4 Use of A D converters for the cell voltage control 40 4 4 4 1 How to use the converter MAX 197 description of the device 4 5 Battery current control 4 5 1 Current measure with current sensor from LEM 41 46 47 4 5 1 1 Simulation of the circuit 52 4 5 2 Security measures uP independent 53 4 5 2 1 Too high current during the discharge process 53 4 5 2 2 Too high current during the charge process 55 4 5 3 Current measure with shunt resistance 55 4 5 3 1 Use of a differential amplifier 55 4 5 3 2 Use of an inverting amplifier 61 4 5 3 3 A D conversion with the MAX197 63 Biner Dominik Diploma thesis ooo Power supply and motion system for planetary rover page 1 78 Hes so wit CPRAF Chuo University Tokyo February 20 2008 ooo Power supply and motion system for planetary rover 4 5 4 Comparison between the different measuring methods 63 4 5 5 Detection of the end of charge 64 4 6 Battery temperature control 64 4 7 Additional battery 65 Manufacturing
45. 2C Weight 384gr Size 34 x 102 x 51 mm Remark There are two series of battery packs provided by Hyperion the VX LiPo packs blue series and the CL LiPo packs red series In our case it s better to use batteries from the red series CL stays for capacity and low weight light For more information see the extract from the Hyperion product catalogue attached to this report appendix 2 In order to reach an autonomy time of about 2 hours the total available capacity has to be 20Ah 30V t 2h P sea 300W U autonomy 600Wh gt W used nominal W reeded P used EN Q needed needed capacity W ceded Q needed U omal W gt Q needed needed 20Ah nominal Therefore it needs at least 4 units of 2x4S packs so overall 8 battery packs Therewith we Biner Dominik Diploma thesis page 10 78 ooo Power supply and motion system for planetary rover M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University reach a total capacity of 16 8 Ah and 19 2 Ah with the 4800mAh type respectively As it can be seen the difference in weight is quite high compared to the difference in capacity The 4800mAh type has a capacity weight ratio of 9 3mAh per gram the other one 10 9mAh per gram But if we analyse the difference it brings in energy see below it s definitely better to use batteries with a capacity of 4800mAh 260gr difference gt totally 1 04 kg mo
46. 4 492 LSBs Moreover by reducing the reference voltage the ratio of the RMS noise to the LSB value increases which results in performance degradation loss of effective bits Thus in our case the REF and the REFADJ pin is not connected like shown in figure 21 The REF pin is bypassed to GND with a 4 7uF electrolytic capacitor and the REFADJ pin with a 8 The full scale input range determine which voltage value corresponds to the highest possible digital value Biner Dominik Diploma thesis page 42 78 ooo Power supply and motion system for planetary rover M H es s OU WALLIS gt p Jh Je Ea Tokyo February 20 2008 IN Chuo University 0 01uF capacitor The internal reference voltage is adjustable to 1 5 with the reference adjust circuit shown below fig 25 Therewith the voltage VREF can be set exactly at 4 096V in order to reach the best accuracy MAAXLAA MAX197 REFADJ Fig 25 Reference adjust circuit A D converter The signal INT on pin 24 goes low when a conversion is completed and the data is ready to be read The microprocessor can use this signal to determine when the conversion is done The power supply Vpp pin 27 has to be bypassed to ground with a 0 1uF capacitor to compensate fast voltage fluctuations The additional 4 7uF electrolytic capacitor showed in figure 21 is also used to assure a constant supply voltage This one minimises the low frequency fluctuation
47. AXA headquarters in Chofu city 7 44 1 Jindaiji Higashi machi Chofu shi Tokyo 182 8522 Japan JAXA Tokyo Office Marunouchi Kitaguchi Building 1 6 5 Marunouchi Chiyoda ku Tokyo 100 8260 Japan Tel look on the homepage for the phone number of the appropriate department Homepage http www jaxa jp index_e html Remark Since October 1 2003 the Institute of Space and Astronautical Science ISAS National Aerospace Laboratory of Japan NAL and National Space Development Agency of Japan NASDA were merged into one independent administrative institution the Japan Aerospace Exploration Agency JAXA Biner Dominik Diploma thesis page 73 78 ooo Power supply and motion system for planetary rover M VALAIS Hes so wais cp Tokyo February 20 2008 o SPRAY Chuo University 9 3 Sources for the choice of LiPos and charging equipment 9 3 1 Company Hyperion Hyperion Europe Stamholmen 153 DK 2650 Hvidovre Tel 45 0 70 270 630 Fax 45 0 70 270 640 E Mail info hyperion europe com Homepage http www hyperion eu com Product catalogue http www hyperion eu com public hyperion eu pdf 9 3 2 Manuals of charging equipment Hyperion charger 1210i http www hyperion eu com public manuals EOS1210i MAN ENG pdf Hyperion balancer LBA10 http mysite verizon net vze2gbfc sitebuildercontent sitebuilderfiles lba10 pdf Cell meter http www ep plane com cellmeter
48. Biner Dominik NALAIS H e S S o WALLIS en Tokyo February 20 2008 28 S0 SPRAY Chuo University With a rail to rail amplifier the reference voltages and the components values change Oto the load battery f T 820n Imess 10k 10k 5Vdc Inominal exceeded Idischarge gt 10A ref 2 25V 9 5Vdc 5Vdc A 10k 10k 5Vdc Imess 9 Inominal exceeded IMS__ref 3 465V8 Fig 44 Electrical schema of the battery current measuring circuit with shunt and rail to rail amplifier Icharge gt 7 7A 5Vde Remark The comparators are used to generate the digital signal that signalises when the current exceeds the nominal value and for realising the uP independent security measures described in the previous chapter The signals get low when the current exceeds the reference value so that the comparator outputs only draw current in that case The upper two comparators are for the discharge current and the lower ones for the charge current For the reference voltage values for the discharge current the same problem as described before for the measure with the current sensor is existing see chapter 4 5 1 page 51 The signal Imess is relayed to the A D converter MAX197 for transmitting the current value to the uP further about the use of the converter in this case see paragraph 4 5 3 3 The power dissipation of the resistances i
49. C Concerning the reference voltages for the comparators everything stays the same Such as with the differential amplifier the amplified voltage is positive for a discharge current and negative for a current flowing into the battery 4 5 3 2 1 Simulation of the circuit To verify the functionality of the circuit a simulation with the software OrCAD is done The simulation circuit is as follows Ushunt Fig 48 Simulation schema of the battery current measuring circuit with shunt and LM324 To check the functionality of the filter the voltage on the shunt resistance is represented with the AC voltage source V12 The source provides a sinusoidal signal with amplitude 100mV The frequency of the signal is varied from 0 1Hz to 100kHz and we get the following result Biner Dominik Diploma thesis page 62 78 ooo Power supply and motion system for planetary rover 7 NALAIS H es s o WALLIS en Tokyo February 20 2008 N SPRAS Chuo University 25 BIER 299 358n 9 736 9 4363 1 6666K 16 666K dif 9 0000K 50 t t 100mHz 1 0Hz 10Hz 100Hz 1 0KHz 10KHz 100KHz o 20 LOG10 V IMESS V USHUNT Fig 49 Simulation result of the battery current measuring circuit with shunt and LM324 On the y axis the amplification in dB is given Aas 20 log A As we can see for low frequencies the amplification is 27 95dB whic
50. HBEN is low the lower eight bits are read else the four MSBs That the conversion is finished and a valid result is available is acquainted to the uP by a standard interrupt signal provided by the converter output INT goes low The signal INT returns high on the first read cycle or if a new control byte is written The following picture shows the conversion timing loan Lot N Ich BYTE ACQMOD Rz te HIGH LOW HGH Z BYTE VALID Fig 31 Conversion timing if using internal acquisition mode A D converter 4 5 Battery current control With the given nominal maximal discharge current of 10A the nominal maximal current drawn from one battery unit is 5A two units in parallel During the charge the nominal current is 4 8A 1C Same as for the cell voltage measure the current value is transmitted to the microprocessor uP through an A D converter If during the charge the two battery packs of one unit should not be connected in series see fig 7 the current of each pack would have Biner Dominik Diploma thesis page 46 78 ooo Power supply and motion system for planetary rover M NALAIS Hes so wanie cp Tokyo February 20 2008 o SPRAY Chuo University to be measured If the supervision of the current during nominal condition has not to be done permanently a digital signal that signalises when the current exceeds the aforementioned values is transmitte
51. Hes so Was CSPRAF Chuo University Studiengang Systemtechnik Vertiefungsrichtung Power and Control Diplom 2007 Dominik Biner Power supply and motion system for planetary rover Dozent Mister Michel Imhasly Experte Dr Eng Yasuharu Kunii Tokyo 20 Februar 2008 Hes so wit CPRAF Chuo University Table of contents 1 General information about planetary rovers Tokyo February 20 2008 2 Structure of this diploma work 2 1 Introduction to my work 2 2 Requirements specification 2 2 1 Power supply 2 2 2 Motor speed control 2 3 Operating schedule 3 Analyses and first approaches 3 1 Introduction to this paragraph 3 2 Optimisation of the wheel s shape 3 3 Power supply Lithium polymer batteries 3 3 1 Selection of the batteries oO oo NNN AA A 10 3 3 2 Selection of the charging equipment 11 3 3 3 Approach how to use batteries and charging equipment 13 15 3 3 4 Approach for the generation of the different voltage levels 3 3 5 Block diagram of the power supply 17 3 3 6 List of required material elements 18 3 4 Motor speed control 4 Realisation suggestions for the power supply 18 24 4 1 Introduction to this paragraph 4 2 Regulation of the solar cells voltage 4 3 Voltage levels generation 4 4 Battery cell voltage control 4 4 1 Measure of the cell voltages detection of the start of charge 24 24
52. If desired necessary a charging unit has to be developed For the use of the charger 1210i from Hyperion the accordant buttons have to be replaced by bipolar transistors to allow the start of charge by the uP only two of them once the configuration number of cells charge current etc has been given it s memorised by the charger even after taking away the power supply See chapter 3 3 2 page 12 Biner Dominik Diploma thesis page 69 78 Power supply and motion system for planetary rover NALAIS a Hes so wiis cp m pas Tokyo February 20 2008 jaliste SS 7 K F Chuo University e Choice of the current measuring method LEM or shunt resistor In case that shunt resistances are used appropriate SMD components for realising the circuit have to be chosen e Decision if the current monitoring is done permanently or if a digital signal is transmitted to the microprocessor as soon as the current exceeds the nominal value current control by uP only if I gt Inominal e Determination of the nominal and maximal discharge current to define the reference values and for the potential adaption of the measuring range of the current sensor or the measuring circuit using a shunt resistance See chapter 4 5 1 to 4 5 4 e Manufacturing and test of the current measuring circuit e Decision if for saving time the charge of the batteries is stopped before they are completely full charge only to 90 of
53. LMV324 5g Comparator LMV339 5h Operational amplifier LM324 5i Comparator LM339 5j Quad 2 input NOR gate M74HCO2 5k Relay from the company Finder Series 66 5 Relay from the company Omron LY2 5m A D converter MAX197 5n Current sensor LTSR 6 NP LEM 50 Quad RS latch 74HC279 5p Quad 2 input AND gate MM74HC08 5q Temperature sensor LM35 Se ae _ 5 Biner Dominik Diploma thesis page 5 78 Power supply and motion system for planetary rover NALAIS a Hes so wiis cp m pas Tokyo February 20 2008 jaliste SS 7 K F Chuo University 1 General information about planetary rovers Nowadays robots are used to explore planets in our solar system They are one of the most important mission devices for planetary explorations 1 The environment on these planets is not well known and therefore it s necessary that a robot can get and treat this information on its own If the rover is able to get steadily new data over its environment it can adjust the path on its own and correct its position information and therefore eliminate long breaks while driving to a waypoint Else breaks are caused by the transmission delay of required orders from the control station on earth Several approaches to this problem were made Almost all of them are based on distance maps produced by stereo vision systems or laser range finder 2 3 Another issue is the motion control of the rover There are different prob
54. T transistors have not been chosen yet among others because the solar cells are not finished developed now and therefore the circuit for driving them is not realised at this point But the principle is the same as for the protection against a too low cell voltage described previously Remark If the comparators are used as shown in figure 15 the signal provided by them will only go high when the voltage of each cell exceeds the reference voltage of 4 4V wired and Moreover the comparator outputs draw a current as long as the cell voltage is under 4 4V But by exchanging the two inputs of the comparator this can easily be changed so that the output goes low as soon as one cell exceeds the 4 4V and the comparator output only draw current in this case Thus for this case the reference voltage is applied to the positive input 4 4 4 Use of A D converters for the cell voltage control By means of A D converters the measured cell voltages are transmitted to the uP This has the big advantage that the microprocessor has the possibility to determine each cell voltage at any time and especially that the detection of any voltage value can be done without the use of additional components Only the differential amplifiers are required to get the voltage of each cell In order not to use one A D converter for each cell the cell voltages are multiplexed to the entry of the converter This is sufficient because the cell voltages don t change so fast As
55. These two bits select the clock and power down modas ACOMOD 0 internally controlled acquisition 6 clock cycles 1 extemally controlled acquisition Selacts the full scale voltage magnitude at the input 3 BIP Selects unipolar or bipolar conversion moda a A1 A0 These are address bits for the input mux to select the on channel Fig 28 Table with the complete format of the control byte A D converter Only the state of the bit D5 ACQMOD has not been defined previously This bit determines the acquisition mode The acquisition can be done internally or externally In our case the internal mode is selected This means that after the write pulse on WR an acquisition interval of fix duration is initiated six clock cycles Therefore the conversion starts when this six clock cycle 3 85us with fe k 1 56MHz ends For more information about the difference between the two modes refer to the datasheet on the enclosed CD appendix 5m page 10 Thus in our case the control byte is as follows PD1 PDo JacamonD RNG BP a2 a1 AO aaa ae a a ee ee Fig 29 Used control byte for the conversion of the cell voltage value A D converter Remark The A s for the bits AO to AT stand for the address used to choose the analogue input channel as shown in the table on figure 22 4 4 4 1 1 Wiring diagram For our application the wiring diagram differs a little from the one showed in figure 21 The voltage reference in
56. and tried to help as good as they could but my research theme was not part of their subject area Moreover they had much work to do themselves and thus didn t want to take too much of their time My person in charge Dr Eng Yasuharu Kunii had much to do too and was very busy most of the time He was also very cooperative and his English skills were quite good But as my research field was not part of his area of expertise either and as he was so busy tried to work as independently as possible 7 3 1 Personal statement In summary have to say that it was very difficult to work under these conditions even impossible to work professionally Especially because the infrastructure was not adapted to Biner Dominik Diploma thesis page 71 78 ooo Power supply and motion system for planetary rover NALAIS a Hes so wiis cp m pas Tokyo February 20 2008 jaliste SS 7 K F Chuo University the tasks was supposed to do Furthermore due to my inadequate Japanese skills the choice of components could not be done as customary The missing contact person was one of the biggest issues Fortunately could ask Mr Hans Peter Biner from the HES SO about some topics But it turned out that it was rather difficult to describe problems and ask questions via email But in my opinion I did all could to bring out the best under the given circumstances However these 6 months here in Japan were a great challe
57. automatically the end of charge and stops charging when cell voltage at 4 2V In addition it puts the balancers in a shut down mode In that state the balancers draw a very small current from the battery packs about 0 5mA Therefore as soon as the current falls down to this value during the charge the batteries are full and the chargers are disconnected from their power supply solar cells The detection of this value is done by the microprocessor by means of the current value transmitted to it by the current measuring circuit Additionally the cell voltage can be checked too if at 4 2V As mentioned in chapter 3 3 2 the charge of lithium polymer batteries is done with constant power This means that towards the end of the charge the current is smaller P U I On this account it can take up to half as much time to charge the last 10 of the battery s capacity as it s required for charging the first 90 Thus it could be advantageous to stop the charge earlier in order to save time The corresponding current value to detect the end of charge in this case has to be determined by tests 4 6 Battery temperature control Due to the missing time the temperature control has not been developed As mentioned in chapter 3 3 3 page 14 the temperature during the charge is controlled by the charger with the corresponding temperature sensor As soon as the temperature exceeds the given value the charge is stopped Unfortunately received this se
58. cause any problem in our application as the battery voltage is regulated Charge 1050mA 0 5C 4 2V 3hrs Cut off Current 210mA 25T Discharge Cut off Voltage 2 5V t 10650mA0 5C 33600mA 16 0C 35700mA 17 0C 37800mA 18 0C 42000mA 20 0C Cell Voltage V 0 400 800 1200 1600 2000 2400 Discharge Capacity mAh Fig 4 Discharge curves of a CL 1S 2100mAh with different discharge current values from Air Craft Of course if all the units would be used together the current drawn from each unit would be divided by four But then all the batteries will be empty at the same time and at this point the rover is obliged to stop his work for charging them Thus to avoid this case under no circumstances all four units are discharged at the same time but of course the four units can be charged at the same time The switching between the two pairs of battery units takes place when one of them is empty and has to be charged If at this point the other pair has to be charged too it s connected to the consumer depending on its charge level even if it s not fully charged To realize the switching following detections are needed Biner Dominik Diploma thesis page 13 78 ooo Power supply and motion system for planetary rover M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University 1 start of charge For detecting when the batteries have to be char
59. chine available in the laboratory uses milling cutters to remove the copper The drilling of the holes is taken over by the machine This method has the advantage that no chemical products are used and therefore it s not necessary to dispose of them But on the other hand the manufacturing takes more time and is less accurate with the machine type existent in the laboratory ProtoMat C60 Biner Dominik Diploma thesis page 65 78 ooo Power supply and motion system for planetary rover VALAIS Hess o WALLIS tp m x a Tokyo February 20 2008 Haute Ecole Sp uisse occ aute cialisee de Suisse occidentale Chuo University 5 1 1 Cell voltage measuring circuit The PCB for the cell voltage measure has been fabricated As mentioned in chapter 4 4 1 for allowing the execution of the first tests the circuit using the LM324 and LM339 DIL package is realised see fig 14 The following picture shows the first version of the PCB Fig 51 Picture of the first version of the cell voltage measuring circuit PCB Unfortunately the copper around most of the holes has been torn away by the borer see fig 51 Therefore decided to make a second version with bigger copper circles around the holes But to change the size of the pads the components of the library have to be modified and then placed again Thus to avoid this by means of the tool for creating the ground plane an appropriate
60. copper circle has been created and has been put over each pin Therewith the problem has been solved and the circuit looks as follows Fig 52 Picture of the second version of the cell voltage measuring circuit PCB Biner Dominik Diploma thesis page 66 78 Power supply and motion system for planetary rover VALAIS Hes so WALLIS C tp y Ke Tokyo February 20 2008 Chuo University While populating the PCB with the required components discovered a mistake The drawing of the PCB is done on the bottom layer and didn t take into account that when mounting the integrated circuits on the top their pins will be exchanged For the LM324 it doesn t matter because it s completely symmetric see fig 53 But the LM339 has to be mounted on the bottom side OUTPUTS INPUTS INPUT 4 GND INPUT 3 INPUT3 gt OUTPUT 3 OUTPUT 3 OUTPUT 4 GND INPUT 4 INPUT 4 INPUT 3 INPUT 3 OUTPUT I INPUT1 INPUT vt INPUT2 INPUT 2 OUTPUT 2 OUTPUT OUTPUT I v INPUT 1 ANPUT 1 INPUT 2 INPUT 2 Fig 53 Connexion diagrams of the LM324 left and the LM339 right Fig 54 Pictures of the populated cell voltage measuring circuit Remark For the tests of the circuit a third version isn t realised and the circuit shown in figure 52 and 54 respectively is used The PCB layout on Opuser has been adapted 5 1 2 Current measuring circuit Unfortunately I didn t found the ti
61. d to the uP So the uP knows that he has to begin to monitor the current and can decide what to do For example it can stop some motors or other parts of the rover system to determine the error source or disconnect the batteries from the load charger Moreover the monitoring allows having knowledge about how the current increases Anyway it needs a current measure to allow controlling the current The surveillance of the current value can only be taken over by the microprocessor But then it has to be done permanently and no uP independent security is existent to protect the batteries and the chargers The possible security measures are described later in chapter 4 5 2 In order to protect the batteries the discharge current is limited to 10A and to protect the charging unit 1210i the highest allowed charge current is 7 7A For protecting the different electronic circuits appropriate fuses are deployed As mentioned in chapter 3 3 3 the current measure is done with a current sensor from the company LEM It has the advantages not to influence the measured current to provide an easily measurable signal and that the measuring accuracy is very high 0 2 Such sensors are not available in Akihabara and therefore they have to be ordered from companies that sell LEM components But there they are quite expensive 3500 Therefore Prof Kunii proposed using shunt resistances and hence this approach is also analysed chapter 4 5 3 But suggest us
62. e are the same as for the circuit shown in figure 18 For the signal uP1 the microprocessor has to provide a low signal OV in order that the battery unit is connected to the load and a high signal 5V for allowing its charge The signal uP2 is set to 0 due to the inverter the signal for R is high The inverter is only there to ensure that in case that the uP should be defective and delivers a low signal the input R is high nevertheless In case of an error S goes low and thus the output Q of the RS latch gets high As long as Q is high only the charge of the batteries is possible The state of uP1 has no influence The microprocessor has to give a high signal on uP2 in order that Q gets low and that the signal uP1 gets active again The following truth table resumes the effect of the different signals Error NoError 1 110 Loto tr discharge Fig 41 Truth table switching through analogue circuit independent of the microprocessor Biner Dominik Diploma thesis page 54 78 ooo Power supply and motion system for planetary rover NALAIS a Hes so wiis cp m pas Tokyo February 20 2008 jaliste SS 7 K F Chuo University Remark As the case R 1 and S 1 uP2 0 and S 1 don t change the state of the RS latch s output Q at power up the microprocessor has to provide a high signal on uP2 to ensure that the output Q gets low As defined in chapter 4 4 3 1 the integrated circu
63. e and appropriate condition 3 For contact information concerning the HMSL and JAXA see chapter 9 2 The references used for writing this paragraph are listed in chapter 9 1 2 Structure of this diploma work 2 1 Introduction to my work The development of the power supply for the new type of planetary rover M6 is my main work here in Japan Chuo University Korakuen Campus This work is linked to the speed regulation of the motors used for the motion control of the rover On this account also help to develop a method for realising the speed regulation Besides depending on the available time help Dr Eng Kojiro lizuka with the optimisation of the wheel s shape As mentioned before the development of the solar cells isn t done by Chuo University In the first instance my work consists of setting up concepts and to define possible approaches The final realisation of the circuits has to be done by a laboratory with the appropriate infrastructure JAXA Japan Aerospace Exploration Agency Biner Dominik Diploma thesis page 6 78 ooo Power supply and motion system for planetary rover M NALAIS Hes so wiis tp m pas Tokyo February 20 2008 Chuo University 2 2 Requirements specification 2 2 1 Power supply As aforementioned the necessary electrical power has to be delivered by lithium polymer battery cells LiPos Following conditions have to be kept Capability to deliver
64. e as soon as the gate source voltage Ucs reaches the threshold voltage Urn and the transistor enters the active zone the capacity Ces is increased dynamically by the Miller effect Especially when Ucs reaches the same value as the drain source voltage Ups the capacity is maximal and Ugg flattens But at this point the MOSFET is already nearly fully switched on Therefore the drive resistance Reate should be small and the gate current high in order to allow a fast charge and discharge of the gate capacities To minimise the losses due to the Biner Dominik Diploma thesis page 20 78 ooo Power supply and motion system for planetary rover 7 7 NALAIS i Hes so wanie ch Tokyo February 20 2008 o SPRAY Chuo University switching the commutation has to be done as fast as possible But to switch to fast could introduce some EMC electromagnetic compatibility problems therefore in general a small drive resistance is put in series to the gate The switching of the transistors is realised by MOSFET drivers available on the market For example the company IRF is producing such drivers As mentioned before as longer the switching time as higher are the losses due to the switching Therefore the current given by the driver have to be high enough and his internal resistance small enough The required gate voltage for the upper transistors S1 and S3 depends of the voltage of the source because their source is not conn
65. e between the different cell voltage levels 3 0V 3 2V etc is bigger and therefore the accuracy higher Such as for the amplifier as comparator the LM339 is deployed for making the first tests DIP component like the LM324 The datasheet of the LM339 is on the enclosed CD as well appendix 5i SMD Surface Mount Device These components are mounted directly onto the surface of printed circuit boards PCBs and are much smaller and lighter than DIP components DIP Dual In line Package also called DIL Biner Dominik Diploma thesis page 26 78 ooo Power supply and motion system for planetary rover M H es s OU WALLIS gt p Jh X Ea Tokyo February 20 2008 IN Chuo University With this circuit the input voltage U is calculated as follows The equivalent scheme to determine this voltage is shown below in figure 12 _ R R R _ R 5 em Uns U i R R R R R R R R R R R R R R R R R R _R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R U U y U 9 U R R R R R R R R gt U U R R R R R R R U1 U1 Ri Ri R3 eo R5 Fig 12 Equivalent scheme of the modified amplifier for calculating the input voltage of the OP amp Now the gain of the modified amplifier fig 11 has to be calculated U U U G with G gai
66. e voltage source V2 right scheme of fig 35 It provides a rectangular signal with amplitude 2V and an offset of 2 5V The frequency is set to 20kHz most likely the frequency of the PWM signal and the duty cycle to 70 Therewith the signal is at 4 5V during 70 of the period 35us and at 0 5V during the remaining 30 Thus the voltage after the filter has to be 0 7 4 5V 0 3 0 5V 3 3V Biner Dominik Diploma thesis page 52 78 ooo Power supply and motion system for planetary rover AI NALAIS Hes so wais C tp m x By Tokyo February 20 2008 Chuo University Probe Cursor A1 106 362m 3 2956 a2 130 425m 3 3006 dif 30 123n 4 9560n 50ms 100ms 150ms 200ms 250ms 300ms a V UOUT Time Fig 37 Simulation result of the battery current measuring circuit with current sensor LEM As it can be seen the voltage is 3 3V as wished The time constant of the RC element is t R C 15ms and hence it needs some time until the voltage over the capacitor reach its final value 100ms If this time has to be reduced in order that the current measuring circuit reacts faster to changes of the current value a smaller capacitance resistance has to be deployed This means that the cut off frequency has to be increased 4 5 2 Security measures uP independent 4 5 2 1 Too high current during the discharge process
67. easured with a shunt resistance A D converter 63 Fig 51 Picture of the first version of the cell voltage measuring circuit PCB 66 Fig 52 Picture of the second version of the cell voltage measuring circuit PCB 66 Fig 53 Connexion diagrams of the LM324 left and the LM339 right 67 Fig 54 Pictures of the populated cell voltage measuring circuit 67 Fig 55 Pictures of the test setup for the cell voltage measuring circuit 68 Biner Dominik Diploma thesis page 4 78 ooo Power supply and motion system for planetary rover DN H es s O WALLI gt p Jh Je Ea Tokyo February 20 2008 IN Chuo University List of appendices The appendices are placed at the end of this report All the datasheets of electronic devices are available as PDF files on the enclosed CD appendix 5 1 Study results about the wheel form done by Kojiro lizuka Yoshinori Sato Yoji Kuroda and Takashi Kubota 1a and 1b Extract from the Hyperion product catalogue List of material bought for making the first battery charge discharge tests Test record of the cell voltage measuring circuit a A O PP CD with the datasheets of electronic devices 5a 12V DC motor from Maxon A max 26 with gear amp encoder 12V DC motor from Maxon A max 19 with gear amp encoder Charging unit 1210i from Hyperion user manual 5d Balancer LBA10 from Hyperion user manual MOSFET transistor K2936 5f Operational amplifier
68. ected to ground and thus not on a OV potential Thus the driving circuit for these transistors have to be related to the source this means the driving circuit follows the source voltage The picture below shows the simplified scheme of such a driving circuit Fig 9 Simplified scheme of a MOSFET driving circuit The capacitor C1 is charged when M2 is closed bootstrap circuit This capacitor provides the necessary energy for the switching of M1 Therefore always the lower transistors S2 or S4 in figure 8 have to be turned on at first The gate source voltage of the upper MOSFET is exclusively determined by the supply voltage of the driver in this case 15V The source potential of M1 is irrelevant Of course the signal for driving M1 has to be provided by a level shifter circuit Such circuits use charge pumps to create a higher voltage as the supply voltage which is necessary for switching the upper MOSFETs A level shifter circuit is already implemented in common driving circuits e g drivers from IRF Moreover many MOSFET drivers have an undervoltage protection also called undervoltage lockout protection UVLO This protects the application in the event of a low supply voltage by switching off the MOSFET transistors For contact information of the company IRF as well as links to general information about MOSFET transistors and their switching see chapter 9 6 The motors used for the steering of the motor have to stand still most of
69. ed before for making the first tests the LM324 is deployed So at first the calculation of the resistance values for this case is done The maximal input common mode voltage is 3V and hence the voltage U is set to 3V The maximal output voltage is also 3V and the highest cell voltage to be measured is 4 4V Therefore the gain has to be at most ga ta V 0 68 U 44V In The gain G is set to 0 6 so that the output voltage is 2 64V for a differential input voltage of 4 4V With the minimum cell voltage of 3 0V the output voltage is 1 8V The highest possible voltage for U is 8 times the cell voltage measure of top cell s voltage This means Uimax 8 4 4V 35 2V Now the value of the resistance R can be calculated by setting the value of R4 Biner Dominik Diploma thesis page 29 78 ooo Power supply and motion system for planetary rover M H es s O ren C p Jt k Ea Tokyo February 20 2008 IN Chuo University R U VE N eay u m R R i G B R gt R B R A B R R 1 1 A B R R R l R ES 27 Dr Ged S B U G The values of the resistances are chosen from the series E24 If possible the values are chosen from the series E12 because most of these values are already available in the laboratory R is set to 68kQ R R _ U 3V U 35 V G 0 6 an U G P R 68kQ gt R 7 5kQ El2 R 6 8kQ R gt U al 2 1V Sa
70. efined in chapter 3 3 6 the relays used to switch between the charge and the discharge of the batteries are driven with bipolar transistors Thus for stopping the discharge cell voltage at 3 0V this transistor can be actuated in order that the batteries are switched into the charge position The batteries are connected to the balancers when the relay is in rest position hence when the transistor is switched off So in case that the transistor should be defective the batteries are not discharged The schema of the driving circuit for the relays used for switching between the charge and the discharge of the batteries is the following side signal from uP 2 microprocessor signal from gt 1 2 an analogue circuit Fig 18 Driving circuit for the relays used for switching between the charge and the discharge of the batteries switching through analogue circuit possible independent of the microprocessor With this circuit the microprocessor has to provide a low signal OV in order that the batteries are connected to the load and a high signal 5V for allowing their charge an uP discharge NoError 0 a 0 Error ge 0 gt charge Ucen lt 2 8V 0 Fig 19 Truth table switching through analogue circuit independent of the microprocessor Remark As aforementioned the analogue circuit affords OV in case of an error This has the advantage that only in that case the comparator s output draws a current open c
71. es of the test setup for the cell voltage measuring circuit 7 Conclusion 7 1 Work performed My work consisted of setting up concepts and defining different possible approaches e A suggestion for a new wheel placement of the rover has been given e A circuit for realising the motor speed regulation has been proposed and partly dimensioned Biner Dominik Diploma thesis page 68 78 Power supply and motion system for planetary rover M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University It has been defined how to compose the complete power supply The concepts for controlling the voltage of each battery cell as well as the battery current have been set up The circuits concerning these surveillances have been dimensioned in part different approaches o A test circuit of the cell voltage measuring circuit has been built and tested Concerning the surveillance of the battery s temperature the concept has been set up But this control has not been realised yet 7 2 Work to be undertaken future tasks The available time was too short for finishing developing the complete power supply including all the security measures Moreover the Japanese lessons during the first 13 weeks took up much time For most parts only realisation suggestions have been established and in part different approaches have been defined due to the infrastructure and missing informatio
72. g between the charge and the discharge of the batteries switching through analogue circuits possible uP independent faulty 53 Biner Dominik Diploma thesis page 3 78 Power supply and motion system for planetary rover H es s O N WALLIS gt p w Je Ea Tokyo February 20 2008 Chuo University Fig 39 Truth table of the RS latch M74HC279 54 Fig 40 Driving circuit for the relays used for switching between the charge and the discharge of the batteries switching through analogue circuits possible uP independent final version 54 Fig 41 Truth table switching through analogue circuit independent of the microprocessor 54 Fig 42 Differential amplifier with low pass RC filter 57 Fig 43 Electrical schema of the battery current measuring circuit with shunt and LM324 58 Fig 44 Electrical schema of the battery current measuring circuit with shunt and rail to rail amplifier _ 59 Fig 45 Simulation schema of the battery current measuring circuit with shunt and LM324 60 Fig 46 Simulation result of the battery current measuring circuit with shunt and LM324 60 Fig 47 Differential amplifier with low pass RC filter 61 Fig 48 Simulation schema of the battery current measuring circuit with shunt and LM324 62 Fig 49 Simulation result of the battery current measuring circuit with shunt and LM324 63 Fig 50 Used control byte for the conversion of the current value m
73. g others there was almost no stock of electrical components no software to simulate electric circuits and only few power sources and measuring equipment e g no possibility to measure temperature and no current measure with oscilloscope possible didn t get a PC to work on and therefore had to use my own portable PC on which no programs were installed could use for this work Fortunately got the simulation software OrCAD from my person in charge in Switzerland But due to the Windows version on my portable PC Vista many compatibility problems occurred with the program and it took some time to make it work properly Moreover the software is not as sophisticated as it is in my laboratory in Switzerland e g libraries Furthermore couldn t speak Japanese properly especially technical language and the students of my laboratory didn t speak English that well Therefore there were many communication problems and the research of components was very difficult All components were bought at Akihabara name of a town in different shops Their internet sites were only in Japanese and their staffs only spoke Japanese didn t find many components decided to deploy and hence wasted much time with the search of components and with reading datasheets The library of Chuo University had no books in English could use for my research and thus the only source of information was the internet Anyway all laboratory mates were very cooperative
74. ged In this context the regulation of this battery voltage has to be realised Moreover a method for charging it has to be developed and finally the concept for the switching of the battery has to be set up connection and disconnection of the battery from the load charger See chapter 4 7 Biner Dominik Diploma thesis page 70 78 ooo Power supply and motion system for planetary rover M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University e Realisation of the circuit for the motor speed regulation by Shimanuki Toru See chapter 3 4 e Test of the effectiveness of the proposed wheel placement See chapter 3 2 Due to lack of time the aspect of the behaviour of the electrical components under space conditions has not been treated during this diploma work It has to be done by the next student Or by JAXA or other institutions which already have experience in this domain But as the choice of components is clearly defined in case of necessary adaptations the required specifications are well known 7 3 Major difficulties encountered during this diploma work The following description of problems is personal and concerns my exchange in Japan The major difficulties were that the laboratory was badly equipped for the work had to do and particularly that didn t have any expert person in my field on site It s an informatics laboratory and not a power electronics lab Amon
75. ged a voltage measure is necessary As soon as the voltage of one cell reaches 3 0V to 3 2V it means that the battery is empty The voltage value is depending on how much current is drawn from the battery see fig 4 There are different ways for measuring this voltage depending on how the packs in series or parallel are discharged If the voltage of each cell decreases at the same level it s sufficient to measure the voltage of one battery pack or even of one battery unit Else it s necessary to control the voltage of each cell To get the cell s voltage either the signals on the balance harnesses of the balancer are used or a cell voltage measuring system has to be installed Action done Connect other two units to the consumer depending on their charge level Interrupt existent connexion to the load Supply the appropriate chargers and balancers and connect them with the empty units 2 end of charge The detection of the end of charge Usei 4 2V is done automatically by the charger The balancer is shut down but as abovementioned it has to be disconnected from the batteries This point will be detected by a measure of the current drawn from the batteries by the balancer which at this time is only about 0 5mA The connexion to the load is done when the other two units are dis charged Action done Take away the power supply of the appropriate chargers and balancers At any time the temperature as well
76. h Je Ea Tokyo February 20 2008 IN Chuo University To determine the wattage of the resistances the voltage over them is calculated For the resistance Ra of the modified differential amplifier the necessary formulas have already been developed before while calculating the gain a Ra U U R R R 2up R2UP nax Lmax R R R R R R R U 8 U iia 35 2V 2 gt U 4 03V gt P U konpas 2 4mW R2UP max ui R2upmax R _L 2 R R R R R b Ry row U kaow a U bi 2 3 a i gt U u R R R R R R R i R R R R R R Uy 7 U on 30 8V U oua 4 6V U ies gt U or 3 53V gt Perrot R 1 83mW Remark Of course the calculation for the upper resistances on the positive input of the amplifier would be sufficient because the voltages and therefore the power dissipations of the lower ones are smaller But to prove this the calculation is done nevertheless For the determination of the wattage of the resistances R R3 and R the equivalent schemes showed in figures 12 and 13 are deployed la R Fig l2 gt Ua U Ukru Cy 8 U Ly 35 2V U Dass Bass 20 67mW m 1 Ib Row Fig 13 gt U kiiow f U Un f U 7 U 4 30 8V U gt Daa N Bosse a 15 83mW 1 Biner Dominik Diploma thesis page 34 78 ooo Power supply and motion system for planetary rover H es s O N WALLIS gt
77. h corresponds to the desired gain of 25 The cut off frequency of the filter at 3dB thus 24 95dB is at 9 7Hz see upper Probe Cursor window After that as we have a first order filter the slope is about 20dB per decade see lower Probe Cursor window 4 5 3 3 A D conversion with the MAX197 The signal delivered by the rail to rail amplifier is between 4 5V and 4 5V Thus the input voltage range of the A D converter has to chosen from 5V to 5V As shown in chapter 4 4 4 1 fig 23 the choice is done by setting the bits D3 and D4 of the control byte BIP and RNG In order to get a range of 5V to 5V BIP is set to 1 and RNG to 0 Due to the change of the two bits BIP and RNG the control byte for this case is the following D D D5 m D3 m DM Do PD1 PDO AcamoD RNG BP a2 a1 AO EEE Ee Ee Se GET eS RE e E Fig 50 Used control byte for the conversion of the current value measured with a shunt resistance A D converter Remark The A s for the bits AO to AT stand for the address used to choose the analogue input channel as shown in the table on figure 22 Everything else stays unchanged and the converter is used as described in chapter 4 4 4 1 4 5 4 Comparison between the different measuring methods The current measure with the shunt resistance is much more delicate and it needs an additional supply voltage of 5Vdc to be able to measure a negative current current flowing into
78. he temperature can be surveyed by it too in order to be independent of the charger Moreover same as for the battery current and cell voltage control uP independent securities can be installed This means that the voltage given by the temperature sensor is compared to a reference value by means of analogue circuits In case that a critical value is reached the batteries are directly disconnected from the load charger without the need of an order from the microprocessor Finally especially depending on how good the temperature conduction between the batteries and the sensor is it has to be decided if it s necessary to use a better sensor For example the LM35A which has a typical accuracy of 0 2 C 1 C at most 4 7 Additional battery As mentioned in chapter 4 4 2 an additional battery is necessary in case that the four battery units have to be charged This battery has to assure that the microprocessors the measuring circuits as well as the motors used to move or to extend the solar cells are supplied while the other batteries are charged For the processors and the measuring circuits a 2 cell lithium polymer battery is sufficient for delivering the required 5V But depending on the voltage needed for the motors to move or to extend the solar panels more cells are necessary As the deployed motors are not chosen yet the choice of this battery isn t done now The capacity of the battery has to be adapted to the consumption of these
79. ing a LEM sensor because of the aforementioned advantages Moreover the measure with a shunt resistor is much more delicate 4 5 1 Current measure with current sensor from LEM The current sensor LTSR 6 NP is deployed It can be single supplied with 5Vdc and with it a current up to 19 2A can be measured It delivers a voltage value and the relation between the output voltage Uout and the measured current Ip is as follows Vor V I A 0 Pmax PN Pmax Fig 32 Linear relation between the output voltage and the measured current LEM LTSR 6 NP As it can be seen the relation is linear and expressed with the following formula U out ref I U y 0 625V with U 2 5V P nom By changing the connexion scheme the nominal current Ipnom can be chosen Biner Dominik Diploma thesis page 47 78 ooo Power supply and motion system for planetary rover VALAIS H e S S o WALLIS C puk ay Tokyo February 20 2008 Pr en Chuo University Number Primary nominal Nominal Primary Primary Recommended of primary current rms output voltage a insertion inductance connections 2 5 0 625 2 5 0 625 2 5 0 625 Fig 33 Choice of nominal current through different connexion schemes LEM LTSR 6 NP As seen in figure 32 the maximum output voltage is 4 5V and therewith the measureable current range can be calculated U ar U yep 0 625 Loms 4 5V U nos
80. it M74HCO2 is used to realise the NOR gate The inverter is also realised with a NOR gate see fig 20 As AND gate the MM74HC08 is deployed Such as the M74HC02 it works with a supply voltage of 5Vdc and is available in space saving SMD package The datasheet of the MM74HC08 is also available on the enclosed CD appendix 5p 4 5 2 2 Too high current during the charge process Concerning the charge current the charger 1210i is not protected against a short circuit of its output Therefore it s needed to identify when the current reaches a critical value In that case the supply voltage of the appropriate charger is taken away directly by analogue circuits Due to the power limitation of the charger of 180W the maximal delivered current is 7 5A when the batteries are empty Ucell 3 0V Thus as soon as the current reaches 7 7A the chargers are shut down The principle is exactly the same as for the double security against a too high cell voltage described in chapter 4 4 3 2 The signal provided by the comparators see fig 34 is used to switch off the transistor in order that the chargers are no longer supplied As mentioned in chapter 4 4 3 2 the choice of the MOSFET transistor has not been done yet and therefore the circuit for driving them is not realised at this point But the principle is the same as for the protection against a too high current during the discharge described previously 4 5 3 Current measure with shunt resistance
81. ital data I O port is configured to operate with 8 bit data buses Hereinafter the function of each pin is specified and therewith also the functionality of the device Afterwards the necessary actions to start and read a conversion are described 4 4 4 1 1 Pin description To allow a better explanation of the device here a picture of the converter in its simplest operational configuration 5V ra 2 T Tao T alter ae uP jJ 4 WR JF N 4 7uF CONTROLS _ ds sais a INPUTS ANALOG INPUTS D3 D11 4 D2 D10 D1 D9 DO D8 ee uP DATA BUS Fig 21 Picture of the A D converter MAX197 in its simplest operational configuration On the right side you can see the 8 analogue inputs CHO to CH7 To choose which input is active the corresponding address has to be given on AO to A1 the 3 LSBs of the control 7 LSB Least Significant Bit It s the bit in a binary number having the lowest value in general rightmost of the number Biner Dominik Diploma thesis page 41 78 ooo Power supply and motion system for planetary rover y NALAIS H e S S o WALLIS C tp m x ea Tokyo February 20 2008 achi er Chuo University byte DO to nn The format of the Er control a is shown on page 45 il i Fig 22 Table for the selection of the analogue input channel A D converter The input voltage range of the analogue inputs can be chosen by setting the bits D3 and D4
82. ith a rail to rail amplifier the gain is set to 45 Uout max 4 5V Capacitors are used to create a low pass filter in order to get the average value and that the noise on the current signal is shortened to ground and therefore not amplified As the aim is to measure a DC current the cut off frequency of the filter is set to 10Hz Thus the differential amplifier circuit is the following Biner Dominik Diploma thesis page 56 78 ooo Power supply and motion system for planetary rover NN H es s O WALLI en Jh X Ea Tokyo February 20 2008 IN Chuo University R a R U U U with Gain G R R R R Fig 42 Differential amplifier with low pass RC filter First the determination of the resistance values For the LM324 G 25 with a value of 30kQ for R Rz the highest accuracy is reached With a gain of 45 rail to rail amplifier a value of 15kQ brings out the best R 1 ar z 25 gt R G R R 1 2 R R 30kQ gt R R 15kQ R 750kQ R gt G pa gt 25 R R R 2 G 45 gt R G R R R R R R 15kKQ gt R R 7 5kQ R 675kQ E12 R 680kKQ R Goal f R R Remark The values of the resistances are chosen so high in order that the necessary capacitance for realising the RC low pass filter doesn t become too big Now the capacitor s value is calculated Due to the virtual ground on the ent
83. lems which can occur while driving on planetary surfaces such as slipping of wheels which induces additional errors to the position information of the rover or worst if the rover gets stuck Some studies done before by the Chuo University in Tokyo show that especially if the rover has to overcome rough terrain and slopes the shape of the wheels has much influence on the rover s mobility Also the weight of the rover has to be as low as possible to decrease costs and the probability of getting stuck An actively articulated suspension is essential because it can greatly improve the rover s stability in rough terrain 1 3 At the moment the Human Machine Systems Laboratory HMSL at Chuo University in Tokyo is developing a new rover type called M6 It will be used to explore the poles of the moon For the M6 the complete system has to be composed including a battery with a power source for charging it Only the mechanical design is done by other institutions The power supply is realised with lithium polymer batteries and solar cells The development of the solar cells is carried out by JAXA Lithium polymer batteries are quite sensitive to temperature and over or undervoltage Furthermore the balance between the different cells has to be granted in order to guaranty a good battery performance and a long battery life This means that after charging all cells have to be at the same voltage Thus it needs provisions for keeping them in a saf
84. lly open contact and one normally closed contact with a common terminal PWM Pulse Width Modulation A PWM signal represent a rectangular signal where the duty cycle is changed like needed With an H bridge used like described above with a duty cycle of 50 thus a normal rectangular signal the motor stands still With 50 to 100 the speed increases in one direction with 50 to 0 in the other direction gt Biner Dominik Diploma thesis page 18 78 ooo Power supply and motion system for planetary rover M H es s O ren C p Jt k Ea Tokyo February 20 2008 IN Chuo University The duty cycle is calculated as follows U ncmoror U tan 2m 1 m duty cycle T period of PWM signal T Tp gt m U int Dr ZU forward la Ojon 24V U bemor 12V gt m 0 75 1b U yon 33 6V3 U benor 12V gt m 0 68 backward 2a Upan 24V3 U pemotor 12V gt m 0 25 2b Ua 33 6V3 U pemo 72V gt m 0 32 Remark As it can be seen for moving forward the duty cycle changes only between 50 stand still and 75 full speed And thus for the other direction of rotation it changes only between 50 and 25 This is true for the case that T Tons Tons3 this means that the PWM signal is applied as shown in the figure below fig 8 The necessary duty cycle to reach the desired motor speed is determined by measuring the motor speed Ubatt Fig 8 Electrical scheme of an H bridge
85. me for manufacturing the PCB with the current measuring circuit For the tests the circuit using the current sensor from the company LEM would have been realised see fig 34 Biner Dominik Diploma thesis page 67 78 Power supply and motion system for planetary rover Hess Haute Ecole Specia de Suisse occide VALAIS th o WALLIS ch Tokyo February 20 2008 SPRAF o n Chuo University niversity of Ap d Sciences Western Switzerland 6 Test of the electronic circuits PCB 6 1 1 Cell voltage measuring circuit The cell voltage measuring circuit has been tested and works as desired The test record with all the conducted measures is shown on appendix 4 But as it can be seen on appendix 4 the amplification of one differential amplifier is 0 665 instead of 0 6 This corresponds to a relative error of 10 8 which is inadmissible For example for the detection of the too low cell voltage of 3 0V the reference voltage is set to 3 0 6V 1 8V and with a gain of 0 665 the effective cell voltage value is 1 8V 0 665 2 7V To solve this problem either resistances with a smaller tolerance have to be used or the resistances R see fig 11 have to be replaced by potentiometers in order that the gain can be adjusted manually But in the latter case the adaption of the gain is delicate because two potentiometers have to be regulated at the same time Fig 55 Pictur
86. n As seen for the amplifier of figure 10 the gain is R4 R3 But in this case U and U of that formula are the voltages over the resistances R3 Roup is the upper resistance and Raw the lower one therefore U and U of the formula for the amplifier of figure 10 are now UrRoup and Urziow R gt U su U R2up U kalow R Ur2up equals to the voltage Urs that has been calculated before R R R R gt Up Ur U U i l z R R R R R R R R R Biner Dominik Diploma thesis page 27 78 ooo Power supply and motion system for planetary rover DN H es s O WALLIS gt en Jh Je Ea Tokyo February 20 2008 IN Chuo University To calculate the voltage Urz2ow a Superposition is necessary The equivalent scheme to determine this voltage is the following U2 Uout Fig 13 Equivalent scheme of the modified amplifier for calculating the voltage Urzow So for the voltage over the resistance Row we obtain D U 0V R U with R R2low R R R R R R R R R R R R R R R R R R gt U gt U pote U 2 U 0V RR R R gt U porto U u o R R 2 R R R R gt U U Lo R2low out R R R R R i R R R R R R U eee ee a R R R R R R R R R R R R R R2low U katom U kaiow U i Now the gain can be calculated
87. n The final choice has still to be made and some parts have still to be dimensioned My goal was to come along with the work as far as possible and in order to give a good overview define as clearly as possible the work that still has to be done To do so the following points resume the future tasks Choice of an appropriate DC DC converter or converter modules for the regulation of the solar cell s voltage generation of the supply voltage for the chargers In this context the 2 or 4 MOSFET transistors for connecting disconnecting the chargers power supply have to be chosen as well See chapter 4 2 DC DC converter and 3 3 6 MOSFETs As the MOSFETs mentioned above have not been chosen yet their driving circuit has to be developed In this regard it has to be decided if the wP independent security measures are installed or not The circuit for realising these security measures for the discharge process has been dimensioned switching of the bipolar transistors used to drive the relay s coils change between charge and discharge position of the batteries But the one for the charging operation has to be developed switching of the MOSFETs for connecting and disconnecting the charger s power supply See chapter 4 4 3 and 4 5 2 In case that the relay from the company Finder isn t procurable appropriate relays for switching between the charge and the discharge have to be chosen See chapter 4 4 3 1 page 39
88. n of the circuit for the motor speed regulation chapter 3 4 is taken over by other persons Therefore is this section only the realisation of the power supply is treated 4 2 Regulation of the solar cells voltage The power for charging the batteries is given by solar cells For charging all the batteries at the same time with a current of 1C totally 600 watts are required Each charger can deliver up to 180 watts and therefore the maximal power is 720 watts The supply voltage of the chargers has to be between 12Vdc and 15Vdc Therefore it needs a powerful voltage regulation to generate this voltage This is realised with a DC DC converter from the companies Lambda or Vicor for contact information of these companies see chapter 9 4 Because the solar cells are not finished developed now the choice of an appropriate DC DC converter isn t done yet For reaching the demanded power of 600W it s also possible to use multiple converter modules in parallel To fully profit of the efficiency of the converter the converter has to be used as near as possible at his maximum power Therefore the use of modules instead of one DC DC converter could be advantageous connect only as much modules as necessary 4 3 Voltage levels generation The battery voltage is between 24Vdc and 33 6Vdc depending of the battery s charge state For supplying the ultrasonic motors used for moving the camera mast a stable voltage of 24Vdc is needed The Maxon
89. nge and have broadened my horizon They gave me the chance to get in contact with new people to discover a new culture and an interesting country Moreover it allowed me to improve my English skills as wrote the report in English hope that it will always be possible for students to do such exchanges in order to show them new fields in science and different working methods as well as open their mind for other countries and cultures Moreover it s an excellent opportunity to make new acquaintances around the world 8 Acknowledgements want to thank the HES SO and its international centre MOVE which allowed me to make this exchange Furthermore thank all the people from the Kunii Laboratory Human Machine Systems Laboratory HMSL Faculty of Science and Engineering at Chuo University Tokyo who were very friendly and welcomed me with open arms Special thanks to Mr Masahiko Suzuki from the HMSL for his great efforts to speak English and for his support during my work Mr Shunsuke Amagai from the Robot Engineering Laboratory who spoke very good English and helped me a lot with my daily life in Japan Ms Watanabe Yumiko from the international centre of Chuo University for the administrative support My family and my friends especially my mother Ruth Biner for the great moral support during my whole stay in Japan Professor Michel Imhasly from the HES SO for the administrative support Professor Hans Peter Biner
90. nn R R G real Remark The value of 7 5k2 is contained in the series E24 But therewith through calcu lation the voltage U will be exactly at the maximal value of 3V Therefore for R2 a value of 6 8kQ is chosen which is available in the laboratory For the resistances R3 and Ry the choice of R3 6 2kQ brings out the best B R R s g _ G R R R R R R R R R R R R R 2 R 6 2kQ gt R 81 72kQ E24 R 82kQ FR R R R R R R R R 0 602 The first cell can be measured with a standard differential amplifier see fig 10 because the voltage U is low enough Biner Dominik Diploma thesis page 30 78 ooo Power supply and motion system for planetary rover He S soW WALLIS gt puk Ea Tokyo February 20 2008 Chuo University rock sity For reaching a gain of 0 6 the best values for the resistances R and R2 of figure 10 are the following R 30kQ gt R 18kQ Nn gt Ga 0 4 Remark The use of a non inverting amplifier is not possible because the input common mode voltage would be too high So the circuit for measuring the cell voltages with the LM324 is as follows 5Vdc A 10k 3 7Vdc cell8 A AMV 6 OV gt cell voltage too low 68k 6 2k 6 8k 6 8k 82k 5Vdc AN 5 3 7Vde cell7 6 8k 82k 5Vdc gt 3 7Vdo
91. nnel Therefore it depends on the dead time As the dead time is awaited before closing S2 and S3 and again before closing ST and S4 after reopening S2 and S3 the time T ors is about two times the dead time To 2 taeaa Biner Dominik Diploma thesis page 22 78 Power supply and motion system for planetary rover M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University The calculation of the losses during the switching process is more difficult One part is formed by the losses due to the channel of the MOSFET Because to fully open the channel takes some time and during this time the drain source voltage falls down to the saturation voltage and the drain current increases to its final value The losses are calculated by multiplying the drain voltage Vps with the drain current Ip But because it s a dynamic event to get the amount of wasted energy during one switching operation an integration of this multiplication is necessary Therefore we need to know the wave form of these two values while switching The same phenomenon occurs while switching off only that the current decreases and the drain source voltage increases The other part is the necessary driving power For a complete switching process the total gate charge has to be delivered by the driving circuits Thus by means of the total gate charge Qa that is also used to calculate the switching time in function of the drive curren
92. nsor only the 24 of March and didn t have time to analyse the use of it It s the LM35DZ and it provides an output voltage linearly proportional to the temperature in degree Celsius The measuring error is 2 C at most Its datasheet is also available on the enclosed CD appendix 5q It still has to be defined how the sensor is mounted on the battery packs to get an efficient and reliable temperature measure the time constant of the sensor in still air is about 16s Especially it needs a good temperature conduction between the batteries and the sensor For the temperature control during the discharge the same sensor can be used to transmit the value to the microprocessor In this case the supply of the sensor has to be done by the 5Vdc regulator instead of by the charger The voltage provided by the sensor is relayed to an A D converter in order to be readable by the uP The necessary actions in case of a critical temperature value have to be decided As the use of a cooling fan is not possible in space most likely the motors will be stopped as they represent the biggest consumer or the batteries will completely be disconnected from the load Biner Dominik Diploma thesis page 64 78 ooo Power supply and motion system for planetary rover M NALAIS Hes so wiis cp m pas Tokyo February 20 2008 Chuo University As the value of the temperature is transmitted to the microprocessor during the charge t
93. of the control byte BIP and RNG In our case they are both set to 0 to get a range of OV to 5V el oo Fig 23 Table for the selection of the voltage range of the analogue inputs A D converter The reference voltage on pin 26 REF can either be provided internally by the device itself or given externally This voltage determines the full scale input voltage RANGE ZERO SCALE V SCALE FULL SCALE te N Fig 24 Table for the determination of the full scale input voltage A D converter In internal reference mode the device provides 4 096V on this pin and therefore at a voltage of 4 096V 1 2207 5V the digital value is at his maximum all 12 bits set to 1 The pin 25 REFADJ serves to externally change the reference voltage Vrer 1 6384 Vrerans The desired reference voltage can also be directly given externally on the REF pin and in that case the entrance REFADJ has to be connected to the power supply Vpp like showed in figure 21 In every case the reference Vrer has to be between 2 4V and 4 18V If an adjustment of the full scale input voltage is done depends on the maximum voltage given from the battery cell voltage measuring circuit As mentioned in chapter 4 4 1 the LMV324 is deployed for this measure maximum output voltage of 4 4V Therefore the converter is used in internal reference mode because the full range of 5V corresponds to 2 1 4095 and 4 4V is already equivalent to a digital value of 3 60
94. ollector output and it allows a wired and connexion The NOR gate shown in figure 18 drives two bipolar transistors instead of one as shown because each battery unit has two relays for switching between the charge and the discharge see fig 7 Thus the basis current of the transistors has to be less than half of the maximal output current of the NOR gate Biner Dominik Diploma thesis page 38 78 ooo Power supply and motion system for planetary rover M VALAIS Hes so wai cp Tokyo February 20 2008 o SPRAY Chuo University As NOR gate the integrated circuit M74HCO2 is deployed It works with a supply voltage of 5Vdc and is available in space saving SMD package It can deliver up to 25mA which is enough for driving the bipolar transistors For more information about the M74HCO2 see the datasheet on the enclosed CD appendix 5j The inverter is also realised with a NOR gate ini N in int in2 out I 0 0 0 1 er 1 1 110 Fig 20 NOT gate realised with a NOR gate In order that it doesn t need an additional voltage level 24Vdc relays are deployed A relay from the company Finder series 66 is used because at a voltage of 30Vdc it can switch a current up to 25A But couldn t get this type and therefore for the tests a relay from Omron LY2 is deployed available in Akihabara But the LY2 can only switch up to 10A at 24Vdc with resistive load and
95. only up to 5A if the load is inductive Both types are DPDT For more detailed information about the relays see the datasheets on the enclosed CD appendices 5k amp 5l The current necessary for driving the coil with 24Vdc is 70 6mA for the type from Finder and 36 9mA for the one from Omron Thus the power consumption of the relay from Omron is only about half as much as the one of the other relay U a 24V 1 Finder Loa 70 6mA gt Py lea Uou 1 694W 2 Omron I 36 9mMA gt Poli U ou 0 886W For both types the bipolar transistor C945 existent in the laboratory is deployed to drive the relay s coil It is very small and can drive a collector current up to 100mA and withstands a collector emitter voltage up to 50V The collector emitter saturation voltage is only 0 3V at most and therefore the losses and hence the heating of the device is low Ua 0 3V amp 250 CE sat th JA 1 Finder le 70 6mA gt P le Ucr 21 2mW gt AT Pos Run 33 C 2 Omron 1 36 9mA gt Pol U 5U1mW gt AIR DC th JA Now the resistance for driving the basis of the transistor has to be chosen The high level output voltage of the NOR gate is at least 4V The DC current gain is at least 50 and the base emitter voltage is 0 7V at most To ensure that the transistor is saturated the DC current gain is divided by 10 But if in this case the basis current exceeds the maximum value of 12 5mA half
96. ort appendix 2 as well as the user manuals on the enclosed CD appendices 5c amp 5d Biner Dominik Diploma thesis page 12 78 Power supply and motion system for planetary rover NALAIS h H S O yj en Tokyo February 20 2008 a waus SPRAF Chuo University 3 3 3 Approach how to use batteries and charging equipment Now it has to be defined how the material is going to be used First of all some definitions A battery unit consists of two 4S 4800mAh battery packs connected in series Overall there are four battery units After charging balancing the balancer has to be disconnected from the battery because it puts an extremely small drain on the battery 0 5mA and it prevents the discharge of the batteries The idea is to always use two battery units together in parallel because so the current drawn is distributed on the two units The advantage of the current distribution is that there will be less heat creation in each pack and as the current is smaller the capacity of the battery packs can certainly fully be used see graph below Furthermore during the discharge of one pair of battery units the other one can be charged As it can be seen in the graph below when using the batteries with a small current the cell voltage changes much more as with a high current With a high current the cell voltage stays more or less constant during most of the discharge time But this doesn t
97. otion of the rover is much higher 4 2A and thus during this time the current will be higher than the given nominal current of 10A Assuming that the 3 52A are constant and that all 6 motors start at the same time the current for each unit will be 6 4 2A 3 52A 2 14 36A during 75 of the period and during the remaining 25 at 3 52A 6 4 2A 2 10 84A Thus the average current is of 0 75 14 36A 0 25 10 84A 8 06A which corresponds to a voltage of Uout Uret Ki Ip 2 2V 208 33 a 8 06A 3 88V But as the current exceeds the measuring range of the sensor the sensor s output voltage will saturate at 4 5V and 0 5V respectively This results in a wrong average voltage of 0 75 4 5V 0 25 0 5V 3 5V after RC filter However don t have enough information to completely dimension this part And as the time is too short decided to leave it like that especially because it s more important to set up the concept The final reference voltage values have to be chosen when the current values are definitively defined and determined by tests respectively Furthermore the measurable current range of the sensor may have to be adapted Biner Dominik Diploma thesis page 51 78 Power supply and motion system for planetary rover NN Hes so wan s OPpRke Tokyo February 20 2008 Chuo University 4 5 1 1 Simulation of the circuit To verify the functionality of the RC filter simulations with the softwa
98. p w Je Ea Tokyo February 20 2008 Chuo University 24 Roy Figd2 gt Uns Unnp Ura Urn 403V U 3 95V Ce gt Uran EM VD Piwa SMW 3 2b Row Fig 13 gt U kaiow ax U kai a en U ron U outra 4 6V Ukaw 3 53V R U kaow san Ua 1 07V Ur 1 07V a 3low 4low Ey gt Ursow 20 6MV gt Pasy 0 39 uW A _ 3a R Fig12 gt Uw U 395V U Pay Kwa 28mW max R 3b Row Fig 13 gt U kaow nan U oita U or R3low hax U sitna 4 6V U ee 3 53V an 20 6mV OT aisan Ure 1 05V gt Pi e O 4 At last the power dissipation of the resistances of the standard differential amplifier see fig 10 used for the measure of the first cell s voltage is calculated As the gain is 1 the resistances are the same R R _ U len U cell ngs eae a R R 2 2 2V Cell az 44V U U 2 U DM 86 43uW max So how it can be seen the wattage of each resistance is very low and far from s watt Biner Dominik Diploma thesis page 35 78 ooo Power supply and motion system for planetary rover VALAIS H e S S o WALLIS C tp m x ea Tokyo February 20 2008 Chuo University 4 4 1 1 Simulation of the circuit To verify the functionality of the circuit a simulation with the software OrCAD is done As the LMV324 is not contained in the libraries of the program the circuit with the LM324 is simulated
99. pendix 1b are expensive to manufacture So the idea is to use a pentagon typed wheel for hardening and a circular wheel with lugs in series to the aforementioned wheel to create the shearing effect see picture below By means of the actively articulated suspension the charge given on each wheel can be controlled and thus optimise the effect of each wheel Due to the limited time and that the development of the power supply as well as the speed regulation of the motors have a higher priority this approach has to be analysed by Dr Eng Kojiro lizuka The experimental system see fig 8 amp 9 of appendix 1b has to be adapted as this system is only for tests with one wheel Wheels 1 Pentagon typed wheels Rover Body 2 2 Circular wheels with lugs Seas Fig 1 Sketch of the new wheel placement use of circular and pentagon shaped wheels Biner Dominik Diploma thesis page 9 78 ooo Power supply and motion system for planetary rover NALAIS a Hes so wiis cp m pas Tokyo February 20 2008 jaliste SS 7 K F Chuo University 3 3 Power supply Lithium polymer batteries The charging of lithium polymer batteries LiPos is delicate The charging has to be done with constant power and the voltage of each cell has to be within the range of 3 0V and 4 2V After charging the voltage of all cells in the pack has to be the same balance between the cells For these reasons it would be a great ad
100. puts REF and REFADJ are bypassed to ground with capacitors DGND MAAXLAA MAX197 Vpp 5V REF uP REFADJ Tarp nF CONTROL 4 oor ET INPUTS OUTPUT STATUS ANALOG INPUTS NE uP DATA BUS Fig 30 Wiring diagram for the conversion of the cell voltage value A D converter Remark The circuit for adjusting the reference voltage see fig 25 is not shown Biner Dominik Diploma thesis page 45 78 oo Power supply and motion system for planetary rover M VALAIS H es so WALLIS C puk Tokyo February 20 2008 Chuo University 4 4 4 1 2 How to start and read a conversion A conversion is initiated with a write operation control byte which selects the analogue channel and configures the MAX197 To start a write cycle WR is set low Of course to enable the device CS has to be low during this time As aforementioned after the write pulse on WR the acquisition interval of six clock cycles is initiated The sampling interval start of conversion occurs at the end of the acquisition interval The conversion period lasts for 12 clock cycles Thus overall it needs 18 clock cycles to complete a conversion hence 11 54us with a clock frequency of 1 56MHz Remark Writing a new control byte during the conversion cycle will abort conversion and start a new acquisition interval To read the result of the conversion RD has to be low and of course CS too As mentioned before when
101. r 30 W gt Wied total W ced 12V regulator W sed 24V regulator 66 w nd N _ n 2 case U 12V regulator Ug 24V regulator U 24V regulator U aise gt used 12V regulator Un 12V regulator U ii 12V regulator i I 12V regulator 24 W gt W cca 24V regulator Un 24V regulator Us 24 V regulator Mou 24V regulator Lsi ee 42 W gt used total W ca 12V regulator 7 W sea 24V regulator 66 W f ex Ln seer 5A Lu 24V regulator 2A gt 1 case U U in 12V regulator in 24V regulator U sata Weg 12V regulator Ua 12V regulator E U oi 12V regulator Le 12V regulator 90 W W sed 24V regulator U 24V regulator U 24V regulator de 24V regulator 12 W gt W sea total W sea 12V regulator W sea 24V regulator 102 W nd a _ u a CONC Un 12V regulator U ou 24V regulator U 24V regulator U viini W sea 12V regulator U 12V regulator U sions tease die 12V regulator 60 W W cca 24V regulator U 24V regulator U on A ela j Ta 24V regulator Li byte 42 W W sed total W sed 12V regulator W sea 24V regulator 102 W Remark For the calculation of the losses for the second case the output currents of both regulators have been summed Of course it s the input current of the 12V regulator that is added to the output current of the 24V regulator see fig 6 But the input and the output current of the 12V regulator have the same value As it
102. r a current of 5A nominal and a maximal current of 10A But due to the filtering the average current is measured and thus these voltages have to be adapted As due to the motor speed regulation described in chapter 3 4 the current drawn from the battery is rectangular admitting a constant battery current and a high motor s inductance respectively the average current is lower than the nominal motor current ee L rom motor 2m 1 with m duty cycle of PWM signal The 12V DC motors used for moving the rover draw a nominal current of 1 08A with a voltage of 12V see datasheet of the motor on the enclosed CD appendix 5a Overall there are six motors and hence the maximal total nominal current is 6 48A For reaching an average voltage of 12Vdc the duty cycle of the PWM signal is 75 at most battery voltage at 24Vdc With it the maximal average current delivered by the batteries for the motors is weren Tnommany 210 1 3 244 For the current of the smaller motors used for the steering of the rover the average is not calculated as the current is relatively small The total nominal current is given as 10A and so there are 3 52A left 6 48A for the motors Therefore in average we get a total current of 3 524 3 24A 6 76A which is distributed on two battery units So due to the motor speed regulation the nominal average current for one unit is 3 38A 2 9V instead of 5A 3 24V Moreover the starting current of the motors used for the m
103. rance of the amplifier the capacitor sees a total resistance of R parallel to Ro With a cut off frequency of 10Hz the required capacitance is in the range of uF Instead of increasing the resistance values anymore the frequency is set to 50Hz Therewith we get the following capacity value Biner Dominik Diploma thesis page 57 78 ooo Power supply and motion system for planetary rover Tokyo February 20 2008 Hes so WE SparxF FRE eos kenka Chuo University gt C ae 20 Ro 1 1 _ _ 50Hz fe 2a R C RR R 7 5kQ gt C 4244nF EI2 C 470nF R R 45 15Hz gt fara Zereal 27 R B pe se a en 2a R C RF R R R ee 3 75kKQ gt C 848 8nF EI2 C 820nF 1 S fora 51 76Hz So the complete current measuring circuit with the LM324 is the following AW Oto the load es battery 1 470n 4 ayt AM 8 in 15k 15k 10m 4 AWW AW gt 15k 15k 470n 750k 5Vdc 5Vdc 5Vdc A 10k Idischarge gt 10A 5Vdc Imss 8 Inominal exceeded 1M ref 2 5V 9 _ S 5Vdc 5Vde ref 1 25V 9 10k 5Vdc I Icharge gt 7 7A 5Vde Inominal exceeded ref 1 a Sf 1 925V8 5Vde 5Vde Fig 43 Electrical schema of the battery current measuring circuit with shunt and LM324 page 58 78 Diploma thesis Power supply and motion system for planetary rover
104. re OrCAD are done The simulation circuits are as follows 150k 150k Uin Uout Uin Uout v1 v v V1 0 5 v2 v 1Vac 100n V2 4 5 100n OVde PW 35u PER 50u 0 0 0 0 Fig 35 Simulation schemes of the battery current measuring circuit with current sensor LEM To check the cut off frequency of the filter the voltage given by the current sensor is represented with the AC voltage source V1 left scheme of fig 35 The source provides a sinusoidal signal with amplitude 1V The frequency of the signal is varied from 0 1Hz to 100kHz and we get the following result 166 666m 385 685u 2 9919 2 9915 166 666 604 1 0000K i 966 666 80 T T 1 100mHz 1 0Hz 10Hz 100Hz 1 0KHz 10KHz 100KHz o 20 LOG10 V UOUT V UIN Fig 36 Simulation result of the battery current measuring circuit with current sensor LEM On the y axis the amplification in dB is given Aas 20 log A As we can see everything is like wished For low frequencies the amplification is 1 OdB and the cut off frequency of the filter at 3dB is at 10 6Hz see upper Probe Cursor window After that as we have a first order filter the slope is about 20dB per decade see lower Probe Cursor window Finally the current sensor will provide a rectangular signal with a certain offset Thus to verify if the filter gives as desired the average value the voltage given by the sensor is represented with th
105. re weight of the rover Speed of the rover is 0 1 m s gt Wyig 4 m v 5 2mJ Speed of the rover is 0 2 m s gt Wyig m v 20 8mJ 0 6Ah difference gt totally 2 4 Ah more capacity SO Wye Quig U nomini 724 As aforementioned with the 4800mAh type the total available capacity is 19 2 Ah which affords an autonomy time of 1 hour and 55 minutes To augment this time more than 4 units are necessary But the batteries are mounted under the body of the rover and there is not more space available Thus additional units would have to be placed somewhere else for example laterally in front or at the rear of the rover One battery unit consists of two battery packs and the maximal allowed dimension of one unit is 88mm x 175mm x 50mm see requirements specification in chapter 2 2 1 The dimension of each pack is 44mm x 150mm x 40mm and they are placed abreast Thus one battery unit is 88mm x 150mm x 40mm big which is within the given limits The batteries can deliver a current up to 96 amperes 20C which is completely sufficient For charging the batteries with a current of 1C thus 4 8 ampere it needs about 150 watt of power for each pair of battery pack Therefore for charging all battery units at the same time 600 watts are required 3 3 2 Selection of the charging equipment For charging the lithium polymer batteries the charger EOS 1210i is deployed It allows charging battery packs with up to 12 cells It charges the
106. rs In order that it doesn t need A D converters and a microprocessor for realising the first dis charge tests of the batteries foremost the detection of this value is realised by comparing the cell voltages to a reference voltage by means of analogue circuits But finally this detection will be taken over by the microprocessor This approach using A D converters is described below in chapter 4 4 4 To lead the voltage of each cell to the differential amplifiers the balance harnesses of the batteries are deployed The differential amplifier is realised as follows 5Vdc R R U U U with Gain G 2 R R 1 1 Fig 10 Differential amplifier Biner Dominik Diploma thesis page 25 78 ooo Power supply and motion system for planetary rover 7 7 NALAIS i Hes so wai ch Tokyo February 20 2008 o SPRAY Chuo University For realising the amplifiers the integrated circuit LMV324 is deployed which can be single supplied with 5Vdc It s a rail to rail operational amplifier and so the use of a 5V supply voltage causes no problems Moreover it s cheap and as it s a SMD component it allows a space saving design For more details about the LMV324 see the datasheet on the enclosed CD appendix 5f As comparator the LMV339 is deployed It can also be single supplied with 5Vdc and it s an SMD component as well It has the advantage that its output is open collector and therefore allo
107. s Now the left side of the converter pin 1 to 14 there you can see the digital in and outputs as well as the clock pin CLK Such as for the reference voltage the clock can be given externally or the internal one is used In our case the internal clock is deployed in order that the microprocessor doesn t have to provide it To set the clock frequency a capacitor is put between this pin and ground The picture below shows the linear relationship between the internal clock period and the value of the external capacitor 1500 1000 INTERNAL CLOCK PERIOD ns 500 0 0 50 100 150 200 250 30 3 CLOCK PIN CAPACITANCE pF Fig 26 Relationship between the internal clock period and the external capacitor A D converter In our case a 100pF capacitor is used like shown in figure 21 This typically sets the frequency to 1 56MHz The clock mode is selected by means of the bits D6 and D7 of the control byte PDO and PD1 For our application D6 PDO is set to 1 and D7 PD1 to 0 Biner Dominik Diploma thesis page 43 78 ooo Power supply and motion system for planetary rover M H es s O ren C p Jt k Ea Tokyo February 20 2008 IN Chuo University PD1 PDO DEVICE MODE 0 Normal Operation External Clock Mode JEJ Normal Operation Internal Clock Mode Standby Power Down STBYPD clock mode is unaffected Full Power Down FULLPD clock mode is unaffected Fig 27 Table for the
108. s not calculated because the voltage over the shunt resistor is very low max 100mV and therefore also the one on the amplifier s resistances As the amplified voltage is very small for the realisation of the PCB some 10 PCB Printed Circuit Board A PCB is used to mechanically support and electrically connect electronic components using conductive traces copper Biner Dominik Diploma thesis page 59 78 ooo Power supply and motion system for planetary rover VALAIS H e S so WALLIS S ib H gt Tokyo February 20 2008 Chuo University conditions have to be fulfilled In order not to introduce an additional measurement error due to the printed circuit board track resistance both lines to positive and negative entrance of the op amp must be of the same length same resistance Moreover it s advantageous if the conductive path from the shunt to the amplifier is as short as possible 4 5 3 1 1 Simulation of the circuit To verify the functionality of the circuit a simulation with the software OrCAD is done The simulation circuit is as follows Fig 45 Simulation schema of the battery current measuring circuit with shunt and LM324 To check the functionality of the filter the voltage on the shunt resistance is represented with the AC voltage source V10 The source provides a sinusoidal signal with amplitude 100mV The frequency of the signal is varied from 0 1Hz to 10KHz and we ge
109. selection of the clock mode A D converter Remark The device possesses a power on reset which sets the clock mode to external mode As it can be seen in figure 27 the power down mode is also determined by these two bits But once the desired clock mode is selected changing these bits to program power down does not affect the clock mode if PD1 0 then the clock mode is chosen with PDO else the state of the bit PDO defines the power down mode In our case the power down modes will most likely not be used But depending on how much time elapses between the conversions they can be used to save power When the power down is provoked by means of these two bits it becomes effective only after the end of conversion In all power down modes the interface remains active and the conversion results can be read The device returns to normal operation on the first falling edge of the WR signal For more information about the difference between the two modes refer to the datasheet on the enclosed CD appendix 5m page 14 By pulling low the signal on SHDN pin 6 the device is put into the full power down mode But in this case the power down becomes effective immediately and the conversion is aborted In our case this pin is connected to the power supply Vpp as shown in figure 21 Thus this signal is not controlled by the microprocessor uP The digital inputs CS WR RD and HBEN are all connected to the uP and their state given by it all active
110. state As RS latch the integrated circuit M74HC279MIR is used It works with a supply voltage of 5Vdc and is a space saving SMD component It has four RS latches and thus only one integrated circuit is necessary for realising the driving circuits of each unit Moreover two of the four latches have two S inputs which are internally relayed to an AND gate and therefore for this two the signals of both measuring circuits can be applied without the need of additional logical gates For more detailed information see the datasheet on the enclosed CD appendix 50 The truth table of this RS latch is as follows SIR Q CIEI a Dh a aes ENEI a ae Q0 unchanged Fig 39 Truth table of the RS latch M74HC279 Remark For the latches with double S input 1 both S inputs high 0 one of both inputs low internal AND gate 24Vdc Thus finally the driving circuit is the following uP 1 uP2 signals from microprocessor 0945 MIM QIalD signals from analogue circuits battery unit 1 Ucell_mes 1 Ibatt_mes 1 signals from analogue circuits battery unit 2 Ucell_mes2 1 to driving circuit gt for battery unit 2 signal Q Ibatt_mes2 gt 7408 Fig 40 Driving circuit for the relays used for switching between the charge and the discharge of the batteries switching through analogue circuits possible uP independent final version The conditions in the no error stat
111. stem for planetary rover M H es s OU WALLIS gt en Jn X Ea Tokyo February 20 2008 IN Chuo University Domicile in Japan Vicor Japan Co Ltd 6F POLA 3rd Building 8 9 5 Nishi Gotanda Shinagawa ku Tokyo 141 Japan Tel 81 0 3 5487 5407 Fax 81 0 3 5487 3885 Homepage www vicr co jp Sales and distribution For information about suppliers for different countries visit the homepage www vicr com http www vier com company contact us 9 4 3 Deutronic Headquarters in Germany Deutronic Elektronik GmbH Deutronicstrasse 5 D 84166 Adlkofen Tel 49 0 8707 920 199 Fax 49 0 8707 10 04 Email sales deutronic com Homepage www deutronic com Domicile in Japan Jatek Ltd 2 5 53 Minowa cho Kohoku ku Yokohama Kanagawa 223 0051 Japan Tel 81 0 4 5562 4483 Fax 81 0 4 5562 7800 Email e okamura jatek co jp Homepage www jatek co jp Sales and distribution For information about suppliers for different countries visit the homepage www deutronic com http deutronic com kontakt distr world htm Biner Dominik Diploma thesis page 76 78 ooo Power supply and motion system for planetary rover Y7 NALAIS Hess O Waits C cp y x a Tokyo February 20 2008 Chuo University 9 5 Manufacturer of MOSFET drivers company IRF Headquarters in the USA International Rectifier 233 Kansas Street El Segundo
112. t the required driving power can be calculated as follows EB Qs AU ss one gt Tas z switching frequency To exactly determine the total amount of losses due to the switching of the transistors it s necessary to use software like OrCAD or creating an according model in MATLAB or other similar programs But to create appropriate models is quite difficult and the losses are also depending on the circuit layout Therefore it s better to determine the wastages by measures on the circuit Once the amount of losses is known it can be defined if it needs a heat sink By means of the thermal resistance between junction and ambient Rea the temperature of the junction can be determinate as follows T ambient P TOSS top junction R This temperature has to be lower than the highest allowable junction temperature given in the datasheet If the temperature gets too high a heat sink is necessary To determine what kind of heat sink is necessary its maximal possible thermal resistance has to be calculated In case of the use of a heat sink the thermal resistance between the junction and the ambient Rea is composed of Rejc Recs Resa where Resa is the thermal resistance of the heat sink Rejc is the thermal resistance between junction and case and Recs is the one between the case and the head sink Therefore the highest admissible thermal resistance of the heat sink is calculated as follows T P R T P R j
113. t R 55 7kQ El12 R 56kQ Bans 1 00 R R R R R R Nn gt G real Like before the first cell can be measured with a standard differential amplifier see fig 10 because the voltage U is low enough R U 44V G gt R G R max R 1 x a 1 G 2 2V U Pp 1 max max R R For reaching a gain of 1 the values for the resistances R and R2 of figure 10 have to be the same R R 56kQ Biner Dominik Diploma thesis page 32 78 ooo Power supply and motion system for planetary rover He S soW WALLIS gt pa Ea Tokyo February 20 2008 rochschule Westschwe Chuo University So the circuit for measuring the cell voltage with the LMV324 is as follows 10k 3 7Vde cell8 OV gt cell voltage too low 3 7Vde cell7 IMIS__Vref 3 7Vde cell2 3 7Vde cell1 Fig 15 Electrical schema of the battery cell voltage measuring circuit with LMV324 The circuit will be realised with SMD components in order to be more space saving Therefore it s advantageous if the power of each resistance is less than s watt The calculation is realised for the differential amplifier which measures the voltage of the 8 cell because the voltage on its resistances is the highest Biner Dominik Diploma thesis page 33 78 On Power supply and motion system for planetary rover DN H es s O WALLI gt p J
114. t the following result _ l 1 6666 27 952 A 45 186 24 944 ff if 44 186 3 8877 1 8823K 1 6346 16 666K 19 987 i 8 9977K 21 821 20 T T T 100mHz 300mHz 1 0Hz 3 0Hz 10Hz 30Hz 100Hz 300Hz 1 0KHz 3 0KHz 10KHz o 20 LOG10 V IMESS V USHUNT Frequency Fig 46 Simulation result of the battery current measuring circuit with shunt and LM324 On the y axis the amplification in dB is given Aas 20 log A As we can see for low frequencies the amplification is 27 95dB which corresponds to the desired gain of 25 The cut off frequency of the filter at 3dB thus 24 95dB is at 45 2Hz see upper Probe Cursor window After that as we have a first order filter the slope is about 20dB per decade see lower Probe Cursor window Biner Dominik Diploma thesis page 60 78 oo Power supply and motion system for planetary rover M H es s O ae C en It k Ea Tokyo February 20 2008 IN Chuo University 4 5 3 2 Use of an inverting amplifier If the battery packs of one unit are in series the shunt resistance is placed so that it s connected to ground see fig 43 For that reason the use of a differential amplifier is not necessary and the amplification of the shunt s voltage is done with an inverting amplifier This has the advantage that fewer components are required and the
115. the battery Moreover it puts an additional resistance between the batteries and the load charger The measure with the current sensor from LEM doesn t influence the line of which the current Biner Dominik Diploma thesis page 63 78 oo Power supply and motion system for planetary rover NALAIS a Hes so wiis cp m pas Tokyo February 20 2008 jaliste SS 7 K F Chuo University is measured and it provides directly an easily measurable signal no amplification necessary and only few additional components are required to get the average value Moreover the measuring accuracy is very high up to 0 2 and it allows the determination of the maximal current value in a relatively easy way But it s more expensive As we can see the measure of the current with a shunt resistor has many disadvantages compared to the one with the current sensor LEM The only disadvantage of the LEM is the price Deductive suggest using the method with the current sensor from LEM how already mentioned to begin of chapter 4 5 If the measure should be done with a shunt resistance the method described in chapter 4 5 3 2 is applied use of inverting amplifier because it requires less components the dimensioning of the filter is easier and the gain can easily be adjusted by means of a potentiometer 4 5 5 Detection of the end of charge As mentioned in chapter 3 3 3 page 14 the charger 1210i from Hyperion detects
116. unction ambient TOSS tor QA ambient LOSS jot JA ac Res Rosa __ Junction max ambient gt Rey Rgc RK acs losStot As MOSFET the K2936 is deployed It can be driven with a gate source voltage of only 4V and therefore to supply the MOSFET driver with 5Vdc is sufficient The K2936 has a very low Rpscon resistance with a control voltage Uaes of 4V only about 15mQ Thereby the conduction losses will be very low as the nominal motor current is just about one ampere Furthermore the reverse recovery time of the body drain diode is small 50ns The maximal drain source voltage is 60V and thus higher than the maximal supply voltage It can drive a drain current up to 45A but nevertheless has a low total gate charge For the maximal battery voltage of 34V it s only about 40nC For more details about the transistor and the Maxon DC motors see the datasheets on the enclosed CD appendices 5a 5b amp 5e The choice of an appropriate MOSFET driver is taken over by Shimanuki Toru Biner Dominik Diploma thesis page 23 78 ooo Power supply and motion system for planetary rover 1 NALAIS i Hes so waius cp rh se pas Tokyo February 20 2008 a COC IN r m F Chuo University 4 Realisation suggestions for the power supply 4 1 Introduction to this paragraph As mentioned in the previous chapters the analysis of the suggestion for the new wheel placement chapter 3 2 and the realisatio
117. vantage to be able to use products already on the market for charging the batteries safely Of course the temperature has to be within the allowed limits at all times The batteries as well as the charging equipment are chosen from the product range of the company Hyperion Hyperion is a provider of R C products and offers quality components at a reasonable price For contact information of Hyperion information about the charging equipment and general sources about LiPos see chapter 9 3 3 3 1 Selection of the batteries The nominal voltage of a lithium polymer battery cell is 3 7V During the discharge of a battery pack the cell voltage drops The power supply will be dimensioned so that the discharge will be stopped when the voltage of one cell reaches about 3V Therefore it needs 8 cells connected in series to generate the required 24V The highest amount of battery cells in one pack is only six Therefore it needs two packs connected in series to reach the demanded voltage To be able to use only one battery charger for charging two packs at the same time the packs have to be identical Thus battery packs with 4 cells 4S type will be used In order to increase the autonomy time of the rover as much capacity as possible is needed As a result following battery packs would be suitable Hyperion CL 4S 4800mAh 96 0A Continuous 20C Weight 515gr Size 44 x 150 x 40 mm Hyperion CL 4S 4200mAh 67 2A Continuous 2100 2P 16 2
118. ver and the smaller one for the steering Normally a first adaptation of the voltage is realised with DC DC converters but in this case they are too big and cause too many losses The average supply voltage of the motor which determines the motor speed has to be generated directly from the battery voltage Remark The requirements specification has been written by myself For it used information about LiPos gathered during the summer vacation before coming to Japan as well as the information get through discussions with my person in charge Dr Eng Yasuharu Kunii Unfortunately I didn t take notes of the sources used during the summer vacation With lithium polymer batteries the current is mostly given by a multiple of their capacity For example with a 2 7Ah battery 1C correspond to a current of 2 7 amperes 2C would be 5 4 amperes and so on Biner Dominik Diploma thesis page 7 78 Power supply and motion system for planetary rover sp cialis e occidentale Hes S o WALLIS gt pm Ea Tokyo February 20 2008 Chuo University 2 3 Operating schedule Besides the diploma work have to follow Japanese language lessons at the Tama Campus of Chuo University Until the winter vacation have seven lessons per week from Wednesday to Friday Therefore during this period lm only working two days a week on this project Additionally every Thursday afternoon lead an English lesson for Japanese
119. with a RC low pass filter Therewith the ripple of the current is also eliminated The cut off frequency is set to 10Hz and we get the following values pa ei gt ER DEN 27 R C 2m R f R 150kQ gt C 106 1nF El2 C 100nF gt fovea 10 61Hz 28h 3C Remark Notice that due to the filtering the current measure doesn t provide the maximal delivered current value During the high time of the PWM signal used for the motor speed control the current is higher To get the maximal value the signal provided by the sensor has to be transmitted directly to the uP which on its part has to take measures fast enough at least at twice the frequency of the PWM signal The filtered voltage is relayed to the A D converter MAX197 in order to allow the Biner Dominik Diploma thesis page 49 78 ooo Power supply and motion system for planetary rover NALAIS H e S S o WALLIS p Tokyo February 20 2008 28 S0 SPRAY Chuo University examination of the current as well as the calculation of the battery capacity by the uP The converter and the use of it have already been described in chapter 4 4 4 1 The converter MAX197 has eight analogue inputs and therefore only one integrated circuit is required for transmitting the current value of each battery unit to the microprocessor If the digital signal mentioned at the beginning of chapter 4 5 signalising when the current exceeds the nominal value has
120. ws a wired and connexion Thus there is no need of logical gates to generate a digital signal that shows the state of the battery cells The datasheet of the LMV339 is also on the enclosed CD appendix 5g The reference voltage for the comparator is given by a potentiometer of 1MQ As it can be seen in figure 10 the input voltage U of the LMV324 is R Cat P RR The input common mode voltage range of the LMV324 is from OV to 4V So the input voltage U has to be 4V at most Hence for measuring the voltage of the upper cells the circuit of the differential amplifier shown in figure 10 has to be modified as follows Fig 11 Modified differential amplifier high common mode voltage Remark The LMV324 is only available with SMD case By adapting the gain of the differential amplifier the maximal output voltage can be chosen Therefore the LM324 is deployed to allow making the first tests because it s very cheap and is available in the laboratory bought before Its input common mode voltage range is from OV to 3V This type is not a rail to rail amplifier and with a supply voltage of 5V the output voltage can only reach 3V at most For more details about the LM324 see the datasheet on the enclosed CD appendix 5h Due to the limited output range for the final realisation of the circuit the rail to rail amplifier LMV324 is used because in that case a bigger voltage span is available This brings the advantage that the differenc

Dominik Biner Power supply and motion system for

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