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Diffstat (limited to 'src/modules/systemlib/pid/pid.c')
| -rw-r--r-- | src/modules/systemlib/pid/pid.c | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/src/modules/systemlib/pid/pid.c b/src/modules/systemlib/pid/pid.c new file mode 100644 index 000000000..49315cdc9 --- /dev/null +++ b/src/modules/systemlib/pid/pid.c @@ -0,0 +1,191 @@ +/**************************************************************************** + * + * 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" +#include <math.h> + +__EXPORT void pid_init(PID_t *pid, float kp, float ki, float kd, float intmax, + float limit, uint8_t mode) +{ + pid->kp = kp; + pid->ki = ki; + pid->kd = kd; + pid->intmax = intmax; + pid->limit = limit; + pid->mode = mode; + pid->count = 0; + pid->saturated = 0; + pid->last_output = 0; + + pid->sp = 0; + pid->error_previous = 0; + pid->integral = 0; +} +__EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float intmax, float 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(intmax)) { + pid->intmax = intmax; + + } else { + ret = 1; + } + + if (isfinite(limit)) { + pid->limit = limit; + + } else { + ret = 1; + } + + return ret; +} + +//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 + */ + + if (!isfinite(sp) || !isfinite(val) || !isfinite(val_dot) || !isfinite(dt)) { + return pid->last_output; + } + + float i, d; + pid->sp = sp; + + // Calculated current error value + float error = pid->sp - val; + + if (isfinite(error)) { // Why is this necessary? DEW + pid->error_previous = error; + } + + // Calculate or measured current error derivative + + 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 = 0.0f; + } + + // Calculate the error integral and check for saturation + i = pid->integral + (error * dt); + + if (fabsf((error * pid->kp) + (i * pid->ki) + (d * pid->kd)) > pid->limit || + fabsf(i) > pid->intmax) { + i = pid->integral; // If saturated then do not update integral value + pid->saturated = 1; + + } else { + if (!isfinite(i)) { + i = 0; + } + + pid->integral = i; + pid->saturated = 0; + } + + // Calculate the output. Limit output magnitude to pid->limit + float output = (pid->error_previous * pid->kp) + (i * pid->ki) + (d * pid->kd); + + if (output > pid->limit) output = pid->limit; + + if (output < -pid->limit) output = -pid->limit; + + if (isfinite(output)) { + pid->last_output = output; + } + + + return pid->last_output; +} + + +__EXPORT void pid_reset_integral(PID_t *pid) +{ + pid->integral = 0; +} |