root / branches / colonetmk2 / code / projects / libdragonfly / odometry.c @ 1456
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1 | 948 | justin | #include "odometry.h" |
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2 | 1456 | rcahoon | #include "encoders.h" |
3 | 948 | justin | #include <math.h> |
4 | #include <avr/interrupt.h> |
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5 | 1456 | rcahoon | #include "time.h" |
6 | #include "serial.h" |
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7 | 948 | justin | |
8 | long lround(double d); |
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9 | |||
10 | |||
11 | int encoder_ltm1, encoder_rtm1;
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12 | |||
13 | //Measure mm displacement in x and y from starting position. (+x:theta=0 +y:theta=M_PI/2)
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14 | 949 | justin | long diff_x,diff_y, velocity;
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15 | 948 | justin | |
16 | //Measures radian angle displacement from starting position. (initially 0)
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17 | double angle;
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18 | |||
19 | /**
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20 | * Retrieve the estimated x position. [millimeters]
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21 | */
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22 | long odometry_dx(void){ |
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23 | return diff_x;
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24 | } |
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25 | |||
26 | /**
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27 | * Retrieve the estimated y position. [millimeters]
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28 | */
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29 | long odometry_dy(void){ |
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30 | return diff_y;
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31 | } |
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32 | |||
33 | /**
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34 | * Retrieve the estimated angle [radians]
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35 | */
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36 | double odometry_angle(void){ |
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37 | return angle;
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38 | } |
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39 | |||
40 | 949 | justin | long odometry_velocity(void){ |
41 | return velocity;
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42 | } |
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43 | |||
44 | 948 | justin | /**
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45 | * Initializes odometry to run on timer 2.
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46 | * Also resets all values so that the center of the robot is
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47 | * considered to be at the origin facing the x direction.
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48 | */
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49 | void odometry_init(void){ |
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50 | |||
51 | encoders_init(); |
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52 | |||
53 | delay_ms(100);
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54 | |||
55 | odometry_reset(); |
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56 | |||
57 | |||
58 | //CTC Mode. CLK / 1024
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59 | TCCR2 = 0; // (Fully disconnected) |
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60 | TCCR2 = _BV(WGM21) | _BV(CS22) | _BV(CS20); //CLK/1024 , CTC Mode.
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61 | |||
62 | TIMSK |= _BV(OCIE2); |
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63 | |||
64 | OCR2 = ODOMETRY_CLK; |
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65 | } |
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66 | /**
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67 | * Resets all values so that the center of the robot is
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68 | * considered to be at the origin facing the x direction.
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69 | */
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70 | void odometry_reset(void){ |
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71 | diff_x = 0;
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72 | diff_y = 0;
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73 | encoder_ltm1 = encoder_read(LEFT); |
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74 | encoder_rtm1 = encoder_read(RIGHT); |
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75 | angle = 0.0; |
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76 | } |
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77 | |||
78 | |||
79 | void odometry_run(void){ |
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80 | //Angle swept through in a time step CCW-
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81 | double theta, rl, dc;
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82 | long dr,dl;
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83 | |||
84 | //Get the change in wheel positions
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85 | { |
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86 | int encoder_right = encoder_read(RIGHT);
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87 | int encoder_left = encoder_read(LEFT);
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88 | |||
89 | dl = encoder_left - encoder_ltm1; |
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90 | dr = encoder_right - encoder_rtm1; |
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91 | |||
92 | //No motion.
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93 | if(dl == 0 && dr == 0) return; |
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94 | |||
95 | encoder_ltm1 = encoder_left; |
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96 | encoder_rtm1 = encoder_right; |
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97 | |||
98 | // Try to avoid over/underflow.
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99 | dl = dl > 512 ? dl - 1024 :dl; |
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100 | dl = dl < -512 ? dl + 1024 :dl; |
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101 | dr = dr > 512 ? dr - 1024 :dr; |
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102 | dr = dr < -512 ? dr + 1024 :dr; |
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103 | |||
104 | //Convert "clicks" to um
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105 | dl *= CLICK_DISTANCE_UM; //um
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106 | dr *= CLICK_DISTANCE_UM; |
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107 | } |
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108 | |||
109 | |||
110 | if(dl == dr){
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111 | diff_x += lround(dl*cos(angle)/1000.0); //mm |
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112 | diff_y += lround(dl*sin(angle)/1000.0); //mm |
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113 | 949 | justin | velocity = lround((dl * 1000.0)/(ODOMETRY_CLK*TIME_SCALE)); //um / ms = mm/s |
114 | 1456 | rcahoon | usb_puts("dc: ");
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115 | usb_puti(dl); |
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116 | usb_puts("um, velocity: ");
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117 | usb_puti(velocity); |
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118 | usb_puts("\r\n mm/s");
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119 | 948 | justin | return;
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120 | } |
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121 | |||
122 | //Call the left wheel 0, clockwise positive.
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123 | rl = ((double)(ROBOT_WIDTH_UM*dl))/((double)(dl - dr)); //um |
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124 | theta = ((double)(dl - dr))/((double)ROBOT_WIDTH_UM); //rad |
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125 | |||
126 | //Distance the center has traveled.
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127 | 949 | justin | dc = (theta * (rl - ROBOT_WIDTH_UM)) / 2.0; //um |
128 | velocity = lround( dc * 1000 /(ODOMETRY_CLK*TIME_SCALE));
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129 | 1456 | rcahoon | usb_puts("dc: ");
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130 | usb_puti(dl); |
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131 | usb_puts("um, velocity: ");
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132 | usb_puti(velocity); |
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133 | usb_puts("\r\n mm/s");
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134 | 948 | justin | |
135 | //angle is necessarily CCW+, so subtract.
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136 | angle -= ANGLE_SCALE * theta; |
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137 | |||
138 | 949 | justin | //Change state variables. Probably lose all measurements less then a mm.
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139 | 948 | justin | diff_x += lround((DISTANCE_SCALE * dc * cos(angle))/1000.0); //mm |
140 | diff_y += lround((DISTANCE_SCALE * dc * sin(angle))/1000.0); //mm |
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141 | } |
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142 | |||
143 | ISR(TIMER2_COMP_vect){ |
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144 | odometry_run(); |
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145 | } |
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146 | |||
147 | long lround(double d){ |
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148 | double f = floor(d);
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149 | return (long)(d - f > 0.5 ? f + 1 : f); |
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150 | } |
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151 |