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/****************************************************************************
*
* Copyright (C) 2008-2012 PX4 Development Team. All rights reserved.
* Author: @author Laurens Mackay <mackayl@student.ethz.ch>
* @author Tobias Naegeli <naegelit@student.ethz.ch>
* @author Martin Rutschmann <rutmarti@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 control interface
*/
#include "pid.h"
__EXPORT void pid_init(PID_t *pid, float kp, float ki, float kd, float intmax,
uint8_t mode, uint8_t plot_i)
{
pid->kp = kp;
pid->ki = ki;
pid->kd = kd;
pid->intmax = intmax;
pid->mode = mode;
pid->plot_i = plot_i;
pid->count = 0;
pid->saturated = 0;
pid->sp = 0;
pid->error_previous = 0;
pid->integral = 0;
}
__EXPORT void pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float intmax)
{
pid->kp = kp;
pid->ki = ki;
pid->kd = kd;
pid->intmax = intmax;
// pid->mode = mode;
// pid->sp = 0;
// pid->error_previous = 0;
// pid->integral = 0;
}
//void pid_set(PID_t *pid, float sp)
//{
// pid->sp = sp;
// pid->error_previous = 0;
// pid->integral = 0;
//}
/**
*
* @param pid
* @param val
* @param dt
* @return
*/
__EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, float dt)
{
/* error = setpoint - actual_position
integral = integral + (error*dt)
derivative = (error - previous_error)/dt
output = (Kp*error) + (Ki*integral) + (Kd*derivative)
previous_error = error
wait(dt)
goto start
*/
float i, d;
pid->sp = sp;
float error = pid->sp - val;
if (pid->saturated && (pid->integral * error > 0)) {
//Output is saturated and the integral would get bigger (positive or negative)
i = pid->integral;
//Reset saturation. If we are still saturated this will be set again at output limit check.
pid->saturated = 0;
} else {
i = pid->integral + (error * dt);
}
// Anti-Windup. Needed if we don't use the saturation above.
if (pid->intmax != 0.0) {
if (i > pid->intmax) {
pid->integral = pid->intmax;
} else if (i < -pid->intmax) {
pid->integral = -pid->intmax;
} else {
pid->integral = i;
}
//Send Controller integrals
// Disabled because of new possibilities with debug_vect.
// Now sent in Main Loop at 5 Hz. 26.06.2010 Laurens
// if (pid->plot_i && (pid->count++ % 16 == 0)&&(global_data.param[PARAM_SEND_SLOT_DEBUG_2] == 1))
// {
// mavlink_msg_debug_send(MAVLINK_COMM_1, pid->plot_i, pid->integral);
// }
}
if (pid->mode == PID_MODE_DERIVATIV_CALC) {
d = (error - pid->error_previous) / dt;
} else if (pid->mode == PID_MODE_DERIVATIV_SET) {
d = -val_dot;
} else {
d = 0;
}
pid->error_previous = error;
return (error * pid->kp) + (i * pid->ki) + (d * pid->kd);
}
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