/****************************************************************************
*
* Copyright (C) 2008-2013 PX4 Development Team. All rights reserved.
* Author: Laurens Mackay <mackayl@student.ethz.ch>
* Tobias Naegeli <naegelit@student.ethz.ch>
* Martin Rutschmann <rutmarti@student.ethz.ch>
* Anton Babushkin <anton.babushkin@me.com>
* Julian Oes <joes@student.ethz.ch>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file pid.c
*
* Implementation of generic PID controller.
*
* @author Laurens Mackay <mackayl@student.ethz.ch>
* @author Tobias Naegeli <naegelit@student.ethz.ch>
* @author Martin Rutschmann <rutmarti@student.ethz.ch>
* @author Anton Babushkin <anton.babushkin@me.com>
* @author Julian Oes <joes@student.ethz.ch>
*/
#include "pid.h"
#include <math.h>
#define SIGMA 0.000001f
__EXPORT void pid_init(PID_t *pid, uint8_t mode, float dt_min)
{
pid->mode = mode;
pid->dt_min = dt_min;
pid->kp = 0.0f;
pid->ki = 0.0f;
pid->kd = 0.0f;
pid->integral = 0.0f;
pid->integral_limit = 0.0f;
pid->output_limit = 0.0f;
pid->error_previous = 0.0f;
pid->last_output = 0.0f;
}
__EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float integral_limit, float output_limit)
{
int ret = 0;
if (isfinite(kp)) {
pid->kp = kp;
} else {
ret = 1;
}
if (isfinite(ki)) {
pid->ki = ki;
} else {
ret = 1;
}
if (isfinite(kd)) {
pid->kd = kd;
} else {
ret = 1;
}
if (isfinite(integral_limit)) {
pid->integral_limit = integral_limit;
} else {
ret = 1;
}
if (isfinite(output_limit)) {
pid->output_limit = output_limit;
} else {
ret = 1;
}
return ret;
}
__EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, float dt)
{
if (!isfinite(sp) || !isfinite(val) || !isfinite(val_dot) || !isfinite(dt)) {
return pid->last_output;
}
float i, d;
/* current error value */
float error = sp - val;
/* current error derivative */
if (pid->mode == PID_MODE_DERIVATIV_CALC) {
d = (error - pid->error_previous) / fmaxf(dt, pid->dt_min);
pid->error_previous = error;
} else if (pid->mode == PID_MODE_DERIVATIV_CALC_NO_SP) {
d = (-val - pid->error_previous) / fmaxf(dt, pid->dt_min);
pid->error_previous = -val;
} else if (pid->mode == PID_MODE_DERIVATIV_SET) {
d = -val_dot;
} else {
d = 0.0f;
}
if (!isfinite(d)) {
d = 0.0f;
}
/* calculate PD output */
float output = (error * pid->kp) + (d * pid->kd);
if (pid->ki > SIGMA) {
// Calculate the error integral and check for saturation
i = pid->integral + (error * dt);
/* check for saturation */
if (isfinite(i)) {
if ((pid->output_limit < SIGMA || (fabsf(output + (i * pid->ki)) <= pid->output_limit)) &&
fabsf(i) <= pid->integral_limit) {
/* not saturated, use new integral value */
pid->integral = i;
}
}
/* add I component to output */
output += pid->integral * pid->ki;
}
/* limit output */
if (isfinite(output)) {
if (pid->output_limit > SIGMA) {
if (output > pid->output_limit) {
output = pid->output_limit;
} else if (output < -pid->output_limit) {
output = -pid->output_limit;
}
}
pid->last_output = output;
}
return pid->last_output;
}
__EXPORT void pid_reset_integral(PID_t *pid)
{
pid->integral = 0.0f;
}
