Project1-Blumann_Claudel_Dechazal_Rimaur
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1. MRCl11 Microcontroller MSCC11 Single Chip Controller Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 23232. Project 1 18 25 int a 0 signal left wheel int b 0 signal right wheel int cas 0 state of the system int casprev 0 previous state of the system bool condition false represents if the state has changed bool slope 2 first front of the signal true rising front int timer 4 starting and stopping clock of each signal initialization functions init analog init function for A D conversion init _ clocktk init function for the clock Acquisition store the data in a and b The PEO pin for signal 1 The PEI pin for signal 2 function for A D conversion of signal 1 and store it in a function for A D conversion of signal 2 and store it in b definition of the slope if test a slope 0 true else slope 0 false if test b slope 1 true else slope 1 false initialization of timer timer 0 0 timer 1 0 timer 2 0 timer 3 0 choice of the case cas choiceofcase a b main loop while true condition cond a b cas while condition Acquisition store the data in a and b The PEO pin for signal 1 The PEI pin for signal 2 function for A D conversion of signal 1 and store it in a function for A D conversion of signal 2 and store it in b condition condition cond a b cas T casprev cas cas choiceofcase a b changecase a b slope timer j Blumann Clau
3. RLEDOS a IRLEDLI A E BSWBMR BSWBMI Eg IELE DOS bs WEN RLEDIO Possibility to put the sensors here We can see that there are enough places beside the wheels on the robot Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 9 25 Available Place We have to put the sensor so that it is able to see the black and white parts of the disk Side view Robot floor The sensor must be here Above view 2 75cm Wheel Axis of the wheel Now the sensor has to be installed You can use glue to fix it on the robot otherwise you can screw it using a bolt Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 10 25 2 3 Connection of the circuit Now we have to find where to connect the different parts of the circuit on the robot 2 3 1 The ground As it is said on page 8 of the MRC11 user s manual the pin 1 on the controller MRC11 is connected to the ground Thus it could be used as a common ground for the circuitry shown before 2 3 2 Getting in the microcontroller As it is described earlier the signal in output of the speed measurer has to be sent in the microcontroller in order to be processed After that the signal goes to the computer which will give us the speed and position information we need The MOTOROLA 68HC11 processor which is on the MRC11 microcontroller of the robot already possess an analog to digital converter so that it is not needed to buy one Here 1s the block diagram of
4. T The first figure can be simplified in the figure below 2 r is the length from one wheel of the robot to the other Geometrically we can deduce all the following lengths 0 l l 2 r d 2 r l b gt L r d tan 0 Z L sin 0 r d Once known the lengths of L and Z it is easy to calculate the new position parameters of the robot By projection we get Xnew Xola L cos P Z sin 0 F Ynew Yoa L sin PF Z cos 0 Prew Yora O Remarks e The lengths can have negative values in the case of a backward movement of the robot for example and one of the two speeds can be nil without changing the equations e Itis clear that if at a time the coordinates X Y are wrong the following positions would be also wrong In fact errors are spread all along the calculations of the positions that is why the position of the robot is only reliable for a certain period of time Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 22 25 4 3 Program written in C The function calcul pos int tl int sensl int t2 int sens2 is called as soon as the sensor has detected the cross of a section of the disc of one of the wheel It is also called if after 500 ms none of the sensor has detected a movement It corresponds at a stop in the movement of the robot The variable tl corresponds at the time taken by the left wheel of the robot to turn of a single section t2 is the same for the right wheel The var
5. Dechazal Rimaur ECE 8873 Project 1 16 25 bool cond int a int b int c This function returns if the switch c f system has changed case 0 return test a amp amp test b break case 1 return test a amp amp test b break case 2 return test a amp amp test b break case 3 return test a amp amp test b break default return true This function makes the differences between changes of cases starting stopping clock void changecase int casprev int cas bool slop 2 int timef4 Variables int result 4 array that contains all information the computer needs bool rot_a 0 sense of rotation for a bool rot_b 0 sense of rotation for b Acquisition store the sense of rotation in rot_a and rot_b the pin PC7 for rot_a the pin PC6 for rot_b Changes of the signal a left wheel if casprev 0 amp amp cas 1 casprev 1 amp amp cas 0 casprev 2 amp amp cas 3 casprev 3 amp amp cas 2 if slop 0 timel0 clock j else time 1 clock result 0 time 1 time 0 Acquisition store the sense of rotation in rot a Acquisition pin PC7 in rot a result 1 rot_a result 2 0 result 3 0 calcul_pos result 0 result 1 result 2 result 3 j Changes of the signal b if casprev 0 amp amp cas 2 casprev 1 amp amp
6. cas 3 casprev 2 amp amp cas 0 casprev 3 amp amp cas 1 if slop 1 time 2 zclock j else time 3 clock result 2 time 3 time 2 Acquisition store the sense of rotation in rot_b Acquisition pin PC6 in rot_b result 3 rot_b Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 17 25 result 0 0 result 1 0 calcul pos result 0 result 1 result 2 result 3 j yn Changes of signals a and b if casprev 0 amp amp cas 3 casprev 1 amp amp cas 2 casprev 2 amp amp cas 1 casprev 3 amp amp cas 0 if slop 0 time 0 zclock j else time 1 clock result 0 time 1 time 0 Acquisition store the sense of rotation in rot_a Acquisition pin PC7 in rot a result 3 rot_a j if slop 1 time 2 clock j else time 3 clock result 2 time 3 time 2 Acquisition store the sense of rotation in rot_b Acquisition pin PC6 in rot_b result 3 rot_b j if slop 0 if slop 1 calcul_pos result 0 result 1 result 2 result 3 J elsef result 2 0 result 3 0 calcul pos result 0 result 1 result 2 result 3 T j else if slop 1 result 0 0 result 1 0 calcul pos result 0 result 1 result 2 result 3 y J Be o void main definition Blumann Claudel Dechazal Rimaur ECE 8873
7. v1 v2 2 value in cm ms j else X X I1 cos phi value in cm Y Y 12 sin phi value in cm phi phi value in radian initialisation of the global variables nb_t1 0 nb_t2 0 totall 0 total2 0 j 4 4 Conclusion e We thought that it was interesting to make a mean value of the speed of each wheel to reduce the risk of calculating a wrong position Indeed since we calculate a position thanks to the previous one a wrong position would provoke an error for all the following ones e Itis difficult to evaluate the time taken by the embedded computer to perform the programs In case it would be quick enough we could increase the number of measures taken by our sensor and by the way the precision and if it is too slow we could decrease the number of measures e We do not know well the library including in the computer For example we are not sure that the computer is able to calculate sinus or tangent of an angle directly If not so we would have to make approximations like sin 0 0 Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 24 25 o Bibliography 1 Honey Well HOA0708 0709 Reflective Sensor Datasheet 2 HoneyWell HOA1180 Reflective Sensor Datasheet 3 ST GENERAL PURPOSE DUAL JFET OP AMPS Datasheet 4 NEOHM GENERAL PURPOSE CARBON RESISTANCE Datasheet 5 www farnell com 6 www radiospares fr 7 Mekatronix manual on www mekatronix com Talrik Assembly Manual Talrik M User s Manual
8. Blumann Etienne Claudel Guillaume Dechazal Olivier Rimaur Fabien January 2003 ECE8873 Computing Techniques of Control Systems Project 1 Measurement of position and speed of the Talrik II robot Index 1 ELECTRONIC ASPECT 4 1 1 Principle 4 1 2 Components used and implementation 6 1 2 1 Reflective sensor 6 1 2 2 Amplification 6 1 3 Design 7 1 4 Price of electronics components 7 2 MECHANICAL ASPECT 8 2 1 Disk made 8 2a Position of elements HOA0708 8 2 3 Connection of the circuit 11 2 3 1 The ground 11 2 3 2 Getting in the microcontroller 11 3 ALGORITHM FOR DETERMINING THE POSITION AND VELOCITY FROM THE ENCODER MEASUREMENTS 13 3 1 A one wheel system 13 3 1 1 Different methods to determine the position and velocity of a one wheel system 13 3 1 2 Choice of the algorithm 14 3 1 3 The chosen algorithm in detail 15 3 2 A two wheel system 16 3 2 1 The differences between a one wheel and a two wheels system 16 3 2 2 The chosen algorithm 16 4 ALGORITHM TO DETERMINE THE POSITION AND THE VELOCITY OF THE ROBOT 20 4 1 Speed 20 4 2 Position 20 4 2 1 The two wheels turn at the same speed V1 V2 21 4 22 _ The two wheels do not turn at the same speed the robot has a rotation movement 21 4 3 Program written in C 23 4 4 Conclusion 24 5 BIBLIOGRAPHY 25 Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 INTRODUCTION The goal of this project is to design an encoder to determine the position and the veloci
9. del Dechazal Rimaur ECE 8873 Project 1 19 25 4 Algorithm to determine the position and the velocity of the robot 4 1 Speed Once known the time t taken by each wheel 1 to turn of a single section we can easily calculate the speed of rotation 0 9 a ti Time ti Then we can calculate the rectilinear speed of the robot for each wheel 1 VicR 90 with R the radius of the wheel V gt R 0 gt Vi Vrobotz V 1 V gt 2 V2 4 2 Position To represent the position of the robot we use three parameters e 2 coordinates X Y to represent the robot in the plan e angle to give its direction in comparison with the axe X The scheme beneath represents the coordinates of the robot We can differentiate two cases for computing the position of the robot Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 20 25 4 2 1 The two wheels turn at the same speed V1 V2 The robot has a rectilinear movement During the time T it has move of the folowing way X new X old V1 T cos F Ynew Yoa V1 T sin F new Vota 4 2 2 The two wheels do not turn at the same speed the robot has a rotation movement The figure beneath represents the movement of the robot from the point X Y and the different parameters that we consider to calculate the next position Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 21 25 For a brief period T we can approximate that l V T and l2 V2
10. en another function calculates the position and velocity of the machine But as the robot has two wheels this algorithm must have an interest in the different cases can occurs at the start The right and left sensors detect white marks The right and left sensors detect black marks The right sensor detects a white mark and the other a black one The right sensor detects a black mark and the other a white one And the system must manage the possibility a wheel can turn whereas the other is immobile And so a side can not be specified regarding the other The algorithm must be totally symmetric 3 2 2 The chosen algorithm The final algorithm to determine the rotation frequency is written in C because downloading C on the robot is easy The functions have been created to be executed very fast only logical operations include lt libscrtk h gt library taken from mekatronix web site that includes functions regarding conversion and the clock bool test int a This function tests if le signal a is under int threshold 128 the threshold Middle of the scale 0 255 bits return a lt threshold int choiceofcase int a int b This function gets the case where if test a amp amp test b return cas 0 the system is if test a amp amp test b return cas 1 if test a amp amp test b return cas 2 if test a amp amp test b return cas 3 ar Blumann Claudel
11. g data in a variable port PEO and call function to A D conversion Detecting if the signal is under the threshold determine if the sensor is in front of a black or a white mark e Determining if the emission must be in a rising front or a descending front Example Start clock Stop clock and emission C Ee YW cst Threshold Program clock start and stop e Waiting for an exceeding of the threshold sense 2 e Reset clock e In an infinite loop O O O O OO sO Waiting for an exceeding of the threshold sense 1 Stopping the clock and storing it Reset clock Call calcul pos function with the registered clock and the sense of rotation Waiting for an exceeding of the threshold sense 2 Stopping the clock and storing it Reset clock Call calcul pos function with the registered clock and the sense of rotation Thus the maximum of accuracy 1s obtained because this algorithm detects the half period of the signal it makes a difference between the white and black marks Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 15 25 3 2 A two wheel system But Talrik II has two wheels and two different motors So the system is more complex We will comment here these differences and the final algorithm 3 2 1 The differences between a one wheel and a two wheels system The main idea of the algorithm does not change the determination of the frequency of the signal is still done on the robot and th
12. iable sensl has the value 0 when the movement of rotation of the left wheel 1s forward and 1 when the movement of rotation is backward definition of constants define R 7 24 radius of a wheel of the robot in cm define r 9 48 half length from a wheel of the robot to the other one in cm define nb_sections 12 number of sections on the wheel variables global nb tl nb t2 totall total2 phi X Y void calcul_pos int tl int sens1 int t2 int sens2 4 definition of variables int V1 0 V2 0 teta d L 11 12 z stop 0 if t1 t2 0 stop condition if the sensor does not get data after 500ms t1 t2 0 stop 1 j else if sens 1 1 tl tl j if sens2 1 t2 t2 j if tl 0 nb tl totallztotall tl i if t2 0 nb t2 total2 total2 t2 j Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 23 25 if nb_tl nb_t2 gt 2 stop data are updated every 3 measures to have a mean value except if the stop condition happens 11 2 II R nb tl nb sections v1 ll totall 12 2 1I R nb_t2 nb section v2 12 total2 computing of intermediate variables if vl v2 0 see above the explanations for geometric calculations teta L1 12 2 r d 2 r 12 11 12 l r d tan teta z l sin teta r d computing of position and speed variables X X 1 cos phi z sin teta phi Y Y 1 sin phi z cos teta phi phi phi teta Vrobot
13. n alimentation will be done with a 5V supply voltage and throw a 220Q resistance For the HOA1180 003 the output current is about 2mA The thought a 470Q resistance the output voltage of this unit is about 0 94V For the HOA0708 001 the output current is about 0 2mA The thought a 4 7kQ resistance the output voltage of this unit is about 0 94V 1 2 2 Amplification The microcontroller works in TTL voltage Then if the input voltage is smaller the 5V there is a lack of information Thus we must amplify the out signal of the optical unit The gain is calculated for having a maximum 5V voltage Then G 5 3 Amplification will have a gain close to 5 Components used for this operation are operational amplifier TL082 This component is composed by two JFET operational amplifiers The first will be used for amplification about 4 6 and the second will be used for having a positive amplification Thus its gain will be 1 Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 6 25 1 3 Design This scheme was made with Orcad Spice and use E12 series for resistances U1 ground 2 R1 any R3 1 U2B R5 TLO82 220 HOA 1180 003 7 V_ampli Supply 5 i V1 5vde ground 1 4 Price of electronics components The choice of the sensor will depend on the mechanical aspect In fact the advantage of the HOA1180 is that it can works with a distance between sensor and reflective area of 12 7mm The HOA0708 works
14. needs only one reflective sensor Thus the system is easier to study Anyway we notice there are several methods to determine the position and velocity of the robot 3 1 1 Different methods to determine the position and velocity of a one wheel system The system to determine the position and the velocity of the robot is not very complicated we can divide it in two parts The first one gives the frequency of rotation of the wheel and so the speed of the robot The second one calculates the position of the robot Signal from Rotation Speed and Block 1 Block 2 the captor frequency position Simple schema of the algorithm As the signal from the captor is continuous the blocks have to work with a continuous data flow Therefore both part of this system have to treat quickly the data faster than the rotation frequency of marks Here the rotation frequency of marks is the rotation frequency of the wheel multiplied by the number of black marks Reflective wheel Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 13 25 One solution to make the system quicker is to execute the two parts with different chips For example the block 1 can be on the robot and the second block on the computer with a wireless connexion 900 MHz Another solution is to make two processes which are executed on the same chip Thus there is no need of any wireless connexions But as all the calculi are worked out by the same microcontroller
15. the chip has to be strong enough to maintain the real time The last solution is to execute the two blocks one after the others on the same chip and so not to have two processes This idea is the most simple to understand and to program but needs more calculi power So each solution has its advantages and its disadvantages but for our problem one of them is better than the others 3 1 2 Choice of the algorithm We have chosen the third solution Indeed it seems to be the best one because of several reasons e A radio connexion is not required we do not need to manage the transmission e Even if the calculi are quite big we do not saturate the microcontroller because there is not a big data flow the maximal speed of the robot is 12 inches per second Time t and distance d k gt Relation between rotation frequency and signal frequency In the schema above d determines the distance covered by the robot during t seconds Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 14 25 3 1 3 The chosen algorithm in detail To well understand the system we will develop the second block later Here we keep an interest on the first block that has to determine the period of time where a mark black or white one is in front of the sensor We can resume it in few lines e First converting the signal from the reflective sensor to digital with the analogue to digital encoder embedded in the microcontroller Then storin
16. the processor Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 11 25 MODAS MODB Von Yas E axXDuT XTA EXTA IRO XRG RESET UR Ysw OSCILLATOR LLATOR INTERRUPT line PULSE PAT PAVOCT ACCUMULATOR E ERTER PAG PA TIMER PAd SYSTEM PA3 PA2 PA a PAO PERIODIC INTERRUPT 1024 BYTES STATIC RAM ADDRESS BUS M3 fT COM yr Ea As we can see the analog to digital converter inputs are the PEO to PE7 ports and we have to send 2 voltages Vrh high level and Vrl low level we can choose it equal to the ground The corresponding ports on the MRC11 microcontroller are given on page 8 and 9 of the MRC11 user s manual PEO to PE7 corresponds to pin 43 to 50 Vrl and Vrh correspond respectively to pin 51 and 52 2 6 10 14 JB 22 26 30 34 38 42 46 DD 54 5B t t t to ttt st owo 8 3 8 o OU Jll l 0 PS HGH HHH ee Bee ce ee H 1 5 3 33 17 2 25 23 33 37 41 43 49 53 5 Thus we can connect pin 51 to pin 1 gnd Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 12 25 3 Algorithm for determining the position and velocity from the encoder measurements So as to simplify the problem we will consider firstly a system with only one wheel In the second part we will have an interest for two wheel systems Finally we will comment on the calculus of the position and the velocity of the robot 3 1 A one wheel system As this system has only one wheel it
17. ty of the TalrikII robot In this report it will treat about electronic aspect mechanical aspect and programming aspect Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 3 25 1 Electronic aspect 1 1 Principle Wheel Microcontroller The reflective sensor is an infrared emitted system that functions on reflection of the infrared light on a sensitive surface Then reflective elements must be placed on wheels Wheel No reflective area Reflective area The reflective areas can be done with aluminum materials The no reflective areas can be bone with black materials With this type of system and a reflective sensor we can detect the presence or not of a reflective or not areas Thus in having the length of these areas we can know the angular speed of the wheel Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 4 25 Reflective sensor Reflective area Reflective sensor No reflective area Then the output current will be in a high level if the area is reflective and in a low level if not Thus trough a resistance we have the following voltage signal High level Low level No reflective area Reflective area Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 523 1 2 Components used and implementation 1 2 1 Reflective sensor Two different sensors can be used e The reflective sensor HoneyWell HOA11 0 003 e And the HoneyWell HOA0708 001 These input current drives are about 20mA The
18. with a maximum distance of 3 8mm Nevertheless the HOA1180 is more expensive Constructor Reference Furnisher Price HOA0708 001 Ze CFR 2200 0 34 CFR 1 2kO 0 34 NeOhm CFR 470Q or Radiospares 0 34 CRF 4 7kO CFR 5 6kO 0 34 The total price is 22 51 with the HOA1180 and 8 08 with the HOA070s Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 7 25 2 Mechanical aspect 2 1 Disk made The radius of the wheel is given and equal to 3 81cm In this section we will make specifications about the reflective disk behind the wheel A restrain 1s that this disk must be easy to build Thus dimensions should be human With this disposition the state change of the sensor will be done every 30 in other word every 30 2 75 1 43cm Then maximum precision will be 1 43cm 2 2 Position of elements HOA0708 2 2 1 The sensor As we said the maximum distance from the disk to the sensor is about 3 80mm ANODE 7 CATHODE 5 i a EMETTEUR 8 COLLECTEUR m Blumann Claudel Dechazal Rimaur ECE 8873 Project 1 8 25 Then disposition of elements could be the following Sensor After observing the robot we can place the sensors like this BS WFM ELED RLE DGS BSWFMI M BSWFMR IFU Em Tor E M IRLEDOZ a NCDSI 2 EMI h IRDEMR NCDSL NECDSR ECDSIL ECDSA ECDSER On Sensor Head iy wheel IRLEDI2 BS WRR o o 7 TRYEM o
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