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+/* pos.c - Position motor control. */
+/* asserv - Position & speed motor control on AVR. {{{
+ *
+ * Copyright (C) 2005 Nicolas Schodet
+ *
+ * APBTeam:
+ * Web: http://apbteam.org/
+ * Email: team AT apbteam DOT org
+ *
+ * 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.
+ *
+ * }}} */
+#include "common.h"
+#include "pos.h"
+
+#include "modules/utils/utils.h"
+#include "modules/math/fixed/fixed.h"
+
+#include "counter.h"
+#include "pwm.h"
+#include "state.h"
+
+/**
+ * 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!).
+ */
+
+/** Auxiliaries control states. */
+struct pos_t pos_aux[AC_ASSERV_AUX_NB];
+
+/** Error saturation. */
+int32_t pos_e_sat = 1023;
+/** Integral saturation. */
+int32_t pos_i_sat = 1023;
+/** Differential saturation. */
+int32_t pos_d_sat = 1023;
+
+/** 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 (can be saturated with d_sat).
+ * If i_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, i & d saturation. */
+static inline int16_t
+pos_compute_pid (int32_t e, struct pos_t *pos)
+{
+ int32_t diff, pid;
+ /* Saturate error. */
+ UTILS_BOUND (e, -pos_e_sat, pos_e_sat);
+ /* Integral update. */
+ pos->i += e;
+ UTILS_BOUND (pos->i, -pos_i_sat, pos_i_sat);
+ /* Differential value. */
+ diff = e - pos->e_old;
+ UTILS_BOUND (diff, -pos_d_sat, pos_d_sat);
+ /* Compute PID. */
+ pid = e * pos->kp + pos->i * pos->ki + diff * pos->kd;
+ /* Save result. */
+ pos->e_old = e;
+ return pid >> 8;
+}
+
+/** Update PWM for a single motor system. */
+static void
+pos_update_single (struct state_t *state, struct pos_t *pos,
+ int16_t counter_diff, struct pwm_t *pwm)
+{
+ if (state->mode >= MODE_POS)
+ {
+ int16_t pid;
+ int32_t error;
+ /* Update current shaft position. */
+ pos->cur += counter_diff;
+ /* Compute error. */
+ error = pos->cons - pos->cur;
+ /* Test or blocking. */
+ if (UTILS_ABS (error) > pos->blocked_error_limit
+ && UTILS_ABS (counter_diff) < pos->blocked_speed_limit)
+ pos->blocked_counter++;
+ else
+ pos->blocked_counter = 0;
+ if (!(state->variant & 4)
+ && pos->blocked_counter > pos->blocked_counter_limit)
+ {
+ /* Blocked. */
+ pos_reset (pos);
+ state_blocked (state);
+ pwm_set (pwm, 0);
+ }
+ else
+ {
+ /* Compute PID. */
+ pid = pos_compute_pid (error, pos);
+ /* Update PWM. */
+ pwm_set (pwm, pid);
+ }
+ }
+}
+
+/** Update PWM according to consign. */
+void
+pos_update (void)
+{
+ uint8_t i;
+ for (i = 0; i < AC_ASSERV_AUX_NB; i++)
+ pos_update_single (&state_aux[i], &pos_aux[i], counter_aux_diff[i],
+ &pwm_aux[i]);
+}
+
+/** Reset position control state. To be called when the position control is
+ * deactivated. */
+void
+pos_reset (struct pos_t *pos)
+{
+ pos->i = 0;
+ pos->cur = 0;
+ pos->cons = 0;
+ pos->e_old = 0;
+ pos->blocked_counter = 0;
+}
+