Parsian - Small Size Robot League
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1. 000 bps but it is said not to be used for frequencies less than 57600 when not applying any bit balancing algorithms to the data though the data must be byte balanced otherwise The XTR 434 transceiver can be set to transmitter receiver and power down modes When switching to transmitter or receiver the device needs 2ms to switch to the new mode And for Ims after it should not be used for data transmission but a rectangular pulse signal must be transmitted in the meantime As we did not use the available manufactured PCBs of the XTR 434 module we came across some problems using our self made circuit board The correct way of placing the module on a circuit board the antenna connection the ground circuits and the antenna which is used as said in the user s manual is noticeable for better performance 2 2 Data flow control Transmitter there is an AVR microcontroller in the transmitter circuit of the wireless communication board which is used to read the original data from the Control unit computer and to create a packet of processed data for the XTR 434 to transmit The serial Rx port of the AVR microcontroller has an interrupt subroutine which is called anytime it receives one byte of data When we receive 30 bytes of data 5 bytes for each robot we apply the bit balancing algorithm to the 30 original data bytes giving out 60 bytes of processed data with equal number of 1s and Os in each byte The rf_transmit function is then cal2. 8 is used to drive the wheels and spinner motors It has the capability of driving 2 motors simultaneously if biased correctly with diodes and right capacitors to avoid the unwanted feedback current and to control the maximum output voltage swing respectively Fig 2 Robot main electrical board 2 2 1 Quadrature encoder A feedback signal of the real output RPM of each motor is produced using a self made quadrature shaft encoder We have designed the shaft encoder manually There are two R receivers and one R transmitter used on the opposite sides of a latticed circular tape placed on the wheel s outside lap An 89C2051 microcontroller counts the number of pulses generated by the IR sensors circuit The motor s RPM and rotation direction is sent to the AVR controller 2 2 2 The PID system The PID system uses the encoder measured RPM of each wheel and sends back the appropriate feedback signal in case the measured RPM is different from what expected The PID system is used for each motor to keep the speed and acceleration of the robot as desired 2 Wireless Communication The wireless communication system consists of 3 main parts Fig 3 Transmitter board Designed based on AUREL XTR 434 2 1 Transceiver module We use an AUREL XTR 434 transceiver module for data transmission and reception The XTR 434 uses the carrier frequency of 433 92 MHz It s bandwidth is 150 KHz It can work in data frequencies between 9600 100
3. Parsian Amirkabir Univ of Technology Small Size Team Team Description Paper for Robocup 2006 Amir Amjad Amir Ghiasvand Mehdi Hooshyari Pour Mohammad Korjani Mohsen Roohani Shokoofeh Pourmehr Farzaneh Rastgari Vali Allah Monajjemi Moeen Nikzaad Larijani Sepehr Saadatmand Mani Milani Electrical Engineering Department Amirkabir University of Technology Tehran Polytechnic 424 Hafez Ave Postal Code 158754413 Tehran Iran webmaster parsianrobotic com Abstract This document Describes Parsian Robotic Small Size team activities for preparing for Robocup 2006 Small Size League It s an overview of all activities since November 2005 Parsian Robotic is a new comer to Small Size league and this document describes the major activities they made to start building Small Size Robots Our robots mechanical and electrical design wireless communication image processing and AI algorithms are described in this paper 1 Introduction Parsian Robotic is a robotic research group working in Electrical Engineering department of Amirkabir University of technology The team now consists of 10 active members Robocup 2006 is the opening tournament for this team to get participated in a Small Size League 2 Hardware Architecture 2 1 Mechanical Design The robot mechanical structure consists of motors wheels robot body and the gears Each robot has 3 wheels with relative polar angle of 120 degrees The motors power is transferred to the whe
4. basic RGB color such as blue is added to the gradient also When using this algorithm there is no need to seek for any other circles more than central team circles When a radial line of one color is found in the near vicinity of the central tam circles the identity and angle of the robot is found at the same time The gradient color tells the angle and the added color the ID 5 Artificial intelligence subsystem Artificial intelligence subsystem is divided into two parts In Beginner Layer AI each robot can do any activity such as going to new target kicking and passing It takes current game state and target game state robots and ball position velocities and robot orientation as input from expert_ layer AI and generate the tasks to switch current state to target state Expert Layer AI use reinforcement learning to select best activities It gets robots and ball position velocities and robot orientation as state current state and generates target state And submit the current and beginner state of robots to switch to target state with beginner _layer AI 5 1 Beginner Layer AI This layer takes current and target state of robots and reach the destination is it job The current state of a robot consists of the robot X and Y coordinates orientation and velocity A desired target state consists of the final X and Y coordinates final orientation final velocity or power of kicking In this section obstacle avoidance is
5. bbed frames sets a minimum limit to the capture device specifications which is discussed later The more the shutter speed of the camera is the more blur less will be the image that it provides This helps2 the noise reduction algorithm to give a more definite understanding of the playing field It was important to pay attention to the frame rate of the output video of the camera though most of the studied cameras would meet our need Due to the insufficient field of view of the original lens of the camera f 3 6 mm we decided to use an additional 0 42X wide lens The added Lens would provide even a wider view of field of play and so it would be easier to correct and repair the corner and border distortions of the captured image 4 2 Capturing video input At first we recorded some video streams and took some pictures of the playing field including the colored circles and other white boundary lines in order to start working on image processing algorithms It will be more talked about in the image processing section We started getting the camera output into the computer using the Firewire output of the camera and connecting it to a PCI IEEE 1394 port on the PC The Firewire connection to the computer would provides us with a noiseless input video and a picture resolution of even more than 640x480 pixels When we made sure about the camera and Firewire connection parameters we started challenging the VC libraries in order to get a real
6. els through the gears placed on the body of the robot while giving out 10 times more power The motors are Teac DC motors and the wheels are omni directional for the purpose of omni directional movement Fig 1 Mechanical Design 2 1 1 Shooting system The shooting operation is done by a solenoid with a metal core which is drawn to the front of the robot to hit the ball The solenoid moves the metal core radically when it is given a 100v input voltage 2 1 2 The spinner The spinner axis is parallel to the ground plain The roller is covered by rubber to catch and covers the ball fully when the ball hits it The spinner is placed at the height of 2 3cm the ball diameter at the front of the robot fixed by two holders The spinner motor rotates the roller through the related gears 2 2 Electrical Design We have followed 2 important goals in the design and production of the main Printed Circuit Board on each robot First the maximum task capabilities of the main board Second the least as possible the complexity of the board and its elements for easier debugging The main controlling job is carried out by an AVR ATmegal28 microcontroller The AVR microcontroller receives data from the wireless communication system using the serial Rx port Then the generated signal is sent to the motor drivers shooting system and the spinner The decided voltage for each motor is produced using Pulse Width Modulation A DC motor driver IC L 29
7. fferent alternatives we decided to use the same procedure as we did for the Firewire input Thus we are using the DirectX9 0 SDK directshow libraries to get the real time video into the VC project 4 3 Image processing strategies Fig 4 Camera Output Fig 5 Rendered Image After studying the other and previous teams documents and some other references about the image processing procedures we decided to use the color threshold algorithms in the RGB color applet As the first attempt we tested the tow state thresholds for RGB colors and so we reduced the total colors to only 8 out of 24bits We did this using the recorded video streams and captured pictures in the MATLAB 6 5 environment Afterwards we examined and tested some different colors and environmental parameters affecting the delicacy of the algorithm We found out that the tow state thresholds for all basic RGB colors would not produce as many colors as we would need So we decided to use three state color thresholds for at least one of the basic RGB colors Using this we are able to produce at least 12 easily distinguishable colors In order to identify each robot distinctively we used some different patterns of circles that we painted in one of those 12 colors Each robot is distinctively identified by these colored circles that are placed on top of each robot considering the arrangement of the circles In order to locate the circles of each color we thought of
8. led to create a packet containing lms of rectangular pulse signal plus one start byte plus two bytes containing the number of the bytes to be transmitted Then the bit balanced data followed by two ending bytes are added to the created packet The whole packet is sent to the XTR 434 Tx port using the serial Tx port of the AVR microcontroller for transmission Receiver there is an AVR microcontroller on the receiver circuit board of the wireless communication system on each robot which gets the received packet from the XTR 434 Rx port It then decodes the received packet in order to reconstruct the original data The data is checked for any errors using 3 different procedures before being passed to the next unit 3 3 Serial connection to the computer The serial RS232 COM port of the Control unit computer is used to send data to and receive any needed data from the AVR microcontroller A MAX 232 IC is used to convert the 12 and 12 volts of the COM port to the operating logic voltages of the circuit elements that is 0 and 5 4 Vision System 4 1 Global vision system Studying some different documents and data sheets and parameters of different cameras we decided to use a CCD Analogue camera Some important parameters of the camera to use are discussed below The resolution of the camera output video must be at least 640x480 pixels so that the image processing algorithm can give a better and more delicate output The resolution of the gra
9. solved by minimizing the energy using Hopfield neural networks 5 2 Expert Layer AI Expert Layer AI takes robot coordinates orientation and velocities as input from vision system Expert _layer AI divided the field of play into squares and initialized a list of activities by position of it to each square In this section game divided to three states defensive offensive and general And arrange the activities by priority of each activity Then deleted each of them that completely infeasible Finally expert layer AI choose the most suitable activity from top of the list For example in 1 3 defensive area of play kicking has best priority and dripping has lowest priority References 1 Siegwart Roland Introduction to Autonomous Mobile Robots 2004 MIT Press 2 Nils J Nilsson Introduction to Machine Learning Department of Computer Science Stanford University
10. some different ways of processing the matrix of the image among which I will briefly explain two most inspiring ones e One way of locating the circles is to read all the pixels of the grabbed frame without bypassing any important or redundant pixels In this case a chosen pattern that best represents a circle will scan the whole image and find all the circles and finally drop the invalid circles found Note that in this procedure quite a lot of CPU usage and memory space will be used This will cause the program not to be able to produce as many new frame data as we need e Another way of locating the circles is to read not ALL the pixels of the image matrix In this case a different pattern will sweep the whole picture but dropping about 95 of the pixels if they don t contain important material This is the procedure we are using now To identify each robot and find the angles needed the algorithm goes through some routine mathematical calculations then As the last job of the image processing unit all the needed locations and angles and traces are passed to the control unit which will control the robot movements NOTE As an image processing algorithm proposal I would like to explain another way to identify and locate the robots In this procedure a complete gradient of the most distinguishable RGB basic color such as green is printed on a ring paper and placed on top of the robot To identify each robot a threshold color of another
11. time video from the connected camera and with the least possible delay In that case we decided to use the DirectX9 0 SDK libraries and drivers in order to get the grabbed frames directly into the VC project While doing so to grab the video input we came across two main problems First we noticed a significant delay between the real time video and the input video Studying the DirectX SDK libraries we found that a software based decoder is used after the frame is grabbed from the DV input This would produce the delay Second we couldn t find the needed extension repeaters for the Firewire cable so that we could connect a 4meters high camera to the PC As we didn t have the very time to spend on solving these problems we decided to use a capture card with the analogue output of the camera We use a coaxial shielded cable to transfer data from the analogue output of the camera to the PC When using a capture card we would have to pay attention to the output frame rate and resolution capabilities of the capture card The maximum resolution of 640x480px of the capture card would limit the video input maximum frame rate to 30 fps When using a capture card another way to get the grabbed frame into the VC codes is to read the capture card s memory This can be done by directly reading the memory without using the computer CPU in the overlay mode of the capture card or using the computer CPU to read data in the preview mode Considering the di
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