summaryrefslogtreecommitdiff
path: root/n/asserv/src/asserv/pos.c
blob: eecd71f3c07f6488f425d7d6a37242fd8fa1e45a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
/* pos.c - Position motor control. */
/* asserv - Position & speed motor control on AVR. {{{
 *
 * Copyright (C) 2005 Nicolas Schodet
 *
 * Robot APB Team/Efrei 2006.
 *        Web: http://assos.efrei.fr/robot/
 *      Email: robot AT efrei DOT fr
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * }}} */

/**
 * This file is responsible for position motor control.  The consign is a
 * position of the motor shafts, as theta/alpha.  Theta is the sum of right
 * and left position, alpha is the difference between the right and the left
 * position.
 * 16 bits are enough as long as there is no long blocking (see 2005 cup!).
 */

/** Current theta/alpha. */
uint32_t pos_theta_cur, pos_alpha_cur;
/** Consign theta/alpha. */
uint32_t pos_theta_cons, pos_alpha_cons;

/** Error saturation. */
int32_t pos_e_sat = 1023;
/** Integral saturation. */
int32_t pos_int_sat = 1023;
/** P coefficients. */
uint16_t pos_theta_kp, pos_alpha_kp;
/** I coefficients. */
uint16_t pos_theta_ki, pos_alpha_ki;
/** D coefficients. */
uint16_t pos_theta_kd, pos_alpha_kd;
/** Blocked value.  If error is greater than this value, stop the robot and
 * report blocked state. */
int32_t pos_blocked = 15000L;

/** Current integral values. */
int32_t pos_theta_int, pos_alpha_int;
/** Last error values. */
int32_t pos_theta_e_old, pos_alpha_e_old;
/** One if blocked. */
uint8_t pos_blocked_state;

/* +AutoDec */
/* -AutoDec */

/** Compute a PID.
 * How to compute maximum numbers size:
 * Result is 24 bits (16 bits kept after shift).
 * If e_sat == 1023, e max is 11 bits (do not forget the sign bit), and diff
 * max is 12 bits.
 * If int_sat == 1023, i max is 11 bits.
 * In the final addition, let's give 23 bits to the p part, and 22 bits to the
 * i and d part (23b + 22b + 22b => 23b + 23b => 24b). 
 * Therefore, kp can be 23 - 11 = 12 bits (f4.8).
 *            ki can be 22 - 11 = 11 bits (f3.8).
 *            kd can be 22 - 12 = 10 bits (f2.8).
 * How to increase this number:
 *  - lower the shift.
 *  - bound the value returned.
 *  - lower e & int saturation. */
static inline int16_t
pos_compute_pid (int32_t e, int32_t *i, int32_t *e_old,
		 uint16_t kp, uint16_t ki, uint16_t kd)
{
    int32_t diff, pid;
    /* Saturate error. */
    UTILS_BOUND (e, -pos_e_sat, pos_e_sat);
    /* Integral update. */
    *i += e;
    UTILS_BOUND (*i, -pos_int_sat, pos_int_sat);
    /* Differential value. */
    diff = e - *e_old;
    /* Compute PID. */
    pid = e * kp + *i * ki + diff * kd;
    /* Save result. */
    *e_old = e;
    return pid >> 8;
}

/** Update PWM according to consign. */
static void
pos_update (void)
{
    int16_t pid_theta, pid_alpha;
    int32_t diff_theta, diff_alpha;
    /* Update current shaft positions. */
    pos_theta_cur += counter_left_diff + counter_right_diff;
    pos_alpha_cur += counter_right_diff - counter_left_diff;
    /* Compute PID. */
    diff_theta = pos_theta_cons - pos_theta_cur;
    diff_alpha = pos_alpha_cons - pos_alpha_cur;
    if (pos_blocked_state
	|| diff_theta < -pos_blocked || pos_blocked < diff_theta
	|| diff_alpha < -pos_blocked || pos_blocked < diff_alpha)
      {
	/* Blocked. */
	pwm_left = 0;
	pwm_right = 0;
	pos_blocked_state = 1;
	main_sequence_finish = main_sequence | 0x80;
      }
    else
      {
	pid_theta = pos_compute_pid (diff_theta, &pos_theta_int,
				     &pos_theta_e_old, pos_theta_kp,
				     pos_theta_ki, pos_theta_kd);
	pid_alpha = pos_compute_pid (diff_alpha, &pos_alpha_int,
				     &pos_alpha_e_old, pos_alpha_kp,
				     pos_alpha_ki, pos_alpha_kd);
	/* Update PWM. */
	pwm_left = pid_theta - pid_alpha;
	UTILS_BOUND (pwm_left, -PWM_MAX, PWM_MAX);
	pwm_right = pid_theta + pid_alpha;
	UTILS_BOUND (pwm_right, -PWM_MAX, PWM_MAX);
      }
}

/** Reset position control internal state. */
static void
pos_reset (void)
{
    pos_theta_int = pos_alpha_int = 0;
    pos_theta_cur = pos_alpha_cur = 0;
    pos_theta_cons = pos_alpha_cons = 0;
    pos_theta_e_old = pos_alpha_e_old = 0;
    pos_blocked_state = 0;
}