root / branches / library_refactor / projects / libdragonfly / odometry.c @ 1624
History | View | Annotate | Download (3.17 KB)
1 | 948 | justin | #include "odometry.h" |
---|---|---|---|
2 | #include <encoders.h> |
||
3 | #include <math.h> |
||
4 | #include <avr/interrupt.h> |
||
5 | #include <dragonfly_lib.h> |
||
6 | |||
7 | long lround(double d); |
||
8 | |||
9 | |||
10 | int encoder_ltm1, encoder_rtm1;
|
||
11 | |||
12 | //Measure mm displacement in x and y from starting position. (+x:theta=0 +y:theta=M_PI/2)
|
||
13 | 949 | justin | long diff_x,diff_y, velocity;
|
14 | 948 | justin | |
15 | //Measures radian angle displacement from starting position. (initially 0)
|
||
16 | double angle;
|
||
17 | |||
18 | /**
|
||
19 | * Retrieve the estimated x position. [millimeters]
|
||
20 | */
|
||
21 | long odometry_dx(void){ |
||
22 | return diff_x;
|
||
23 | } |
||
24 | |||
25 | /**
|
||
26 | * Retrieve the estimated y position. [millimeters]
|
||
27 | */
|
||
28 | long odometry_dy(void){ |
||
29 | return diff_y;
|
||
30 | } |
||
31 | |||
32 | /**
|
||
33 | * Retrieve the estimated angle [radians]
|
||
34 | */
|
||
35 | double odometry_angle(void){ |
||
36 | return angle;
|
||
37 | } |
||
38 | |||
39 | 949 | justin | long odometry_velocity(void){ |
40 | return velocity;
|
||
41 | } |
||
42 | |||
43 | 948 | justin | /**
|
44 | * Initializes odometry to run on timer 2.
|
||
45 | * Also resets all values so that the center of the robot is
|
||
46 | * considered to be at the origin facing the x direction.
|
||
47 | */
|
||
48 | void odometry_init(void){ |
||
49 | |||
50 | encoders_init(); |
||
51 | |||
52 | delay_ms(100);
|
||
53 | |||
54 | odometry_reset(); |
||
55 | |||
56 | |||
57 | //CTC Mode. CLK / 1024
|
||
58 | TCCR2 = 0; // (Fully disconnected) |
||
59 | TCCR2 = _BV(WGM21) | _BV(CS22) | _BV(CS20); //CLK/1024 , CTC Mode.
|
||
60 | |||
61 | TIMSK |= _BV(OCIE2); |
||
62 | |||
63 | OCR2 = ODOMETRY_CLK; |
||
64 | } |
||
65 | /**
|
||
66 | * Resets all values so that the center of the robot is
|
||
67 | * considered to be at the origin facing the x direction.
|
||
68 | */
|
||
69 | void odometry_reset(void){ |
||
70 | diff_x = 0;
|
||
71 | diff_y = 0;
|
||
72 | encoder_ltm1 = encoder_read(LEFT); |
||
73 | encoder_rtm1 = encoder_read(RIGHT); |
||
74 | angle = 0.0; |
||
75 | } |
||
76 | |||
77 | |||
78 | void odometry_run(void){ |
||
79 | //Angle swept through in a time step CCW-
|
||
80 | double theta, rl, dc;
|
||
81 | long dr,dl;
|
||
82 | 949 | justin | char buf[100]; |
83 | 948 | justin | |
84 | //Get the change in wheel positions
|
||
85 | { |
||
86 | int encoder_right = encoder_read(RIGHT);
|
||
87 | int encoder_left = encoder_read(LEFT);
|
||
88 | |||
89 | dl = encoder_left - encoder_ltm1; |
||
90 | dr = encoder_right - encoder_rtm1; |
||
91 | |||
92 | //No motion.
|
||
93 | if(dl == 0 && dr == 0) return; |
||
94 | |||
95 | encoder_ltm1 = encoder_left; |
||
96 | encoder_rtm1 = encoder_right; |
||
97 | |||
98 | // Try to avoid over/underflow.
|
||
99 | dl = dl > 512 ? dl - 1024 :dl; |
||
100 | dl = dl < -512 ? dl + 1024 :dl; |
||
101 | dr = dr > 512 ? dr - 1024 :dr; |
||
102 | dr = dr < -512 ? dr + 1024 :dr; |
||
103 | |||
104 | //Convert "clicks" to um
|
||
105 | dl *= CLICK_DISTANCE_UM; //um
|
||
106 | dr *= CLICK_DISTANCE_UM; |
||
107 | } |
||
108 | |||
109 | |||
110 | if(dl == dr){
|
||
111 | diff_x += lround(dl*cos(angle)/1000.0); //mm |
||
112 | diff_y += lround(dl*sin(angle)/1000.0); //mm |
||
113 | 949 | justin | velocity = lround((dl * 1000.0)/(ODOMETRY_CLK*TIME_SCALE)); //um / ms = mm/s |
114 | sprintf(buf,"dc: %ld, velocity: %ld\r\n mm/s",dl,velocity);
|
||
115 | usb_puts(buf); |
||
116 | 948 | justin | return;
|
117 | } |
||
118 | |||
119 | //Call the left wheel 0, clockwise positive.
|
||
120 | rl = ((double)(ROBOT_WIDTH_UM*dl))/((double)(dl - dr)); //um |
||
121 | theta = ((double)(dl - dr))/((double)ROBOT_WIDTH_UM); //rad |
||
122 | |||
123 | //Distance the center has traveled.
|
||
124 | 949 | justin | dc = (theta * (rl - ROBOT_WIDTH_UM)) / 2.0; //um |
125 | velocity = lround( dc * 1000 /(ODOMETRY_CLK*TIME_SCALE));
|
||
126 | sprintf(buf,"dc: %lfum, velocity: %ld\r\n mm/s",dc,velocity);
|
||
127 | usb_puts(buf); |
||
128 | 948 | justin | |
129 | //angle is necessarily CCW+, so subtract.
|
||
130 | angle -= ANGLE_SCALE * theta; |
||
131 | |||
132 | 949 | justin | //Change state variables. Probably lose all measurements less then a mm.
|
133 | 948 | justin | diff_x += lround((DISTANCE_SCALE * dc * cos(angle))/1000.0); //mm |
134 | diff_y += lround((DISTANCE_SCALE * dc * sin(angle))/1000.0); //mm |
||
135 | } |
||
136 | |||
137 | ISR(TIMER2_COMP_vect){ |
||
138 | odometry_run(); |
||
139 | } |
||
140 | |||
141 | long lround(double d){ |
||
142 | double f = floor(d);
|
||
143 | return (long)(d - f > 0.5 ? f + 1 : f); |
||
144 | } |
||
145 |