Projekt Raport z budowy robota na zawody The Freescale Cup 2012
Contents
1. Written software allowed car s speed and each PID regulator term s gain to be changed wirelessly using PC 3 3 Motor Control Board Motor Control Board MCB provided by freescale includes two H bridges MC33931 two LM2940 5V regulators one for servo supply and one for logic supply The motor control board has been modificated in order to allow braking The IN1 pins of left and right H bridge were desoldered form the GND lifted up and connected to MCU pins PA14 and PA15 which were set as output in order to enable braking by setting IN1 and IN2 High Braking distance was decreased from over 3m to under 1m DR JA Figure 5 Modded MCB 3 4 Monitoring the battery To monitor the battery a 1 2 voltage divider has been used Divided voltage is measured by analog digital converter of the microcontroller 3 5 Encoders To achieve the same speed regardless of voltage on the discharging battery an AS5040 magnetic rotary encoder was mounted near the each motor s rotor 2x6mm round magnets were glued to each rotor in order to provide magnetic field rotation to the encoders when driving The software PID regulator controls the motors PWM to achieve the desired rotational speed which allowed to maintain the same performance of the software regulator used to follow the line regardless of battery voltage Figure 6 Encoder s connection diagram 3 6 Camera The TSL1401R LF camera provided by Freescale was used to deter2. Two pieces of an office ruler which are attached to the chassis with screws hold it The camera needs an extra light which also has been provided A piece of PCB containing LEDs is attached to the rulers below the camera It is 280mm wide wr EGEL WO SHH KEE H Figure 3 Headlights of the car 3 Electronics Control circuit of the car is divided amongst two boards both provided by Freescale 3 1 MCU Board The TRK MPC5604b board was provided by Freescale and has not been modified in any way The board didn t contain MAX232 driver receiver so on board Virtual Serial Port was connected to processor s SCI RXD TXD and USB port was used to receive serial transmission Later when bluetooth module was added Virtual Serial Port was redundant 700 mil O s R 99 O o k3 ES ESS Ze lt gt ases Ee SS E lt gt m oo L ZE odes freescale oo bag BB us sem ap o JS O os EIE Jo ke D PUR H oo oo zott oo ES OO on 5a Ne pup VE EN D vert ggr EE Cla LEI qn qu VD r sal ER O OO OO OO O co si s2 s3 DI uO mmm co oo LINLRXD ro Gr 8 Er 322 a cc Fe 1P4 29 K 4 300 mi le Figure 4 MCU board s schematic pin outs and size 3 2 Bluetooth module In order to better understand behavior of the car and to debug it easily a bluetooth module has been used It provided wireless communication between PC and microcontrol ler in distance around 10m
3. STEROWNIKI ROBOTOW PROJEKT RAPORT Z BUDOWY ROBOTA NA ZAWODY THE FREESCALE CUP 2012 Autorzy Przemys aw Jankowski Przemys aw Kocha ski Wroc aw 2012 Table of contents 1 Introduction 2 2 Mechanics 3 24 ONASSIS e E ee ee ASS SY WAW A A AS 3 22 BOA Ys e Meng SY Ser np hee WTZ KET as the Ae Ee EE 4 2 3 Camera and headlights ADA AWA AEK A 4 3 Electronics 4 lo MOU Dodd AN EK BASY EA A 4 3 2 Bluetooth module 4 tos Ata dT AG AW ASA a dA U nod amp Be EEN 6 3 3 Motor Control Board a z a Z BO Z OD neh Ag a 6 3 4 Monitoring the battery aaa Wr M AA 6 SEENEN e 3 6 EE EE 7 3 7 Additional lighting cc eu ae ied Re BON WO BONE W A MRS ARR Bej 3 8 3 8 Electrical noise suppression d aa de dep a ee a 9 39 Power CONSUMP HOM re Re Book RO 6 eg 6 EO aS 9 4 Software 10 4 1 Following the line e soe hele dee Sieger det ee Bee eg ae E 10 4 2 Speed control system e tata BATE eRe Cw Bee EE Rode 10 REENEN 10 4 4 Differential control of motors aa do paw E ee ee a ae aS 11 4 5 Automatic light calibration do da de ERA Re EE ES 11 5 Summary 12 Bibliography 12 Team name A whole lot of left handed space monkeys with razor sharp teeth and unpleasant attitude Team members Przemys aw Kocha ski Maciej Mucha Przemys aw Jankowski Car s name Johnny Figure 1 Johnny the autonomous car 1 Introduction Johnny is an autonomous line following car which was made for Freescale Cup 2012 The goal of a robot d
4. era pixels integration time constantly It allows the car to drive independently of external light conditions and maximize frequency of line position measurements 11 5 Summary After a few weeks of work a well operating and fast robot has come to being It is able to follow the line accurately even on high speed which proves the correctness of the algorithm Johnny managed to end the Freescale Cup 2012 on the third place Although some problems occurred creating a robot provided the constructors a lot of satisfaction and knowledge The work on the robot isn t over though The next step is to increase its speed even more and to create reliable body for the car in order to protect its components and to improve its design Bibliography H Francisco Ramirez Fuentes Marco Trujillo Cuauhtli Padilla Rodrigo Mendoza Using Parallax TSL1401 DB Linescan Camera Module for line detection Freescale Semicon ductor Document Number MPC5604B Rev 0 01 2011 Freescale Semiconductor The Freescale Cup 2011 2012 Season Rules EMEA Release date 03May2011 Freescale Semiconductor MC33931 5 0 A Throttle Control H bridge Document Num ber MC33931 Rev 2 0 12 2008 TAOS inc TSL1401CL 128 x 1 Linear Sensor Array With Hold TAOS136 July 2011 The Freescale Cup wiki http thefreescalecup wikidot com Freescale Semiconductor MPC5604B C Microcontroller Reference Manual MPC5604BCRM Rev 8 5 May 2011 Freescale Semic
5. mine the line po sition It has the resolution of 128 x 1 pixels By setting a CLK signal low and then high next pixel s analog value 2 5V is send to MCU s ADCO The more light each pixel receives the higher the voltage is Process repeats until all pixels are read Figure 7 Mounted encoder s PCB 3 7 Additional lighting Extra light was required in order to achieve high contrast of area seen by the camera It has been provided by an array of 37 LEDs attached to the front of the car Each LED has a 20 degrees of lighting angle and consumes 30mA LEDs are powered from 5V 2A 78805 voltage regulator Although adding the LEDs has increased the power consumption by over 1 1A camera s exposure time could have been reduced over 6 times AN AA Ah Ah ZA EN EN EN EN EN EN le olle elle zle alle lle sfe efe f Ju el A A A A A A A A AA AA We Me Me Figure 8 Headlights connection diagram 3 8 Electrical noise suppression Due to poor design of Motor Control Board especially analog camera signal and GDN going through the same board as high motor current ADO signal from camera was receving strong interference In order to suppress it two 100nF capacitors were added to each motor One side of each capacitor was soldered to one of the motor s terminal and other side was soldered to the motor s case as shown on the picture below Additional 100nF capacitor was added parallel between camera
6. onductor MPC5500 6 MPC5600 Simple Cookbook AN2865 Rev 4 04 2010 PE micro TRK MPC5604B EVB User Manual 2010 P amp E Microcomputer Systems 12
7. owed precise speed control PD speed regulator was needed in order to achieve it Signals from encoders are sent to MCU counter and from there as negative feedback loop to software PD regulator Proportional ie Desired Derivative Speed EA a Fe meto A pulse encoder pulse er lencoder Figure 10 Speed control system 4 3 Debuging A dedicated C application has been developed in order to debug the robot s algorithm using PC It receives data from car through bluetooth and shows such informations like 10 current error and regulator s settings It also allows to tune the regulator and change robot s speed on line This was not used during the tournament though because the robot had to be completely autonomous AR ee A S gt SE S SS Samples 36362 Save Speed 300 P 8 Res 0 l 65535 Delay 0 u Increment 10 D 0 Y Headlights Save a Port COM10 X Close Figure 11 Screenshot from the described application 4 4 Differential control of motors In the first version of a car prototype both motors speeds were always equal and the front axis inclination was the only way to turn Since it was not sufficient at high speed an improvement had to be developed Present version of software allows robot to set different speed on each motor which helps at sharp turns 4 5 Automatic light calibration Automatic software calibration which bases on current light level changes the cam
8. s VCC and GND for further noise filtering Provided filters eliminated all electrical noise Figure 9 Noise reducing capacitors 3 9 Power consumption Adding headlights to a car increased power consumption significantly Every single LED needs 30mA and there are 37 of them so 1 1A current on 5V is needed That makes 5 5W of power used only for LEDs It makes the battery voltage decreasing quite fast Additionally the battery has been once discharged below the level of safety The voltage fell to under 5V which reduced the battery capacity and resulted in even more rapid discharge Car s engines and logic power consumption without lights when driving is 0 7A on 8V that gives 5 6W Total power consumption is about 11 1 W 4 Software 4 1 Following the line A provided 1D camera is the only sensor installed It allows robot to follow the line After acquiring data from the camera a derivative is calculated Then rising and falling edges of the function are being found the biggest represent the edges of the black line Every single pixel has its weight which is a base of calculating error Robot has a PD regulator algorithm implemented which calculates control This causes appropriate front axis inclination By changing gains of proportional and differential terms tuning the regulator and matching them to desired speed and route conditions stable line following can be achieved 4 2 Speed control system Installed encoders all
9. uring tournament is to ride along the black line towards the finishing line in the shortest possible time The obstacles like tunnels elevations and unevenness of the road may occur and the car has to be ready for them Robot has to be completely autonomous and has to stop after completing two laps Johnny was built by three students of Wroclaw University of Technology The construction is based on parts provided by Freescale 2 Mechanics Johnny is a simple model of a car It has one driving axis both rear wheels can be controlled separately though thanks to two DC motors and one turning axis It consists of 3 main sections chassis body and a grip holding camera and headlights 2 1 Chassis Mechanical design of the robot is based on stock plastic chassis provided by Freescale It is 285mm long and 160mm wide There are two DC motors located at the rear section of the chassis They propel the wheels using simple gear system On the middle of the chassis a Ni MH battery is situated ensuring that the center of mass is situated low There is also one servo located on the front section of the chassis right behind the bumper It is responsible for turning front wheels Figure 2 Provided chassis 2 2 Body A rectangular piece of plexiglass 185x130x3mm has been added to hold the MCU board and motor control board All of these parts are the body of the car 2 3 Camera and headlights Camera is located 200mm above the ground
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