Submitted version of the thesis - Airlab, the Artificial Intelligence ...

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48 Chapter 4. Control distance to the target position. Each distance is divided by a constant, then multiplied with the multiplier defined as FAST, NORMAL and CLOSE. Then another constant which is the minimum value that can initiate the motors movement is added. Hence, the mapping that each value set by the PWM signal generates a motion, is achieved. The multipliers are defined according to the distance of the robot to the target object. For the distances between 1200 mm and greater, the corresponding multiplier is classified as FAST, between 1200 mm and 750 mm the multiplier is NORMAL, and for the distances between 750 mm and 300 mm it is CLOSE. By defining such control mechanism as FAST, NORMAL, CLOSE we are able to create three different speed limits for the motors, which are all mapped from 60% to 85% of the duty cycle where the motion is visible. As an example case, when the robot detects a target at 3 meters, the motor speeds will be set with multiplier FAST until the distance to the target reaches 1.2 meters. When reached to 1.2 meters, the motor speed will be set with multiplier NORMAL until the detected target distance is less than 700 millimeters. And finally, the motors speeds will be set with multiplier CLOSE from 700 mm until the target is reached. This mechanism allows to achieve more precision in the motion, since the mapping guarantees that each motor speed set by PWM will generate areasonablemotion. Moreover, insteadof tryingtomapall the speeds uniquely, indeed we are trying to map only one third of the speeds, from the predefined speed ranges to 60%-85% of the PWM value in the duty cycle. Even though the robot goes to target with an unexpected path, the path is corrected as the robot comes closer since the slow motor speeds are more precise and easy to achieve. Even though the solution is not working perfectly, the robot is able to go to the target successfully almost every time. The travel time and number of movements in order to reach the target are not optimal, but this result should be regarded as normal since we are not using any encoder to detect the movement in the motors. The need for an optimization of the PWM signal is also related to the result of the miscalculation of the required torque. We selected motors that do not have enough torque power for our robot. This brought the problem of the arrangement of the PWM signal in order to run the motors. Since the motors have less torque than we expected, almost 50% of the PWM is wasted. First trials to optimize this inefficiency have been made by changing the frequency of the PWM to a higher or a lower frequency, but these trials did not give good results. Later, we found the proper configuration,
4.3. PWM Control 49 mentioned previously, by limiting the minimum and maximum PWM values of the motors and by introducing the fuzzy-like control to introduce different limits for the different distances to target. Even though the lack of the encoders reduced the performance, we were able to produce an acceptable configuration. Another step is initialization of the motors. The corresponding pins in the microcontroller for the motors are set to control the direction of motors and PWM generation. The PWM generation is made by using the timers available in the microcontroller. Output compare mode of the timers is usedinordertocreate thePWMneededtorunthemotors. Outputcompare function is used to control the output waveform and indicates when a period of time has elapsed. When a match is found between the output compare register and the counter, the output compare function: • Assigns a value to pins • Sets a flag in the status register • Generates an interrupt Using the described output comparison, we created the desired PWM wave to run the motors. At, first the timer clock is set to 8 mHZ. Then output compare register 1 is set for the desired motor speed as some percentage of the full period of the cycle. Output compare register 2 is set to full cycle that will set the pin to HIGH, and update the desired motor speed of the output compare register 1. When counter reaches the defined value, the motor speeds will be updated and the pins will be reset. It will remain LOW until output compare register 2 value (which is the full period) is reached. Using that algorithm we generate the PWM signal to run the motor. For each motor, we decided to use a separate timer, since the timers are available to use and not needed by other applications. It is also possible to use only one timer to generate the PWM’s for all the motors using the interrupts and output compare registers, but we decided not to use like this for the simplicity of the algorithm, since this will need a better synchronization, and optimization to run efficiently. The control of the servo that is changing the camera head pointing direction is also implemented using PWM signals. For the servo PWM, we don’t have the problem of control that we faced with the motors. So, no tunings
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POLITECNICO DI MILANO Corso di Laur
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To my family...
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Summary Aim of this project is the
Page 13 and 14: Contents Sommario I Summary III Tha
Page 15 and 16: List of Figures 2.1 The standard wh
Page 17 and 18: Chapter 1 Introduction 1.1 Goals Th
Page 19 and 20: 1.4. Thesis Structure 3 tailed desc
Page 21 and 22: Chapter 2 State of the Art Advances
Page 23 and 24: 2.1. Locomotion 7 provides low resi
Page 25 and 26: 2.1. Locomotion 9 Figure 2.4: Diffe
Page 27 and 28: 2.1. Locomotion 11 Omnidirectional
Page 29 and 30: 2.2. Motion Models 13 2.2 Motion Mo
Page 31 and 32: 2.4. Games and Interaction 15 a 2.5
Page 33 and 34: 2.4. Games and Interaction 17 We in
Page 35 and 36: 2.4. Games and Interaction 19 lot o
Page 37 and 38: Chapter 3 Mechanical Construction W
Page 39 and 40: 3.2. Motors 23 The initial design o
Page 41 and 42: 3.2. Motors 25 Figure 3.3: The calc
Page 43 and 44: 3.3. Wheels 27 target surface, maxi
Page 45 and 46: 3.5. Bumpers 29 Figure 3.8: Three w
Page 47 and 48: 3.6. Batteries 31 itself also works
Page 49 and 50: 3.7. Hardware Architecture 33 In sh
Page 51 and 52: 3.7. Hardware Architecture 35 The s
Page 53 and 54: 3.7. Hardware Architecture 37 With
Page 55 and 56: Chapter 4 Control The motion mechan
Page 57 and 58: 4.1. Wheel configuration 41 Figure
Page 59 and 60: 4.2. Matlab Script 43 This is case
Page 61 and 62: 4.2. Matlab Script 45 Mixed Angular
Page 63: 4.3. PWM Control 47 acollision, suc
Page 67 and 68: Chapter 5 Vision The vision system
Page 69 and 70: 5.1. Camera Calibration 53 the prin
Page 71 and 72: 5.1. Camera Calibration 55 Figure 5
Page 73 and 74: 5.1. Camera Calibration 57 Later, i
Page 75 and 76: 5.2. Color Definition 59 warmer (ye
Page 77 and 78: 5.2. Color Definition 61 Anotheraut
Page 79 and 80: 5.2. Color Definition 63 9000 8000
Page 81 and 82: 5.3. Tracking 65 any color values.
Page 83 and 84: Chapter 6 Game The robot will be us
Page 85 and 86: • Initialize sensors • Initiali
Page 87 and 88: If the camera is set to SERVO MID,
Page 89 and 90: Chapter 7 Conclusions and Future Wo
Page 91 and 92: ior, which will be useful in the re
Page 93 and 94: Bibliography [1] Battle bots-http:/
Page 95 and 96: BIBLIOGRAPHY 79 [25] Han et al. A n
Page 97 and 98: Appendix A Documentation of the pro
Page 99 and 100: Figure A.2: The flow diagram of the
Page 101 and 102: Appendix B Documentation of the pro
Page 103 and 104: B.1. Microprocessor Code 87 /* Conf
Page 105 and 106: B.1. Microprocessor Code 89 #ifdef
Page 107 and 108: B.1. Microprocessor Code 91 Set_Spe
Page 109 and 110: B.1. Microprocessor Code 93 TIM_DeI
Page 111 and 112: B.1. Microprocessor Code 95 /* Expo
Page 113 and 114: B.1. Microprocessor Code 97 RGBCube
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B.1. Microprocessor Code 99 /* Incl
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B.1. Microprocessor Code 101 #endif
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B.1. Microprocessor Code 103 } void
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B.1. Microprocessor Code 105 GPIO_I
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B.1. Microprocessor Code 107 /* Sta
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B.1. Microprocessor Code 109 } Inve
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B.1. Microprocessor Code 111 #inclu
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B.1. Microprocessor Code 113 /* * M
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B.1. Microprocessor Code 115 b[1] =
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B.1. Microprocessor Code 117 } * (B
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B.1. Microprocessor Code 119 #defin
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B.2. Color Histogram Calculator 121
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B.3. Object’s Position Calculator
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B.3. Object’s Position Calculator
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B.4. Motion Simulator 127 0 0 0 0 0
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B.4. Motion Simulator 129 if (plot
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B.4. Motion Simulator 131 fill (m a
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B.4. Motion Simulator 133 end text(
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Appendix C User Manual This documen
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C.1. Tool-chain Software 137 Figure
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C.2. Setting up the environment (Qt
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C.3. Main Software - Game software
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Appendix D Datasheet The pin mappin
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Figure D.2: The schematics for the
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