1 Synopsis 2 Background – What is a robot?
Contents
1. motor could be slowed and reversed from logic level inputs June August 2000 During the summer break researched the computer interface element of the project and came across the Basic Stamp microcontroller manufactured by Parallax Industries More research revealed that this microcontroller could be programmed easily in a form of the Basic programming language and could be configured to any 8 bit configuration of inputs and outputs This seemed like the ideal solution as Parallax had the user manuals and software available to download for free http www parallaxinc com html_files downloads download htm which gave me time to study them and also meant that the robot would become autonomous again It was at this point realised that the discreet stepper motor drive circuit that had built would require too many I O lines and that would need to find a suitable hybrid driver IC for the stepper motors had acquired September 2000 purchased the Stamp module and programming lead from http www tech supplies co uk and tried the initial simple program examples from the user manual October 2000 Enrolled at Huddersfield University and presented initial idea and report for project 17 Design History continued Detailed Design History The initial design specification for the project was that the robot would be controlled by the stamp microcontroller which would receive inputs from photologic sensors and would drive via tw2. robotics info articles linesen linesen htm as the author of the article Kam Leang had included information about interfacing the sensors to a microcontroller and had the code for his non eautonomous pc controlled robot on the web site The sensor module was initially tested by mounting the sensors on prototyping board and once they had been confirmed to be suitable the sensor array was then built on a piece of veroboard suitable for mounting under the robot It was found that the sensors although working in the infra red band were susceptible to interference from ordinary incandescent fluorescent lighting and the solution to this problem was initially overcome by colouring in the cases of the detectors with marker pen although in the finished design this was achieved by painting the cases of the sensors with matt black paint These calculations and circuit are available in the project logbook See appendix for search results See appendix for printout of website 18 Design History continued Detailed Design History continued A convenient chassis was found in the form of a metal psu case obtained from my work This was fitted with the stepper motors at the rear and initially two fixed wheels at the front See picture The robot was fitted with two fixed wheels at the front initially was aware the robot would not turn properly if at all but had no suitable castor skid at that time and wanted to check that the s
3. 2 01 01 03 01 02 03 01 Design History Background The initial idea for the project was thought of during the first few months of the HNC course in 1999 when found out we would be building a year long project in this the second half of the course Dec 1999 The initial idea was to build a robot that would follow a black line using photosensors that would detect the line and alter the amount of power to the motors depending on how much of the line they could see if the sensor saw 90 black and 10 white then the power to the relevant motor would be reduced by 10 if it saw 50 black and 50 white then power would be reduced by 50 etc had actually sketched an initial design and kept it but unfortunately have misplaced it May 2000 discovered that Mark Lupton at Huddersfield Technical College had developed a computer interface that could be programmed via Borland s Turbo C programming language and this seemed an ideal solution for the control of the robot but would mean the robot would not be fully autonomous It also caused a rethink of the sensors due to the fact if the robot was now to computer controlled the sensors had to give logic level outputs Research revealed that optosensors were available that gave logic level outputs During this time built a stepper motor driver control circuit using discreet components for an assignment for Gordon Heys at HTC which thought would use for the robots drive mechanism as the
4. Index Index Synopsis Background What Is a robot Summary of system operation Specification Circuit descriptions Photologic optosensor module Optosensor indicator module Motor driver control module Variable reference voltage source 5V regulated voltage source Microcontroller Microcontroller program code Construction Design history summary Design history Background Detailed design history Discussion of project Conclusion Resources and bibliography Table of figures and drawings Appendices ao fF O N 6 7 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 29 26 2 Synopsis The purpose of this project was to design prototype and build a fully autonomous robot capable of following a pre designated path marked on a surface using insulation tape The robot was to be designed and built to my own specifications A full record of the developmental work was to be kept and provided as evidence of the development of the project The primary objective of this project was to build a line following robot this objective has been achieved and in doing so has provided me with new skills learnt through the development of the project and several valuable learning experiences Background What is a robot A robot may be defined as Robot any automatically operated machine that replaces human effort though it may not resemble human beings in appearance or perform functions in a humanlike manner Robot com
5. Mocs Ve 2 16 _ 19969 10000 Next lowest value l 0 0031 Note The LED s used were special low power types and the green LED requires more drive current to give the same light output as the red LED 9 Circuit descriptions continued Motor driver control module BA6286 LL Z am 12V from battery 5V from voltage regula Fp from microcontrolle Riy from microcontrolle Figure 9 Circuit diagram of motor driver module The motor drive module consists of two of the above circuits based upon the BA6286 motor controller IC with one to control the left hand side motor and one to control the right hand side motor The input output truth table is given below Out Out2 Mode _____ OPEN OPEN Standby Freewheeling b Foward Reverse Brake Table 2 Truth table for motor driver IC The capacitor connected between pin 6 of the device GND and the positive supply is used to decouple the motor power supply to the IC The other capacitors connected to pins 4 and 7 and across the motor are used to eliminate motor noise that could be generated by the motors and fed back into the supply causing problems for logic elements of the circuit Motor speed setting is provided by the variable V per supplied to pin 3 see next page for detailed discussion See appendix for data sheet 10 Circuit descriptions continued Variable reference voltage source LM317LZ Figure 10 Circui
6. e robot is centred on the track both sensors can see the track the output from both detectors will be high and the robot will continue forward 1 1 4 4 Figure 4 Sensor operation lf the robot goes either left or right of the line initially one sensor will see the track and one will not one detector will be high and one will be low the robot will continue forward at this stage Figure 5 Sensor operation Figure 6 Sensor operation Circuit descriptions Photologic optosensor module continued When both sensors cannot see the line the output from both sensors will be low and the robot will then turn in the direction of the last sensor to see the track Figure 7 Sensor operation Circuit descriptions continued Optosensor indicator module 5V Line sensor I P H Track seen L Track not seen ov 0V Green Led Red Led Fixed Sensor Led Fixed Sensor Led I P I P O P I P I P O P H L L H H H H L H L AND gate NOR gate Figure 8 Circuit diagram of optosensor indicator module The LED indicator module consists of two of the above circuits The circuit was designed to aid setting up of the infrared sensor module and to give some visual interest to the robot as it operated The value of the resistor was calculated given Vec 5V Ve 1 6V Ip 2mA for red LED R Voc Me 9 18 _ 47999 16000 Next lowest value l 0 002 Voc 5V Vr 1 6V lIF 3 1mA for greed LED R
7. further development stages had a program that was reasonably confident would work The robot was wired as a system all modules connected but still with no chassis and tested and was found to be working as anticipated A substitute chassis was made with the help of Peter Robinson from the department of design out of ABS This was still flexible but had the advantage of being much easier to work with and had a nice clean finish The chassis was tested by attaching the front castor and rear driving wheels along with the battery this comprised most of the weight and wiring the motors directly to the battery in order to prove that the motors produced enough torque to drive the entire assembly forward which they did The wheels were attached to the motors with a new material called polymorph This material is supplied as granules and is placed in hot water The granules soften and can be formed into a lump which can then be moulded as necessary and becomes hard on cooling This material was used to make a type of woodruff key for the wheels to keep the motor from simply rotating within the shaft of the wheel The modules were then connected on the chassis and the initial testing showed problems that were not immediately obvious during bench testing such as due to the way the motors were mounted that it was necessary for one of the motors to run in the opposite direction to the other The program code was altered and further testing worki
8. mming manual Paralacindusties Version 1 9 Table 5 Books used as reference sources The following Internet sites were used as sources of reference material and ideas www farnell co uk Farnell Electronics rSWWW CO UK RS semiconductors www parallaxinc com Parallax industries http www leang com robotics info articles linesen linesen htm Kam Leang s website www rohm com Rohm semiconductors www onsemi com home Motorola oO o semiconductors www vishay com Vishay optoelectronics www tech supplies co uk Tech Supplies website ee website Table 6 Internet resources 25 Table of figures and drawings S Modified prototype chassis Design history summary 96 Appendix Index of items contained within the appendix Complete Circuit Diagram Basic Stamp Microcontroller FAQ s Program development stages Search results from Yahoo Kam Leangs website Chassis Drawings Data Sheet BA6826 Motor controller IC Data Sheet Optosensors Data Sheet LM317LZ Variable voltage regulator t G G amp amp amp amp 6 97
9. ng revealed that the wheels had not enough grip so elastic bands were fitted around the tire in order to provide more grip The neat wiring of the modules was completed and a trial run revealed further modifications were necessary one of which was to mount the LED s from sensor indicator module on the outside of the box for fault finding purposes Other modifications took the form of solutions to mechanical problems such as the stiffness of the chassis and the rotation of the motor gearboxes due to the steering action of the robot See plans in appendix mo ee Design History continued Detailed Design History continued An unusual fault that appeared at the final testing stage was that the robot kept stopping the robot should be moving in some direction at any given time This was traced back to the fact that the motors were stalling Once the speed was increased the problem disappeared and the robot ran and operated perfectly After the speed had been increased it was noticed that the elastic bands on the wheels proved unnecessary 29 Discussion of project This project has been far more mechanically challenging than electronically challenging for me have had to find innovative solutions to problems had not envisaged when embarked on this project It has also proved to be a valuable learning experience for me even the set back of having to completely redesign the project at the half way stage proved a learning oppo
10. nufactured by Parallax industries The microcontroller receives inputs from a pair of infrared sensors H23LOI manufactured by Vishay and from these inputs determines if the robot should continue forward or the direction that the robot should turn Forward motion is provided by a pair of motor gearbox driving the rear wheels these are driven from a pair of motor driver IC s BA6286 manufactured by Rohm which are controlled from the microcontroller In order for the robot to turn one wheel is stopped while the opposite wheel continues to turn The robot will continue moving forward until neither sensor can see the black line at that time the robot will turn in the direction of the last sensor seen until one of the sensors can again see the line Sensor Output Truth table 0O O I P Next Action 010 Turn O Line not seen 0l1 Forward 1 1 Forward Turn in direction of last sensor seen no Cc gt slooece OOO OOOOOOOC O Turn in direction of last sensor seen no cE Etc Et Figure 2 Control methodology 4 Specification 12V 2 3Ah Sealed lead acid battery Photologic infrared sensors feeding programmable Electronics ae microcontroller controlling DC motors via driver IC s Control method Closed loop control Cost of prototype Approximately 64 in materials Table 1 Specifications of completed project This price includes cost of programming kit for microc
11. o UCN5804B IC s one for each stepper motor The UCN5804 IC s were chosen for their flexibility in choice of driving modes braking reversing ability and their power dissipation Power would be supplied and regulated from a 12V 2 3AH lead acid battery that had been recovered from a redundant lonica telephone system The first stage was to determine the step frequency for the motor control IC s This was achieved by calculating the circumference of the driving wheel estimating a suitable upper and lower speed limit and then calculating the required frequencies A variable frequency pulse generator module was then built to provide the correct range of frequencies required from minimum to maximum After researching data on optosensors found three possible optologic sensors available from Farnell All three sensors had a built in amplifier and gave a logic level output depending on the status of the sensor This would simplify the electronics and make interfacing to the microcontroller simpler The choice was made to purchase the H23LOI FEC327 670 infrared emitter detector pair as these devices were Inexpensive and came as matched pairs to ensure a good level of sensitivity Work was started on the line detection module and when searching on the internet for more information on optosensor interfacing Search engine yahoo co uk search for line sensor found the following website to be a useful source of information http www leang com
12. ontroller 5 Circuit descriptions A complete system circuit diagram is available in the appendix to this report Each individual module is described in detail in this section Photologic optosensor module V out External pull up resistor N 10K CC 5V MEE Voc i 5V i V i 5V Detector i OR 3 INN r Emitter OV OV Figure 3 Circuit diagram of infrared sensor The sensor module consists of two of the above circuits one to detect the left hand side of the line and one to detect the right hand side of the line The current through the infrared emitter is controlled by the series resistor and is approximately 30mA The value of the resistor was calculated given Voc 5V Vr 1 5V IE 30mA from manufacturers data sheet Voo Ve 5 1 5 l 0 03 A 10KQ pull up resistor is required as the detector has a Schmitt trigger open collector output When the sensor cannot see the tape i e the infrared light is being reflected off the white paper the output is logic zero When the sensor sees the tape i e the infrared light is being absorbed by the black tape the output is logic high or 5V The output from the module is fed directly to pins O left hand sensor and 1 right hand sensor on the microcontroller R 116 660 1200 Next highest value See appendix for data sheet Circuit descriptions Photologic optosensor module continued The sensors are aligned so that if th
13. ore the reading of the left sensor GOTO move_forward Continue forward olojo W WININ o0 LET last_left_sensor left_sensor __ _ GOTO move forward a 031 Start of turn procedure Determine 1f the robot needs to turn CE A T Determine 1f the robot needs to turn a e Start of stop_left_motor procedure 038 Send signal to motor driver cct to w o eoor 040 e 04S P rake right motor Table 3 Final program code A Construction The robot is built on a formed ABS chassis with a 360 swivel castor RS 306 4287 at the front and two independently driven rear wheels fitted with 80mm wheels B amp Q VT30 The motors gearbox combination units are fax machine toner unit drive motors part no HO815036 The battery is a Yuasa NP2 3 12 12V 2 3Ah salvaged from an lonica telephone system Figure 18 Key to figures 14 17 Side views e 15 Rear view e 16 Front view e 18 Top view 15 Design History Summary In the table below is a summary of the design stages the robot went through before completion For a more detailed description of the work involved in these stages please refer to the Design History section of this report or the logbook for the project Work done Initial idea for project Obtain information for future use Research parts Rough design outline Purchase microcontroller Present initial design proposal for robot Start initial design of robot Research
14. ote Version 1 robot1 bas was hand written and is available from project logbook ace Circuit descriptions continued Microcontroller Program code IS 5 Comments Robot4 bas Program for basic stamp Command p lt microcontroller written by R Booth HNC Electronics 2001 oOo O o Wo do 004 SYMBOL left_sensor b0 These four lines allow us to define 006 SYMBOL right_sensor b1 more meaningful names to the SYMBOL last_left_sensor b2 variables b0 b3 and therefore make 008 SYMBOL last_right_sensor b3 the program easier to read DIRS 11111000 Set direction of I O pins SoloOl lol o amp BOT Re 1 LET last_left_sensor 1 Assign value to last_left_sensor LET last_right_sensor 0 Assign value to last_right_sensor 015 move_forward Start of forward procedure PINS 01 100000 Send data to I O pins to turn both 017 motor driver ccts on 1 check_sensors Start of check_sensors procedure LET left_sensor PINO Set variable left_sensor equal to NO data on pin 0 NO LET right_sensor PIN2 Set variable right_sensor equal to N NO wINI ol YV oo data on pin 2 O KK IF left_sensor 0 AND right_sensor 0 THEN turn Check to see if any sensor can see the tape if not turn sl YIN oi EO N LET last_right_sensor right_sensor Store the reading of the right sensor 1 LET last_left_sensor left_sensor St
15. parts and additional information Design calculations Research parts Design circult Research parts and additional information Order parts Prototype chassis Further design work Research parts Modify chassis and further research Experiment with optosensors Build and test sensor module oscillator module Prototype and test stepper motor drive module Scrap 1 chassis Complete robot redesign Research parts Prototype then build motor driver module Design and prototype sensor indicator module Modify motor driver module Start building sensor indicator module Complete sensor indicator module Design and build 5V psu Order chassis Initial draft of microcontroller code Modify and compile code Test all modules together Collected previously ordered chassis Made alternate chassis Fit parts to alternate chassis and initial test Modify microcontroller code Start final assembly Continue final assembly Continue final assembly Trial run Modifications Modifications Repairs and modifications Modifications and final test Project finished Table 4 Design history summary Dec 99 May 00 June Aug 00 Sep 00 11 10 00 16 10 00 17 10 00 19 10 00 23 10 00 24 10 00 05 12 00 06 12 00 08 12 00 12 12 00 07 01 01 23 01 01 24 01 01 25 01 01 30 01 01 04 02 01 06 02 01 08 02 01 09 02 01 10 02 01 11 02 01 14 02 01 15 02 01 18 02 01 19 02 01 20 02 01 21 02 01 23 02 01 2 02 01 28 0
16. puter controlled machine that is programmed to move manipulate objects and accomplish work while interacting with its environment Robot any machine which performs physical tasks automatically which would otherwise have been undertaken by a human operative Robots are usually remotely controlled by a computer but some robots have built in computers giving them local intelligence The term robot is derived from the Czech word robota meaning forced labour The modern use of the term comes from the play R U R written in 1920 by the Czech author Karel Capek in which society has become dependent on mechanical workers called robots that are capable of doing any kind of mental or physical work There are many types of robots but the word is most closely associated with a machine that is of humanoid appearance like Honda s Asimo robot show below rth n el Figure 1 Honda s Asimo Robot The building of such a machine costs millions of dollars several years of developmental work and the resources of hundreds of people Britannica online www brittanica com Encarta online www encarta com Newnes Dictionary of Electronics 3 Edition 1997 3 Summary of system operation The project objective was to design and build an autonomous line following robot capable of following a track marked by a black line insulation tape on a white surface The robot is based around the Basic Stamp 1 microcontroller ma
17. rom fax machine toner drive units were tested and found to have a much greater torque this combined with a lighter chassis should enable the overall torque to be sufficient to drive the robot forward The conversion from stepper motor to dc motor made the UCN5804 driver IC s redundant so a replacement was found from the RS catalogue in the form of the BA6286 motor controller RS245 6045 This IC was chosen because of its flexibility in driving braking and reversing capability and it power dissipation The driver itself is supplied from a 5V source and accepts TTL logic level inputs that would come from the microcontroller but is able to source a higher voltage level for the output stages which would be required An external reference voltage applied to the IC determines the high level output voltage setting this feature would be used for speed control of the motors robot The driver circuit was prototyped using a zener diode in order to provide the reference voltage and when finished was connected to the motor gearbox combination and was found to work well The wheels were then fitted to the gearbox and no problem was found with the torque available A low power variable voltage regulator LM317LZ was ordered and a small circuit built in order to provide a variable voltage of between 4 5V and 12V limited by the lower input voltage threshold of the motor driver and the battery voltage This when connected to the Vre input of the motor driver
18. rtunity the most valuable lessons learned are those from your own misunderstandings or mistakes along the way lf the project were to be redesigned at this stage would initiate the following changes to the design The problems with light and alignment of the photosensors would be overcome by using ready built modules these have a fixed sensing distance to overcome the alignment problems are unaffected by external light sources and are available in easily mounted packages Use of a smaller battery the battery chosen for this project was used because it was something already had The use of a selected battery would have reduced the size and weight of the robot and may have been beneficial in terms of improved performance at the expense of decreased battery life Driving wheel choice a wheel with a softer compound tyre would have provided more grip for the driving wheels on uneven surfaces Motor gearbox units these again were salvaged items that were available free of charge but no data on them could be found so calculations were impossible bought in units would have parametric data available for calculations This highlights the problems with salvaged items they are readily available and inexpensive but without the availability of relevant data calculations must be made on atrial and error basis In these circumstances the expense of new items must be considered against the relevance of parametric da
19. t diagram for variable voltage source The LM317LZ is a low power variable voltage regulator The output voltage is given by R 6200 Vara LISV x14 d 2400 With Ry set to its minimum value 6200 V 1 25Vx 1 4 48V OUT MIN a With Ry set to its maximum value 26200 VouTmax 1 25V 1 T 14 90V but since Vij 12V V 12V FNE IN OUT MAX Voutmin is set to approximately 4 48V as this is the recommended Vrefmn for the BA6286 motor driver IC By altering the position of the variable resistor the output of the voltage regulator and therefore Vref is altered this in turn sets the HIGH level output voltage of the driver IC Therefore the voltage and subsequently speed of the motors is adjustable between 4 48V and 12V See data sheet in appendix ae te ee Circuit descriptions continued 5V regulated voltage source 12V from battery 5V to logic circuits 1 LM7805CT 3 2 2400 1000 uF Figure 11 Circuit diagram for 5V PSU The 5V supply is used to provide power for the logic circuits in the robot the microcontroller optosensors indicator module and the driver modules The value of the resistor was calculated given Vec 5V Vr 1 6V IF 15mA Vec V 5 1 6 l 0 015 R 226 670 2400 Next highest value The capacitors are used to provide smoothing and decoupling for the regulator although they are not strictly needed since the regulator is being supplied from a dc so
20. ta Other modifications that could be made are different types of sensors the robot could be made to move towards or away from a light source with the addition of ultrasonic sensors the robot could avoid obstacles with a Hall effect sensor it could detect current carrying conductors etc Line following robots have already found there way into industry with car parts or rolls of paper for the printing industry being carried around the factories on robots that follow a track on the floor 23 Conclusion The primary objective of this project was to build a line following robot this objective has been achieved and in doing so has provided me with new skills learnt through the development of the project and several valuable learning experiences Experiences and skills learnt include Awareness and programming of microcontrollers The different type of motor drive controllers available Use of optoelectronic systems Mechanical difficulties in designing a robot Use of new engineering materials Use of multimedia PC tools during the production of this report have thoroughly enjoyed building this project and have ordered a higher specification microcontroller for my next project 24 Resources and Bibliography The following books were used as sources of reference material and ideas The robot builders bonanza Gordon McComb 99 inexpensive robotics projects Robots androids and animatrons BASIC Stamp progra
21. tepper motors would be powerful enough to drive the chassis forward At this time a message was posted on the Internet newsgroup comp robotics misc in regard to finding a small castor for the front of the robot While waiting for replies to my question a work colleague suggested that use a trackball mouse from a scrap laptop computer that we had at work After modifying the housing slightly this was fitted to the front of the robot see pictures See logbook for details 19 Design History continued Detailed Design History continued Once the variable frequency pulse generator module and the prototyped driver module had been assembled it was possible to test them together by hardwiring the inputs to the driver IC s It was at this point that the major flaw the design was found With the driving wheels lifted off the floor the wheels ran smoothly and speed was adjustable but immediately the robot was placed on the floor the wheels failed to turn When the problem was investigated it was found that it was possible to stop the wheels turning by light finger pressure and since the robot chassis alone weighed 4 32 Kg it would not drive the robot forward The cost of more powerful stepper motors would have been prohibitively expensive so a two stage solution was found in the form of a two dc motors with built on gearboxes sourced from my work and b it was decided to discard the psu chassis because of the weight The motors f
22. urce 12V battery they improve transient response _12 Circuit descriptions continued Microcontroller The Basic Stamp microcontroller module consists of a serial E PROM a PBASIC Parallax BASIC interpreter chip a 5V regulator and a resonator The PBASIC program is stored in the E PROM in a compressed form the program is written on the PC and then complied and sent to the Stamp module via a programming lead which is read Figure 12 from and written to via the interpreter chip The Basic Stamp interpreter chip fetches the instructions one at a microcontroller l time and performs the appropriate operation on the I O pins or the internal registers within the interpreter The Basic Stamp 1 has 8 programmable I O lines holds 80 to 100 instructions and executes an average of 2000 instructions sec www parallaxinc com ov 5V from power supply E OV from power supply OV R av IiE o PCO A PCi ii Iun 2 Left Hand Line Sensor Input 5 Fy Right motor driver Output N C gt i R Right motor driver Output Right Hand Line Sensor is 2 aah F Left motor driver Output i PINS Ry Left motor driver Output PIN4 All other pins left not connected unless otherwise stated Figure 13 Connections to Basic Stamp microcontroller The final version program code for the robot is given on the following page See appendix for data sheet See appendix for previous versions N
23. would allow adjustment of the output voltage and hence speed of the motor As the line sensors were using infrared light it was proving difficult to set them up easily so an indicator module was built to allow you to see on a red and green LED the status of the sensor Initially this was designed to be inside the control box for the robot but later once the robot had been built the LED s were mounted externally so adjustments could be made without having to open the box every time A small 5V psu was built to supply the logic circuits on the microcontroller optosensor module optosensor LED module and the motor driver module 20 Design History continued Detailed Design History continued A simple chassis design in 2mm aluminium for lightness strength and ease of working was drawn up and taken to the mechanical engineering lab where it was found that the only available material was 1mm steel was doubtful whether this would be rigid enough but had it made anyway until a more suitable alternative could be found With all the modules tested and working work could now begin on programming the microcontroller had read and followed a few of the examples from the Basic Stamp manual but this would be my first venture into programming a microcontroller Fortunately with PBasic being a high level programming language the programs are easy to write understand and debug After three attempts one initially on paper and two
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