Project1_Piednoir_Perrin_Lemarchand_Izaac
Contents
1. Georgia Tech Lorraine School of ECE January the 24 2003 ECE 8873 Project 1 Dr HECK Marie Laure PIEDNOIR Nicolas PERRIN Ronan LEMARCHAND J r me IZAAC IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot Abstract The Talrik II robot has two motorized wheels and a third one which follows the move of the two others When we want the robot to go straight forward or straight backward we need to apply exactly the same command to the two motors and when we want it to turn on the right or on the left we have to make a wheel turn faster than the other This is really simple in theory but in facts we cannot always be sure of what we send to the motors and more important how they react In order to automate the motion we need a feedback this means that we have to know at each time the angular speed of each motor to control if the robot follows the desired path That is the reason why we decided to add two coders on the motorized wheels Each coder after being mounted on the axis of each motor and wheel sends a signal that can be measured and computed by the micro controller in order to find the speed at which each wheel rotates This report will explain which encoders and encoding wheels will be mounted on the Talrik II robot the way to fix them to the axes and to make them communicate to the Motherboard of our robot and an explanation on how2. a source light is present on a side of the wheel and a photodiode is on the other side The logical level of the electrical signal changes if the photodiode receives light or not When the wheel rotates holes and solid parts pass between the photodiode and the light source The signal emitted by the photodiode switches between high and low logic level time Assuming the wheel rotates in only one way the measure of the rotation done by the wheel can be deduced by counting the number of state s changes of the signal ECE 8873 Georgia Tech Lorraine School of ECE _4 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot Assuming the wheel has a constant speed the speed can be deduced by measuring the frequency of the signal s fundamental The previous paragraph has shown how the position and the speed of a one way rotating wheel can be measured Now we will explain how the direction of the wheel can be measured A second device light source photodiode is added but shifted in space Therefore the signal it emits is shifted in time oS oe So the second signal is out of phase by 90 degrees or 90 degrees depending on the way the wheel is rotating ECE 8873 Georgia Tech Lorraine School of ECE _5 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot Direct way the
3. 7kQ 4 10 resistors one 6 wire C2325 communication ribbon a6 AA NiCd battery pack ECE 8873 Georgia Tech Lorraine School of ECE oe IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot If we choose to order non assembled MSCC11 we should make sure we also have the following material as quoted in MSCC11 assembly manual posted on MEKATRONIX s website Soldering iron 60 40 rosin core 0 032 diameter electronics solder Small diagonal cutters for cutting wire and headers Needle nose pliers Wire stripers Hot glue gun and hot glue Masking tape D Interfacing the encoders with the robot 1 Interface board MSCCI1I1 with the robot e Communicate with the MRC processor board MSCCI11 additional board needs to be linked to MRC11 processor board to communicate with the main program and send it data from the 2 encoders As said before MSCC11 communicates with MRC11 through Serial Peripherical Interface SPI or Serial Communications Interface SCI via a 6 wire C2325 MEKATRONIX ribbon We decide to make them communicate via SCI The ribbon should connect J54 plug on MSCC11 board to SCI jumper on MRC11 The ribbon can be purchased on www mrrobot com assembled or not ECE 8873 Georgia Tech Lorraine School of ECE 99 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik
4. Differential Encoders for the Talrik Il Robot Also when needed up to 2 sensor expansion boards MSCC11 can be mounted on the robot Each board comes with 8 analog I O channels and 8 digital inputs It communicates with MRC11 board via Serial Peripheral Interface or Serial Communications Interface MSCCI11 board provides the following information Each digital input is made of 3 pins one Vcc pin one signal pin and one ground pin where Vcc SV C Solution Now we are going to see if the constraints of the encoders are compliant with the robot s ones As we use 2 encoders we need 4 digital inputs on the robot A and B channel from first sensor A and B channels from second sensor But the robot initially has only 2 digital inputs on MRSXO01 expansion board as explained previously Thus we need to add one expansion board MSCC11 on the robot These digital inputs fit the 5V Vcc requirements Regarding the ordering of MSCC11 board there are 2 possibilities Buy non assembled board price 30 Or buy already assembled board price 66 Also as we use 2 encoders we need 2 3 6 2 7 KQ 10 pull up resistors These can be ordered at Farnell We also need some material to mount MSCC11 board a 6 wire C2325 ribbon connect it to the robot and a 6 AA NiCd battery pack to power it up To sum up we need the following to interface encoders with the robot One additional MSCC11 sensor expansion board 30 or 60 62
5. the robot by analysing electrical constraints through documentation of MEKATRONIX robot and boards We made an estimation of material costs Finally we developed the algorithm to compute the position and the speed of the robot The resulting documentation provides an ordering list of needed parts including prices and where to buy them detailed explanations on how to mount the encoders on the wheels and how to interface them with the robot a detailed description of the algorithm to compute the position and the speed of the robot an attached file Talrik exe a video sequence showing the assembly procedure of the encoder on the robot as described in part III above To run the video double click the file This video was modelled and rendered using LightWave3D and compressed into a stand alone EXE file with BINK VIDEO The distances used to model the parts are the real ones the schemes of the part II can be used to build the device ECE 8873 Georgia Tech Lorraine School of ECE _ 30 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot References Robot s website www mekatronix com Talrik II s assembly manual http www mekatronix com manuals talrik tam pdf Talrik II s user manual http www mekatronix com manuals talrik tum pdf MSCC11 assembly manual http www mekatronix com manuals PCB mscc 1 lam pdf MRSX01 expansion board
6. type of wheel chosen the number of ticks per rotation varies between 256 and 2 000 and the maximal frequency accepted by the encoder is about 100 kHz which means that it is able to count a speed between 100 000 2 000 50 and 100 000 256 290 rotations in a second The diameter of the robot wheel is 7 4 cm mt 7 4 50 1162 cm sec 11 62 m sec and 1 7 4 290 6741 cm sec 67 m sec These maximal speeds are pretty high for a robot such as the Talrik II We need to use this values in order to set the frequency on which the micro controller will check what happens in the encoder In order to check if a tick has appeared we should check with the micro controller at a frequency which 1s at least twice as high as the encoder s one if possible Current D Uy SSS ee ee OO Oe Oe a a a D by cc ce cc ce ee ee eee ee cee oe amp 0 0 l 1 Time In red impulses or ticks in the encoder In black instants when the micro controller checks ECE 8873 Georgia Tech Lorraine School of ECE 24 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot We can see that at this frequency when the value measured by the controller changes it means that a tick has appeared The number of ticks is the total number of changes in the values measured by the micro controller divided by 2 A good way should be to create a secondary module who
7. 3 67S Farnell 3 way optical encoder euros 23 6719 ECE 8873 Georgia Tech Lorraine School of ECE 28 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot About In Cora 2 supermarket or Castorama 1 Piece of wood for the ADOUTL O base 25 E Total exc 66 3259 VAT in OTAL poOso2 S REQUESTED DELIVERY B REQUESTED DELIVERY TIME REST NOT DELIVERED As some parts are ordered on French sites and others on American ones we converted euros prices in dollars with a ratio of 1 1 055 Euro We assumed that material such as glue screws and bolts are available in the laboratory Resistors are ordered in 50 quantity as it is not possible to buy smaller packs We ordered non assembled MSCC11 board and C2325 ribbon Both are available assembled The total with assembled MSCC11 and C2325 is 107 32 Also there may be some additional costs due to shipping charges and VAT ECE 8873 Georgia Tech Lorraine School of ECE _ 29 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot Conclusion To design a differential encoder on Talrik I we first analysed physical constraints of the robot space around wheels positioning sensor then we compared various available coders and chose the encoder that fitted our requirements Then we determined how to interface the coders on
8. I to measure the direction of the wheels by analyzing the channels A and B There is no difference between the two solutions concerning the connections each of them uses two pins Direction Flip Flop Channel B ECE 8873 Georgia Tech Lorraine School of ECE IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot Between the two solutions we have chosen to use the hardware detection of the direction for the following reasons e The hardware solution spares computing time on the onboard computer e The Flip Flop prize is very low and it save software development costs So the price difference between the two solutions is small ECE 8873 Georgia Tech Lorraine School of ECE Q IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot II Choice of the encoder The constraints are the following e We need two encoders one per wheel e Each encoder must provide two channel quadrature outputs channels A and B e The precision on the position of the robot must be below two centimeters e The voltage supply of the encoder must be a single 5V supply since the voltage provided by the robot for the captor is a single 5V supply e The component must fit in the physical space that is available on the robot See III Physical description of the measure module e The price of the componen
9. Il Robot Here are the current descriptions and prices found on the website C2325a 6 Wire Serial Ribbon Cable 6 ft long with 1x6 female connectors on each end Price 9 95 C2325u 6 Wire Serial Ribbon Cable KIT 3 ft of ribbon wire connector s to make the C2325a Price 4 95 e Supply power to the MSCC11 board When reading MSCC11 s assembly manual we find out that MSCC11 is powered up using a 6 AA NiCd battery pack connected to the battery connections on board J52 and J53 J52 1 and J53 1 should receive plus terminal and J52 3 and J53 3 minus terminal using notations as in the manual page 9 The 6 AA NiCd battery pack can be the Talrik Junior s one purchasable at MEKATRONIX sellers 2 Connect encoders to MSCCI11 board On MSCC11 board plugs J44 to J51 can receive the 8 digital inputs A header is composed of a processor PortE input inner rail a Vec input middle rail and a ground input outer rail The connecting is done as follows J44 J45 J46 J47 A I B Grnd ENCODER 2 ECE 8873 Georgia Tech Lorraine School of ECE ENCODER 1 i932 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot V The algorithm A How to count the ticks The most difficult part is to detect when the value in the encoder changes and so we need to make the micro controller check very carefully what happens in the encoder Depending on the
10. aine School of ECE 19 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot Datasheet also provides the following encoder s electrical characteristics array Tammea o a oe T Velocity rpm x N 60 Shaft Perpendicularity 0 25 mm 6 9 mm 0 27 in from Plus Axial Play t in mounting surface Shaft Eccentricity Plus 0 04 mm in 6 9 mm 0 27 in from Radial Play 0 0015 TIR mounting surface Taken from HEDS 9040 datasheet Line 2 shows that each encoder requires a typical Vcc about 5V Here is a summary of electrical constraints brought by the encoders Type of outputs Channels A B and I are digital outputs Power requirements Vec 5V 32 7 KQ 10 pull up resistors to be mounted between I A and B outputs and N ie B Constraints of the robot The robot is composed of 2 main boards Processor board MRC11 Sensor expansion board MRSX0Ol1 As for the robot s internal communication system between components processor board comes with a 60 pin male header processor I O bus This bus communicates with MRSXO1 board through a ribbon MRSX0O1 board features 20 analog inputs and 2 digital inputs Talrik II communicates through logic signals 5V and ground coding the 2 logical states 1 and 0 ECE 8873 Georgia Tech Lorraine School of ECE _ 20 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of
11. annel quadrature outputs gt 128 counts per revolution gt single 5V supply The resolution of the encoder depends on the number of counts per revolution With this encoder we can see that the cheaper it is the lower the resolution 1s The datasheet of the component is available at http www farnell com datasheets 5064 pdf Conclusion The encoders of this category could be chosen Although they are not the cheapest ones they are not too expensive and their main advantage is to be already assembled which makes them easier and quicker to mount ECE 8873 Georgia Tech Lorraine School of ECE sio IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot C Category 3 encoders whose price is between 30 Euros and 100 Euros The different encoders grouped in this category are the cheapest encoders we could find These encoders are not assembled and this is the main reason why they are low cost components 1 Example 1 HEDS 9000 Figure HEDS 9000 Price 22 55 Euros Reference HEDS 9000 Features taken from the datasheet gt two channel quadrature outputs gt 2000 counts per revolution gt single 5V supply gt small size gt easy to mount gt no signal adjustment required ECE 8873 Georgia Tech Lorraine School of ECE Ce IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il R
12. assembly manual http www mekatronix com manuals PCB mscc 1 lam pdf MRC11 microcontroller assembly manual http www mekatronix com manuals PCB mrc 1 lam pdf MEKATRONIX s distributors www imrrobot com HEDS 9040 datasheet http www farnell com datasheets 6186 pdf Collins Dictionaries http wordreference com Image synthesis program http www newtek com Components http www farnell com http www radiospares com ECE 8873 Georgia Tech Lorraine School of ECE sIf
13. module the number of ticks it has received at a very precise frequency This time period should be much higher than the one on which the first module checks the signals of the encoders between 50 or 100 ns for example This module will ask how many ticks have been emitted will compute the distance covered by the robot and divide this value by the time period Example Given that the encoding wheel has 2 000 holes at a time period of 100 ns the module gets 6 000 ticks then 8 000 then 6 000 It means that the wheel of the robot has done 3 turns in 100 ns then 4 during the same amount of time then 3 again The instantaneous speed will be First 3 m 2 R 100 10 3 cm sec Then 4 m 2 R 100 10 3 cm sec And then 3 m 2 R 100 10 3 cm sec The hardest part is to choose an accurate frequency There is a trade off between a high frequency demanding much on the CPU and a low frequency that can result in a loss of information We have seen earlier that the maximum frequency accepted by the encoder is 100 kHz so we shouldn t choose a frequency higher than 200 kHz ECE 8873 Georgia Tech Lorraine School of ECE woe IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot D Program for the onboard computer The software is made of two functions that are triggered through timers Wait for x milliseconds Where x lt 2 Max frequency of Chan
14. nel A Measure the state of the two signals zo Signal A changed state Yes Test Way Signal Way Signal is high Way Signal is low Increment T register Decrement T register Wait for y x milliseconds Where x is the same x from the other function And y lt maximum value that T register can count Compute the distance in millimeters T Register contains 2 times the number of holes counted Zero T register and update position value IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 i Design of Differential Encoders for the Talrik II Robot VI Ordering Here is a summary sheet of all the parts that need to be ordered JRDER CONFIRMATION Recipient Material needed to mount a differential encoder on robot Talrik II Contact Dr HECK Company Deliverv address Georgia Tech Lorraine Account no Pat Georgia Tech Lorraine XXXX XXX 29 janvier 2003 2 avenue Marconi Address 57000 METZ 2 avenue Marconi FRANCE Post code Town 57000 METZ FRANCE Quantity Description Discount Total Where to buy Quantity 1 MSCC11E2U Unassembled 29 9558 0 29 95S www mrrobot com board amp components with MC68HC811E2 50 2 7 KQ 4 10 5 2 95 Ol 2 80S Farnell resistors euros 2o05 1 C2325u 6 Wire Serial A959 0 Ribbon Cable KIT 3 ft of ribbon wire connector s to make the CZ3258 1 AANCSB6 6 AA NiCd LL95 0O 11 95S www mrrobot com battery pack 1 HEDS 9040 Hewlett Packard 24 97 0 2
15. obot The datasheet of the component is available at http www farnell com datasheets 2616 pdf 2 Example 2 HEDS 9040 and HEDS 9140 The appearance of these encoders is exactly the same as the encoder HEDS 9000 The main differences are the following taken from the datasheet The HEDS 9040 and HEDS 9140 are three channel optical incremental encoder modules These modules provide the same performances found in the HEDS 9000 two channel encoder The HEDS 9040 and 9140 have two channel quadrature outputs plus a third channel index output The output of channel I index is an index impulse which is generated once for each full rotation of the code wheel Price 24 97 Euros Reference HEDS 9040 Features of the HEDS 9040 taken from the datasheet gt two channel quadrature outputs and index impulse gt 2000 counts per revolution So the precision constraint is repected gt single 5V supply gt small size gt easy to mount gt no signal adjustment required The datasheet of the component is available at http www farnell com datasheets 6186 pdf Conclusion We have decided to choose the component HEDS 9040 because it is one of the cheapest encoders that we found Moreover with this component we also have an index pulse that could be useful in the future ECE 8873 Georgia Tech Lorraine School of ECE 14 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Tal
16. of this category since their prices prevent us from choosing them for our design Conclusion the encoders of this category should not be chosen ECE 8873 Georgia Tech Lorraine School of ECE 10 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot B Category 2 encoders whose price is lower than 30 Euros This category of encoder is mainly composed of encoders whose prices are typically between 40 Euros and 50 Euros These encoders have the advantage of being already assembled Obviously their characteristics are not as good as those of the encoders of the category 1 but are still acceptable Let us consider some encoders of this category 1 Example 1 HEDS 5500 Figure HEDS 5500 Price 44 97 Euros Reference HEDS 5500 Features taken from the datasheet gt two channel quadrature outputs gt quick and easy assembly gt no signal adjustments required gt resolution up to 1024 counts per revolution gt single 5V supply The datasheet of the component is available at http www farnell com datasheets 7725 pdf ECE 8873 Georgia Tech Lorraine School of ECE 11 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot 2 Example 2 120EN 128 C24 Figure 12Q0EN 128 C24 Price 39 39 Euros Reference 120EN 128 C24 Features taken from the datasheet gt two ch
17. rik II Robot IHI Physical description of the measure module A Physical constraints The motorized wheels have an environment as described in the following picture Picture taken from under the robot ECE 8873 Georgia Tech Lorraine School of ECE 15 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot B Solution proposed We first looked for an incremental encoder tiny enough but with a reasonable prize The space between the motor and the wheel is very limited 5 mm The code wheel has a diameter of 25 4 mm and is hollowed for a 4 mm diameter axis The dimensions of the coder code wheel are shown on the following diagram WU p SC ECE 8873 Georgia Tech Lorraine School of ECE 7 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot To add the code wheel and the encoder we have to match two main constraints which are to fix the encoder and to prevent the wheel from moving out of its axis Any misalignment of the code wheel and the encoder would result in inaccurate measures To prevent any tilt from the wheel we will add a longer axis that will be fixed on a base fixed on the Talrik II through existing screws and bolts The base will also be used to fix the encoder The following picture shows the base It is made of pieces of wood 28 15 mm j 11 mm Note only
18. s 19 Bo Consan O A A a TODO ee A eee a eee cee eee anne ee 20 Ce POON rere ener ne teeter E Ste ety ere nen E etry eee a renee see 21 D Interfacing the encoders with the rob0t ccccccccccccccecceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 22 I Interface board MSCC11 with the robot eeeeeeenennnnnnnnsrrrrrrrrrrrrrrrrrrererrrrren pp 2 Connect encoders to MSCCUL board vssacisisscsvcachsosseshansiatsnecaeensbenssalasacaniaeneeriateteaeeias 23 V The algorithm 0 0 0 ccecccsesssccccccceeeeeeeeeeeeeesseseeeeesssnneeeeeeeeeeeeeeeeeeeeeseneeeeeessseaaaaeeeeeeeeeeeees 24 A TOV OCONEE eer E E E E A E AAE 24 B How lo measu he pos Onar E E st eauaand indentations 25 Ce MHowtomeasure thespian E 26 D Program ior ihe onboard COMPUTE Decca acereceesaanceeeuseceesmsateneuneceaeaaneneuseaeemeatensne 24 AA CST E E 28 CON O E E E E ne er eee ene ee 30 ECE 8873 Georgia Tech Lorraine School of ECE a Nia IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 i Design of Differential Encoders for the Talrik II Robot I Incremental encoder principle An incremental encoder system is a sensor that detects movements through optical detections of holes It is composed of two parts the code wheel and the encoder The code wheel is a piece of metal on which are regularly pierced holes on its outline Scheme Volts The code wheel goes inside the encoder in which the holes are tested To test if a hole is present or not
19. se aim should be to count the number of impulses received and to store them until another module asks for this number B How to measure the position We have seen that it should be very useful to use a first module to count the number of ticks emitted by the encoders The first operation to measure the position is to evaluate the distance and the way the robot moves Due to the flip flop device mounted between the encoder and the micro controller we can get the way of the motion very easily The distance is easy to get too Assuming that X ticks is the total number of ticks emitted by the encoder and received by the micro controller and n the number of holes in the encoder wheel is the number of rotations that the wheel has done So the distance D is given by the formula 2 ticksn R 25 n 74 where R is the radius of the wheel 3 7 This works quite very well if the robot goes straight If it turns we have to compute the angles between the straight position and the actual position for each wheel ECE 8873 Georgia Tech Lorraine School of ECE 25 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot C How to measure the speed The speed is equal to the distance divided by the time as this formula shows dx Ax V SS dt At We have already explained how to measure the distance We need to create a module which will ask the first
20. t should not be too high Based on their price we categorize three different types of optical encoders We will now underline the main characteristics of each category and the criteria of choice that will help us to select one of the available encoder The three categories are e the encoders whose price is higher than 100 Euros e the encoders whose price is between 30 Euros and 100 Euros e the encoders whose price is lower than 30 Euros A Category 1 encoders whose price ts higher than 100 Euros These optical encoders offer a very high precision They are easy to set up since they are already assembled However they are clearly unaffordable Moreover we must consider that we need one encoder per wheel so the price should be multiplied by two ECE 8873 Georgia Tech Lorraine School of ECE _9 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot Here is an example of an optical encoder of this category Figure RI58 S 0360AS 41K BPG Price 385 7 Euros Reference RI58 S 0360AS 41K BPG Features taken from the datasheet gt universal industrial encoder gt up to 40 000 step with 10 000 pulses gt high signal accuracy gt flexible due to many flange and connectors variants gt suitable for high shocks loads The datasheet of the component is available at www farnell com datasheets 27383 pdf It is needless to consider more precisely the encoders
21. the measures shown on the above picture are important for the measure precision ECE 8873 Georgia Tech Lorraine School of ECE aiT IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot Here is a diagram of the assembly of the axis in red the base in green the encoder in blue the code wheel in dark grey to the Talrik II The following picture shows the measure device once assembled on the Talrik II IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik Il Robot IV Interfacing encoder with the robot Electrical constraints Now that we have decided to use 2 encoders HEDS 9040 one for each motorized wheel we have to find out how to interface them with the robot A Electrical constraints of the encoders The HEDS 9040 datasheet provides the following electrical configuration TO OUTPUT LOGIC ONE TTL LOAD PER OUTPUT Taken from HEDS 9040 datasheet As shown above each encoder has 5 pins Pin 1 or ground pin Pins 2 3 and 5 or I A and B digital outputs Pin 4 or Vec pin It is also explained in the datasheet that the encoder requires 3 2 7 KQ 10 pull up resistors one for each digital output as shown above on the picture These pull up resistors should be placed as close as possible to the encoder itself within 4 feet ECE 8873 Georgia Tech Lorr
22. to retrieve the position and the speed of our robot analysing the signals emitted by them ECE 8873 Georgia Tech Lorraine School of ECE gt IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot 7241 6 10 62 6 nee ee ae eee ee eee ere eee eae 2 L Ineremental encoder Printiple rigcececsereceadewancacdersocacdemavsberentedecsemeaceeGien usd dertuseseeeenunssentucedoens 4 U Choice ofthe 2 MC OC 0 eenean e A ee EA EET EEEO ESET EEES 9 A Category encoders whose price is higher than 100 Euros cccccsseeeeeeeeeeeeeeees 9 B Category 2 encoders whose price is lower than 30 EUros cccccccccccceeeeeeeeeeeeeees 11 B Pape E EDS O a E EAA OEE 11 2 leap 2 POENT 23C 2A uea on EEE E E SN ET E RSi 12 C Category 3 encoders whose price is between 30 Euros and 100 Euros 008 13 be PET AE DS OUO ae EN 13 2 Example 2 HEDS 9040 and HEDS 9140 ooo cccccccccssssseeeeeeceeeessaaeeeeeeeeees 14 II Physical description of the measure module ce eeeeeesssseeeeeccceeeeeeeeeeeeaaaaeeeeeeseeeeees 15 Ae POY CIL CON A A a ce ee ee ere ee 15 B SONNO Proposed ERR eae te Rei er en i ei ERE ere een ee inaa RER 16 IV Interfacing encoder with the robot Electrical constraints ccccccccccecceeeeeeeeeeeeees 19 A Electrical constraints of the ENCOCETS vies cseccsescnsscepswerexasetonssennavecastenenecensaeecaaastoncnenseseers
23. wheel moves in the way of the arrow of the previous scheme time time The most common way to measure the difference of phase is to measure the logical state of one of the channels each time the other channel change its state An example is shown on the following diagrams where Trigger is written the measure of the logical state of the channel B is triggered by the rising front of the channel A To save this data a flip flop can be used to store the measured value Signal of channel B OUTPUT Signal of the Direction of the wheel Signal of channel A CLOCK a triggered on rising front Flip Flop Depending on the way the wheel is spinning the signal of the direction remains on low or high level between each time the flip flop is triggered If the wheel rotates in one constant way the direction signal will remain on the same logical level ECE 8873 Georgia Tech Lorraine School of ECE _6 IZAAC LEMARCHAND PERRIN PIEDNOIR January the 23 2003 Design of Differential Encoders for the Talrik II Robot Direct way the wheel moves in the way of the arrow Volts 4 N O O time Volts N A T f f time Volts o Direction i _ L a time a a Volts 4 N time Volts channel B time Volts o Direction pr aoe a B time C Trigger gt C Trigger However we could also use the micro controller of the Talrik I
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