105 lines
2.3 KiB
C
105 lines
2.3 KiB
C
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/**
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* @file pi.c
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* @brief Implements a Proportional Integral clock servo.
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* @note Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <stdlib.h>
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#include "pi.h"
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#include "servo_private.h"
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#define KP 0.7
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#define KI 0.3
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struct pi_servo {
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struct servo servo;
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double offset[2];
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double local[2];
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double drift;
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double maxppb;
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int count;
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};
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static void pi_destroy(struct servo *servo)
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{
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struct pi_servo *s = container_of(servo, struct pi_servo, servo);
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free(s);
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}
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static double pi_sample(struct servo *servo,
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double offset,
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double local_ts,
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enum servo_state *state)
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{
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double ki_term, ppb = 0.0;
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struct pi_servo *s = container_of(servo, struct pi_servo, servo);
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switch (s->count) {
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case 0:
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s->offset[0] = offset;
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s->local[0] = local_ts;
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*state = SERVO_UNLOCKED;
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s->count = 1;
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break;
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case 1:
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s->offset[1] = offset;
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s->local[1] = local_ts;
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*state = SERVO_UNLOCKED;
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s->count = 2;
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break;
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case 2:
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s->drift = (s->offset[1] - s->offset[0]) /
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(s->local[1] - s->local[0]);
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*state = SERVO_UNLOCKED;
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s->count = 3;
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break;
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case 3:
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*state = SERVO_JUMP;
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s->count = 4;
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break;
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case 4:
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ki_term = KI * offset;
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ppb = KP * offset + s->drift + ki_term;
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if (ppb < -s->maxppb) {
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ppb = -s->maxppb;
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} else if (ppb > s->maxppb) {
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ppb = s->maxppb;
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} else {
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s->drift += ki_term;
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}
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*state = SERVO_LOCKED;
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break;
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}
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return ppb;
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}
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struct servo *pi_servo_create(int max_ppb)
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{
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struct pi_servo *s;
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s = calloc(1, sizeof(*s));
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if (!s)
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return NULL;
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s->servo.destroy = pi_destroy;
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s->servo.sample = pi_sample;
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s->maxppb = max_ppb;
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return &s->servo;
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}
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