Sensorless Control of BLDC Motor using Infineon XE164
Contents
1. Crossing value Offset Bemf gt Zero Crossing value Offset Increment Counter Increment Counter r Y Yes C b State 2 Y C Return Application Note 21 V1 0 2010 03 AP16173 e e In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller C Return Application Note Bemf gt Zero Crossing value Software Implementation v NO Ramp J Yes Motor Stop Read Bemf Value Increment Counter y No C Return Bemf lt Zero Crossing value Increment Counter Yes C Return gt Capture time between two BEMF detection Y Load CCU60 amp CCU61 Restart Timer Y State 3 Slope slope 2 Y C Return 22 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation No Yes Motor Stop Read Bemf Value Yes Bemf lt Zero Crossing value Bemf gt Zero Crossing value Increment Counter Increment Counter No C ila gt Yes Yes C Return Slope 3 Slope 2 Capture time between two BEMF detection Y Load CCU60 with Half of measured time Y Load CCU61 with2. Increment A 3 4 Where Freq Increment T Target Value Freq Increment A Actual Value Volt Increment T o Mdet Fpem 0 3 5 FcPU Volt Increment A Where Vac DC link Voltage E own PWM frequency 20kHz ETT CPU frequency 66MHz Volt increment T Target Value Volt increment A Actual Val T13 Pre scaler 1 Start Duty _ Cyele T art Duty Cycle T Fepu 3 6 Fpwm Where Start Duty Cycle T Target Value Start Duty Cycle A Actual Value Application Note 17 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation Table 4 Startup Parameter Value Parameter Physical value Unit get Value BEMF Start Frequency SB BEMF Check Frequency ee deo 5625 BEMF End Frequency 40 o 6250 Frequency Increment 144 Voltage Increment V S 106 Start Duty Cycle 165 Increment Frequency Increment Voltage Duty Cycle Update Anlge gt Commutation Angle C Return gt Load next commutation pattern in MCMOUTL shadow register C Return D Figure 11 Flowchart for Rampup Function Application Note 18 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 4 1 2 Close Loop Mode Sensorless Mode In this mode the commutation time is c
3. Loop Speed Control Application Note 10 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 Software Implementation The implementation of Sensorless Speed control of a BLDC motor with a XE164F microcontroller and peripherals is discussed in this section 3 1 Overview Figure 8 shows an implementation of Sensorless Speed control of a BLDC inverter fed motor in closed loop Inverter XE164F CC60 COUT60 CC61 B Driver BE E COUT61 IC CC62 COUT62 BLDC Motor Vdc Back EMF Measurement Figure8 Block Diagram for Sensorless Control of BLDC Motor Three on chip peripheral modules are used to implement this application in the XE164 microcontroller at any given time e CCUGE CAPCOMGE e ADC Analog to Digital Converter e General Purpose Timer Unit GPT1 The software is divided into several routines Main Loop Initialization CPU I O ports CAPCOM6 ADC and GPT1 Interrupt Routines e CAPCOMG T13 Period Match T13 Compare Match T12 Compare match of Channel 2 T12 Period Match and CTRAP e GPT Timer 2 Over Flow Application Note 11 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation All the parameters such as voltage frequency current and speed used in this al
4. 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 4 3 PI Controller Function A PI controller is used for regulating speed The error difference between the reference speed and the actual speed is fed to the controller The PI controller functionality is shown in Figure 16 Duty Cycle Proportional Gain Integral Gain Figure 16 Block Diagram for PI controller In continuous time domain the duty cycle output is given by Duty Cycle K error K error dt 3 8 In discrete time domain the PI controller is implemented as described by the following equations Yn k 1 Yn k Ki e k Y k 1 Yn k 1 Kp e kK 3 9 Where Ki Integral Gain Kp Proportional Gain e k Error value y k 1 Next computed duty cycle yn k Integrated error value till last computation yn k 1 Current Integrated error value The actual Kp and Ki values are scaled and will be used in target as follows Kp T kp 2 64 Ki T ki 2 3 10 Where Kp T and ki T are the Scaled Proportional and Integral Gain values used in software Application Note 25 V1 0 2010 03 etc AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation The PI controller functionality implementation is written in assembly and uses the microcontroller MAC unit functiona
5. CCU60 value Delay Y Stop and restart timer T12 Y Load next commutation pattern in MCMOUTL shadow register Y Return Figure 14 Flowchart for Commutation Function Application Note 23 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 4 2 Speed Rampup Function In the Speed Rampup function the user reference speed value is determined by user input via POT The motor reference speed is gradually increased decreased up to the user reference speed with the rate of speed increase decrease based on the speed slew rate RPM Second The speed slew rate RPM Second is based on the function call rate and the ramp scheduler value The function call rate is fixed for a particular PWM frequency for 20 kHz the function call rate is 50 us So the ramp scheduler value is calculated from the required speed slew rate and PWM frequency 1 Required Slew Rate Function Call Rate sis oe RampScheduler z Rampup Y Read Speed reference value from ADC register1 RampScheduler gt RampCounter RampSchdeuler 1 Speed Ref Set Speed Increment Speed Ref Increment RampSchdeuler Speed Ref gt Set Speed Decrement Speed Ref Figure 15 Flowchart for Speed Rampup Function Application Note 24 V1 0 2010
6. Cinfineon XC2000 XE166 Family AP16173 Sensorless Control of BLDC Motor using XE164F Microcontroller Application Note V1 0 2010 03 Microcontrollers Edition 2010 03 Published by Infineon Technologies AG 81726 Munich Germany 2010 Infineon Technologies AG AII Rights Reserved LEGAL DISCLAIMER THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN FUNCTIONALITY CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES COMPONENT THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION INFINEON TECHNOLOGIES HEREBY DISCLAIMS ANY AND ALL WARRANTIES AND LIABILITIES OF ANY KIND INCLUDING WITHOUT LIMITATION WARRANTIES OF NON INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD PARTY WITH RESPECT TO ANY AND ALL INFORMATION GIVEN IN THIS APPLICATION NOTE Information For further information on technology delivery terms and conditions and prices please contact the nearest Infineon Technologies Office www infineon com Warnings Due to technical requirements components may contain dangerous substances For information on the types in question please contact the nearest Infineon Technologies Office Infineon Technologies components may be used in life support devices or systems only with the express written approval of Inf
7. EE 6 2 3 Three Phase INVerter arnie ot T 2 4 Sensorless Mode of Operation iii 8 2 5 FS AG e EMF IVI AS UE meN NR TETTE ETT m 9 2 6 Speed Control OF BLDG MOLOF ironia 10 3 Software Implementation coscssctcs ence cevecereneccedepucsteneupartteseunesnedetscetensnedsuuneauevancuenescubeaasescadsameutemeventeneue 11 3 1 VONIS 11 3 2 PernpheralConiguratoN 12 3 2 1 Fiat MIP OA 12 3 2 2 CAP GONG UZ nm 12 3 2 3 ADC MAINZ ANC qM MEET delves seme wack seice sees E E AE EE 13 3 2 4 CO MEM EE EA ire oie E 13 3 3 Interrupt Service Routines ISRS ei 14 3 4 CCUGO T T3 Period Match ISR uius leer a 15 3 4 1 COMMUaton FUNCIOli sr 16 3 4 1 1 RSW LOO ed 1 00 PRE EAT 17 3 4 1 2 Close Loop Mode Sensorless Mode esses eene nnne nennen nnne nnn nina nnn nina nnns 19 3 4 2 Speed Rampup Function NSNRX 24 3 4 3 PI Controller FUNCHON MENTOR A e tt 25 3 5 TI COMIIEMACRISR TET PTEMRUTTEDPE ZVTE 27 3 5 1 Channel Selection Function siii lira alinea iii ite 2f 3 5 2 Compare amp Current Measurement Function i 28 3 6 CCU62 Compare Match ISR iii 28 3 7 T12 Period Match amp CTRAP ISR esseesssseessesesiieeeneeee n nnne
8. alculated based on the induced EMF in the inactive phase The motor speed will rampup from the start speed reference to the user speed As discussed in section 2 5 the Back EMF measurement should be synchronized with the PWM signal used for chopping In the implementation Timer T13 is used for chopping so the unexcited phase voltage is measured during every CCU63 compare match event When a new commutation pattern has been loaded into the MCMOUT register the unexcited phase voltage is measured for every CCU63 Compare ISR via ADC Demagnetization spikes will occur whenever a new commutation pattern is applied This spike will affect the Back EMF and may be interpreted as a zero crossing event In order to ignore this spike zero crossing detection is ignored for a predefined delay time after applying every new commutation pattern TEE Stop Mi Pos 00008 Demagnetization aem Spike Phase A Phase B J CHT 200 CH2 4004 LHS 2 00 Mi 1 00ms Figure 12 Phase Voltage at 100 Duty Cycle If the voltage values on two consecutive measurements are greater than the zero crossing value for positive slopes slope 1 or less than zero crossing value for negative slopes slope 0 then timer T12 will be stopped and the timer value is captured The commutation pattern is then updated in the MCMOUT register after half of the T12 timer value The following steps are required to accomplish this e Half of the T12 timer value should be loaded i
9. ection is also implemented in the software If the motor current value exceeds the set limit value the motor will be stopped The maximum current range is defined as Vadcref MA 3 11 T Rshunt Gop o Where V adcref ADC reference Voltage Rehun Current shunt resistor value Gop Amplifier gain In this implementation the 10 bit ADC value is multiplied by 8 The current scaling is 915 Ni malf 3 12 8 2 3 6 CCU62 Compare Match ISR During this ISR the Speed calculation function is executed The speed calculation needs the time between zero crossing values The time will be determined by Timer12 CAPCOMGE On every zero crossing the Timer T12 will be stopped and the time between zero crossing values is stored in a circular memory To reduce the measurement errors the time between two zero crossing events is averaged over 6 Pole pairs measured values The time taken by the motor to complete one rotation can be calculated from the sum of 6 Pole pairs measurement and the timer T12 resolution Tspeed Tinrot Tia t TeoePar 1 00 ee 3 13 Where T Time between two zero crossing events The speed is calculated using the formula MotorSpeed EE MM RPM 3 14 Topea T12 Re solution The step size of Timer T12 will determine the range of speed values that can be measured 3 7 T12 Period Match amp CTRAP ISR If the CCUG trap input becomes active or if the T12 Period
10. etail The advantages of the microcontroller peripherals are also discussed CAPCOMGE Capture and Compare Unit for modulation and PWM generation and the fast 10 bit ADC Analog to Digital Converter These peripherals are specifically designed for motor control applications The motor control software is written in both C and assembly This software uses the XE164F peripherals while the mathematical computations such as the PI control algorithm use the microcontroller DSP Data processing MAC Unit functionality 1 1 Motor Control using the XE164F Microcontroller The XE164F microcontroller has dedicated peripherals specifically designed for motor control applications The key features of the microcontroller are e High performance CPU with five stage pipeline e Interrupt system with 16 priority levels for up to 83 sources e Eight channel interrupt driven single cycle data transfer with Peripheral Event Controller PEC e Two Synchronizable A D Converters with up to 16 channels 10 bit resolution e 16 channel general purpose capture compare unit CAPCOM2 e Up to three capture compare units for flexible PWM signal generation CCU6x e Multi functional general purpose timer unit with 5 timers and quadrature decoders e On chip MultiCAN interface Rev 2 0B active with up to 128 message objects With the intensive autonomous use of dedicated peripherals designed for motor control CPU load can be reduced The CPU can then be used to perform o
11. gorithm are represented in the microcontroller in 1Q15 format i e bit15 is the sign bit and bit14 bitO refers to the value The equation for scaling is as follows Actual Value 21 Target Value Ns 3 1 Where Target Value Value passed to the microcontroller Actual Value Physical value Ns Normalization value maximum physical value The Normalization value is the maximum physical value usable in the microcontroller without overflow 3 2 Peripheral Configuration All the necessary initialization routines have been performed before the motor is started 3 2 1 Port Initilization P0 0 is used as output to Enable Disable the Drive Board 3 2 2 CAPCOME Initilization The CCU60 module is used to generate the PWM control signals for the inverter For this purpose the timers T12 and T13 the compare registers CC60SR CC61SR and CC62SR and the MCMOUT registers are used Timer T12 and Timer T13 operation are configured for edge aligned Mode and Timer T13 is also used for pulse width modulation to control the motor speed Dead time control is enabled for the six PWM signals to avoid shoot through current e P10 0 P10 1 P10 2 P10 3 P10 4 and P10 5 are used as outputs for the CCU60 Channel Port pins CC6x COUT6x e Enable Multi channel mode e Set the passive output level as High Based on Drive Board e Timer T13 Period value set to 50 us 20 kHz e Timer T12 configured for Edge aligned mode e MCMOUT regi
12. ineon Technologies if a failure of such components can reasonably be expected to cause the failure of that life support device or system or to affect the safety or effectiveness of that device or system Life support devices or systems are intended to be implanted in the human body or to support and or maintain and sustain and or protect human life If they fail it is reasonable to assume that the health of the user or other persons may be endangered ere AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller XC2000 XE166 Family Revision History V1 0 2010 03 Previous Version none Page Subjects major changes since last revision This is the first release We Listen to Your Comments Is there any information in this document that you feel is wrong unclear or missing Your feedback will help us to continuously improve the quality of this document Please send your proposal including a reference to this document to mcdocu comments infineon com Application Note 3 V1 0 2010 03 ere AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Table of Contents Table of Contents 1 INFOGUCHON siii E rea ira 5 1 1 Motor Control using the XE164F Microcontroller nnn 5 1 2 Hardware and Software Components ii 5 2 Principle of Sensorless Operation iii 6 2 1 NIOO I DEO NET 6 2 2 Principle of Op ratiONM R
13. know the rotor position to energize appropriate stator windings In sensor mode the rotor position is sensed using Hall Effect sensors embedded in the stator or an encoder In this application rotor position is estimated using the Back EMF Figure 1 Single Pole Pair BLDC Motor with Hall Sensor BLDC motors are commutated every 60 during a full cycle of 360 electrical so in total there are 6 steps in one cycle A transition from one step to another step is called commutation Two of the three coils are energized at any given time In each commutation sequence one of the windings is energized to positive power current enters into the winding the second winding is negative current exits the winding and the third is in a non energized condition Torque is produced by the interaction between the magnetic field generated by the stator coils and the permanent magnets Ideally the peak torque occurs when these two fields are at 90 degrees to each other and falls off as the fields move together In order to keep the motor running the magnetic field produced by the windings should shift position as the rotor moves to catch up with the rotor field What is known defines This sequence of energizing windings is known as Six Step commutation or Block Commutation The motor takes six steps to complete one electrical cycle for a three phase machine In general the relationship between mechanical and electrical degrees is as stated in equati
14. lem can be worse for applications that want to minimize switching losses by using a low PWM frequency 2 6 Speed Control of BLDC Motor The speed of the motor is directly proportional to the applied voltage The average voltage applied to the motor can be varied using Pulse Width Modulation PWM by switching the MOSFET on or off At 100 PWM duty cycle the motor will run at rated speed provided the rated dc voltage is supplied To operate the motor at a desired speed below the rated speed either the high side or low side transistor should be pulse width modulated Two control schemes are possible 1 Open loop speed Control Voltage Control 2 Closed loop speed Control In an Open loop speed control the duty cycle is calculated based on the set reference speed In a closed loop speed control the actual speed is measured and compared with the reference speed to find the error difference This error difference is supplied to a PI controller The output from the PI controller is the new duty cycle Duty Cycle Speed Ref gt Duty Cycle Commutation Estimation Logic e Inverter Figure6 Open Loop Speed Control Figure 6 shows the open loop speed control of a BLDC motor The duty cycle for a set reference speed is estimated based on the nominal base speed of the motor Duty Cycle Commutation PI Controller Speed Actual Figure7 Close
15. lity The PI controller parameters are given to the function over structure Code Listing 1 PI Controller Parameters Struct uword ki Ki Value uword kp Kp Value uword Ymin PI mimimum output value uword Ymax PI maximum output value slong Ibuf j integral Buffer uword PI Output TRL output PI Array The reference value and the actual value are given directly to the PI controller function The values are represented in 1Q15 format Code Listing 2 PI Controller Code using MAC Uword PIControllerSpeed uword PI Parameter uword Actual uword Ref pragma asm MOV R12 MCW Save MCW register MOV MCW 1536 Set saturation and shift left MOV R11 ZEROS Load Zero to RII CoLOAD R11 R10 Load accumulator High with Referenc CoSUB RlIl R9 error reference actual CoSTORE R9 MAS Load error in R9 MOV RL R8 Load Kp value to RI MOV RZ LROT Load Ki value to R2 MOV R3 R8 Load Ymin value to R3 MOV RA R8 MOV Ro R6 Load Integral buffer low value to R5 CoLOAD R5 R8 Load Integral buffer to accumulator CoMAC RZ R9 Yn Ki error Yn CoMIN R11 R4 Limit MAX Yn CoMAX ELIES Limit MIN Yn CoSTORE R6 MAH Store Yn high in R6 CoSTORE R5 MAL Store Yn low in R5 MOV R8 R6 Store R6 in Integral Buffer high MOV R R5 Store R5 in Integral Buffer low CoMUL R1 R9 Kp error CoSHL 6 64 kp error CoADD R5 R6 Y Yn 64 kp erro CoMIN R11 R4 Limit MAX Yn CoMAX RIL R3 Limit MIN Yn CoSTORE R4 MAS St
16. match Timeout occurred the motor will be stopped for protection purposes The ISR Motor Stop function is called during this function 3 8 GPT1 Timer 2 Overflow ISR This interrupt routine will be called every 1mS During the ISR the speed reference value is calculated based on the POT input Application Note 28 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Conclusion 4 Conclusion This application note describes the implementation of the Back EMF Sensorless algorithm for BLDC motors using the Infineon XE164F microcontroller This software solution consumes only very limited CPU resources because of the high performance of the microcontroller and its dedicated peripherals for BLDC motor control 5 Reference XE1666 User s Manual AP16160 XE164 DriveCard Hardware Description Board AP9001 Low Voltage 3phase Inverter with MOSFETs and 6ED driver Hardware Description AP08071 Hardware and Software Description DriveMonitor AP16155 ADC Result Handling on XC2000 XE166 family of Micrcontrollers AP16117 Speed Control of Brushless DC Motor with Hall Sensor Using DAVE Drive for Infineon XC164 CS CM microcontrollers QUII deco INE ES Application Note 29 V1 0 2010 03
17. me and two phases conduct at any given time The commutation timing for Sensorless drive can be calculated by examining the induced EMF across the inactive phase If the zero crossing of the phase back emf is detected then the commutation of the appropriate stator windings is possible Phase A Phase B Phase C AT ompa ompare value AO za i M aie i Cp Compare value ompsre value Compare value 60 120 180 240 300 Electrical Degree Figure 4 Phase Voltage and Induced EMF As shown in Figure 4 the back emf is trapezoidal in shape only two of the 3 phases are seen to conduct at any given time The inverter switching pattern is easily derived from the back emf This switching pattern is organized into 6 commutation states Table 2 Motor Position and Commutation Sequence Position Energized Phase Non Energized Phase 00 A B 600 A C 1200 B C 1800 B A 2400 C A 3000 C B P WOIWUIO Application Note 8 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Principle of Sensorless Operation 2 5 Back EMF Measurement In Block Commutation mode while tvo phases are conducting the neutral voltage is approximately one half of the DC link voltage The relation between phase voltage and back EMF is dl Vp R I L qc Eemf ste 1 2 Where Vp Phase Voltage R Winding Resistance L Winding Inductance Phase Current dildt Rate of change of current
18. mutation function is called and if the motor is running in closed loop Sensorless Mode Speed Ramp up then PI controller and Duty Cycle Update functions are also called T13 Period Match ISR Commutation If CloseLoop PIController Duty Cycle Update Speed Rampup C Return Figure9 Flowchart CCU60 T13 Period Match ISR Application Note 15 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 4 1 Commwutation Function Back EMF detection and commutation are implemented in the Commutation function Once the Motor Start function is called the motor will start to run in Open Loop mode During this phase the commutation speed and the phase voltage are increased continuously until the Back EMF voltage is interpretable The application then switches to the closed loop mode and the motor is accelerated until it reaches the reference speed Open Loop Cose Loop Frequency 2 End Freq AT 7 ee Start Ref Linear e 4 Rampup Quadratic Start Freq Figure 10 Motor Behaviour during Open and Close Loop Application Note 16 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 4 1 1 Open L
19. nasse nasse isses assai assess assa sa ssa sa resa 28 3 8 GPT1 Timer 2 Overflow ISR iii 28 4 076 ullLil 29 5 ASIDE RICE RIT TETTE OE E es 29 Application Note 4 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Introduction 1 Introduction Because of their compact size controllability and high efficiency Brushless Direct Current BLDC motors are used in a diverse range of industries including appliance manufacturing automotive aerospace consumer medical industrial automation equipment and instrumentation BLDC motors do not use brushes for commutation but are electronically commutated instead The BLDC motor is usually operated with rotor position sensors Hall Effect sensors or Encoders since the electrical excitation must be synchronous with the rotor position It is desirable to eliminate position sensors for the reasons of cost reliability and mechanical packaging That makes it more important to control the BLDC motor without the position sensors Sensorless Operation This application notes describes the implementation of a Sensorless control algorithm for BLDC motors using the Infineon XE164F microcontroller The BLDC motor s Back emf is used for commutation In the following chapters the principle of the Sensorless control algorithm and the software implementation is discussed in d
20. nto the CCU61 compare register e Timer T12 should be reset and started again The MCMOUT shadow transfer will happen during the CCU61 compare match event and the next commutation pattern is loaded into the MCMOUT shadow register after the MCMOUT shadow transfer Application Note 19 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation Vdc Phase NOM Voltage Zero Crossing 0 60 120 180 240 300 360 i I Electrical Degree 4 Slope 0 93 Slope1 Slope 0 94 Slope1 Slope 0 93 Slope1 3 Energized ALB A4 C BHC i BHA C A CHB Pise Non f Energized C B A C phe CCU63 Compare Match ADC Sequential Source CCU61 Compare Match Figure 13 BEMF Detection Timing Diagram This function can handle 4 different operation modes Table 5 Motor Operation Modes State Action 1 Open Loop Rampup Phase for BEMF Detection 2 Start of time Between two Zero Crossing 3 Normal Running Mode 4 Turn off Motor Application Note 20 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation Commutation No Yes O Ramp Motor Stop Motor Freq gt Check Freq C Return Read Bemf Value NO C Return Bemf Zero
21. on 1 1 Electrical Revolution Mechanical Revolution Pole Pairs Application Note 6 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Principle of Sensorless Operation Figure 2 Six Step Commutation Sequence 2 3 Three Phase Inverter An inverter is an electronic circuit for converting direct current to alternating current The structure of a typical three phase voltage source power inverter is shown in Figure 3 The six MOSFETSs are controlled by the input PWM signals A A B B C and C that shape the input voltages supplied to the motor terminals Phase Figure3 Three Phase Voltage Source Inverter Note that whenever the MOSFET A is switched on MOSFET A must be switched off and vice versa to prevent damaging shoot through current Table 1 Commutation Sequence PhaseA 0 0 fe 00 p PhaseB TF Od 0 PhaseC Jo e fH 0 A OFF ON B ON OFF C OFF OFF A OFF OFF B OFF OFF C OFF OFF ON ON Application Note T V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Principle of Sensorless Operation 2 4 Sensorless Mode of Operation One of the most commonly used methods for acquiring position information is to monitor the induced EMF of the machine phases when they are not being energized Using the common six step commutation one phase is inactive for 33 33 of the ti
22. on the POT input e Timer 2 is configured in timer mode Count up control e Start Timer2 after initialization e Timer 2 Overflow value is 1 mS After peripheral initialization the motor initialization function is called which initializes motor control specific variables and the motor start function is called to start the motor Application Note 13 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 3 Interrupt Service Routines ISRs In this implementation six ISRs are used to execute motor control specific functions The Interrupt priorities and function calls are listed in the following table Table 3 ISR Priority and Function Call Period Inerrupt Configuration Function Call mu T13 Period Match 50uS Commutation Speed Ramp up PI Controller Duty Cycle Update 2 T13 Compare Match o Selection E CV Measurement 3 T12 Compare Match NN Spee d Calculation on Channel 2 Time 4 T12 Period Match 254mS Motor Stop 5 Cta o booo 2 7 MotoStop 6 GPT1 Timer2 1ms 4 i B 60 Commutation Time 5 HEUuREBLILBILEA inu 922 MotorSpeed RPM PolePair 6 Application Note 14 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 4 CCU60 T13 Period Match ISR This interrupt routine is executed for every 50 us PWM frequency is 20 K The Com
23. oop Mode When the motor is started there will not be any Back EMF It is necessary to control the motor in an open loop configuration until sufficient Back EMF has been generated In this mode the motor is started with a particular speed based on a start frequency value and the initial applied voltage is defined by a start duty cycle value Then the applied voltage and commutation speed are increased based on a voltage increment value and a frequency increment value respectively The voltage increment and frequency increment values need adjustment based on the motor and load conditions If the load is higher then the voltage increment or frequency increment value should be adjusted to drive this load This can be achieved by increasing the voltage increment value or decreasing the frequency increment value Once the motor reaches the speed corresponding to the Back EMF check frequency value the actual Back EMF value is checked If the Back EMF value is interpretable then control Will switch to close loop The actual frequency voltage increment and frequency increment values used in the software are scaled The following equation gives the relationship between actual and target values Frequency T severe sunl Ord Where Frequency T Target Value Frequency A Actual Value I own PWM frequency 20kHz Normalization value Maximum actual value for frequency is around 200 Hz for 20 kHz PWM frequency 128 Freq Increment T Freq
24. ore y high in R4 return register MOV MCW R12 Restore MCW register value Load Ymax value to R4 pragma endasm PI Controller will command a duty cycle value to achieve the required speed The duty cycle value is updated into CCU63 compare register Application Note 26 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 5 T13 Compare Match ISR The T13 Compare Match ISR is executed for every 50us if PWM frequency is 20K During this ISR the channel selection and compare and current measurement functions are also called 3 5 1 Channel Selection Function This function is used to find non energized Phase winding and to select the appropriate ADC channel to measure the induced voltage Channel Selction Y Read MCMOUTL Register Phase A OFF No Assign ADC Channel 0 Phase B OFF No Assign ADC Channel 1 Phase C OFF Assign ADC Channel 2 Return Figure 17 Flow Chart for Channel Selection Function Application Note 2f V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 5 2 Compare amp Current Measurement Function During this function call the motor current value or the DC link voltage value is read from the ADC result register Over current prot
25. over time E Back EMF emf There is no current in the non energized phase so equation 1 2 becomes Vp Eemf a 1 3 This means that by measuring the terminal voltage in the non energized phase the Back EMF is easily determined However the above conclusion is valid only when the two conducting phases are active If one or both of the phases are being chopped then the neutral voltage will vary and the relation between terminal voltage and back emf will not be valid For this reason the terminal voltage measurement should be synchronized with the PWM signal used for chopping This is shown in Figure 5 WE e stop h1 Pos 1 104ms Demagnetization p Spike rase A Bemf Sampling Phase HB CH1 2 00V CH 400 CHS 2 004 M 100 us Figure5 Phase Voltage and ADC Sampling Time Application Note 9 V1 0 2010 03 9 po AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Principle of Sensorless Operation The disadvantage of using the ADC is that it is difficult to achieve a high speed range This is because the ADC sampling is performed only once per PWM cycle Therefore when the motor speed increases the number of PWM cycles per commutation is decreased However to obtain an accurate zero crossing measurement a minimum of approximately 12 PWM periods per commutation are needed This limits Sensorless operation at high speed especially for motors with a large number of poles This prob
26. ster shadow transfer enabled during CCU61 compare match with optional synchronization on T13 zero matches e Trap function is enabled for emergency stop Application Note 12 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Software Implementation 3 2 3 ADC Initilization The ADCO module is used to measure the induced EMF in the non energized phase motor current DC link voltage and the speed reference e The measured induced EMF value of Phase A in channel 0 Phase B in channel 3 and Phase C in channel 9 are stored in result register 3 e Channel 15 is configured to read the DC link voltage and the result is stored in result register 0 e Channel 8 is configured to measure the motor current and the result is stored in result register 0 e Channel 13 is configured to read the speed reference value via POT and the result is stored in result register 1 e Select P5 0 P5 3 P5 9 Channel 0 3 9 as AD channels 10bit conversion time 3 7 us Arbitration Parallel Source for measuring the phase voltages e Select P5 8 P5 13 P5 15 Channel 8 13 15 as AD channels 10 bit sampling at T13 Period match conversion time 3 7 us Arbitration Sequential Source 0 for measuring motor current reference speed and DC link voltage respectively 3 2 4 GPT1 Timer 2 Initilization In the GPT1 Timer 2 overflow Interrupt Service Routine ISR the reference speed value is calculated based
27. ther key application tasks 1 2 Hardware and Software Components The following hardware and software components are required e PC with Microsoft Windows 2000 or above e Infineon XE164F Drive card e Infineon Low Voltage Inverter Board i e Infineon Drive Monitor Stick e BLDC Motor MAXON EC32 15W e 24 V Power supply for Drive Board e KEIL uV3 Tool chain for Infineon XE164F Application Note 5 V1 0 2010 03 9 co AP16173 In fi neon Sensorless Control of BLDC Motor using XE164F Microcontroller Principle of Sensorless Operation 2 Principle of Sensorless Operation This chapter describes the principles of Sensorless Operation 2 1 Motor Theory This application note focuses on control of the most popular and widely used 3 phase BLDC motors The Brushless DC motor consists of a Permanent magnet that rotates surrounded by three equally spaced windings that are fixed Current flowing in each winding produces a magnetic field vector which sums with the fields from the other windings By controlling currents in the three windings a magnetic field of arbitrary direction and magnitude can be produced by the stator Torque is produced by the attraction or repulsion between this net stator field and the magnetic field of the rotor 2 2 Principle of Operation The commutation of a BLDC motor is controlled electronically The stator windings should be energized in a particular sequence to rotate the motor It is important to
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