root / trunk / code / projects / mapping / odometry / odometry.c @ 948
History | View | Annotate | Download (2.77 KB)
1 |
#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 |
long diff_x,diff_y;
|
14 |
|
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 |
/**
|
40 |
* Initializes odometry to run on timer 2.
|
41 |
* Also resets all values so that the center of the robot is
|
42 |
* considered to be at the origin facing the x direction.
|
43 |
*/
|
44 |
void odometry_init(void){ |
45 |
|
46 |
encoders_init(); |
47 |
|
48 |
delay_ms(100);
|
49 |
|
50 |
odometry_reset(); |
51 |
|
52 |
|
53 |
//CTC Mode. CLK / 1024
|
54 |
TCCR2 = 0; // (Fully disconnected) |
55 |
TCCR2 = _BV(WGM21) | _BV(CS22) | _BV(CS20); //CLK/1024 , CTC Mode.
|
56 |
|
57 |
TIMSK |= _BV(OCIE2); |
58 |
|
59 |
OCR2 = ODOMETRY_CLK; |
60 |
} |
61 |
/**
|
62 |
* Resets all values so that the center of the robot is
|
63 |
* considered to be at the origin facing the x direction.
|
64 |
*/
|
65 |
void odometry_reset(void){ |
66 |
diff_x = 0;
|
67 |
diff_y = 0;
|
68 |
encoder_ltm1 = encoder_read(LEFT); |
69 |
encoder_rtm1 = encoder_read(RIGHT); |
70 |
angle = 0.0; |
71 |
} |
72 |
|
73 |
|
74 |
void odometry_run(void){ |
75 |
//Angle swept through in a time step CCW-
|
76 |
double theta, rl, dc;
|
77 |
long dr,dl;
|
78 |
|
79 |
//Get the change in wheel positions
|
80 |
{ |
81 |
int encoder_right = encoder_read(RIGHT);
|
82 |
int encoder_left = encoder_read(LEFT);
|
83 |
|
84 |
dl = encoder_left - encoder_ltm1; |
85 |
dr = encoder_right - encoder_rtm1; |
86 |
|
87 |
//No motion.
|
88 |
if(dl == 0 && dr == 0) return; |
89 |
|
90 |
encoder_ltm1 = encoder_left; |
91 |
encoder_rtm1 = encoder_right; |
92 |
|
93 |
// Try to avoid over/underflow.
|
94 |
dl = dl > 512 ? dl - 1024 :dl; |
95 |
dl = dl < -512 ? dl + 1024 :dl; |
96 |
dr = dr > 512 ? dr - 1024 :dr; |
97 |
dr = dr < -512 ? dr + 1024 :dr; |
98 |
|
99 |
//Convert "clicks" to um
|
100 |
dl *= CLICK_DISTANCE_UM; //um
|
101 |
dr *= CLICK_DISTANCE_UM; |
102 |
} |
103 |
|
104 |
|
105 |
if(dl == dr){
|
106 |
diff_x += lround(dl*cos(angle)/1000.0); //mm |
107 |
diff_y += lround(dl*sin(angle)/1000.0); //mm |
108 |
return;
|
109 |
} |
110 |
|
111 |
//Call the left wheel 0, clockwise positive.
|
112 |
rl = ((double)(ROBOT_WIDTH_UM*dl))/((double)(dl - dr)); //um |
113 |
theta = ((double)(dl - dr))/((double)ROBOT_WIDTH_UM); //rad |
114 |
|
115 |
//Distance the center has traveled.
|
116 |
dc = lround( (theta * (rl - ROBOT_WIDTH_UM)) / 2.0 ); //um |
117 |
|
118 |
//angle is necessarily CCW+, so subtract.
|
119 |
angle -= ANGLE_SCALE * theta; |
120 |
|
121 |
//Change state variables.
|
122 |
diff_x += lround((DISTANCE_SCALE * dc * cos(angle))/1000.0); //mm |
123 |
diff_y += lround((DISTANCE_SCALE * dc * sin(angle))/1000.0); //mm |
124 |
} |
125 |
|
126 |
ISR(TIMER2_COMP_vect){ |
127 |
odometry_run(); |
128 |
} |
129 |
|
130 |
long lround(double d){ |
131 |
double f = floor(d);
|
132 |
return (long)(d - f > 0.5 ? f + 1 : f); |
133 |
} |
134 |
|
135 |
|