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pid.cpp
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pid.cpp
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/* File: pid.cpp
* Pid contains a class for easy PID control. Based on AVR221.
*/
/* Copyright (c) 2012-2013 Domen Ipavec ([email protected])
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "pid.h"
avr_cpp_lib::Pid::Pid(int16_t p, int16_t i, int16_t d, int16_t min, int16_t max)
: sumError(0), lastProcessValue(0),
P_Factor(p), I_Factor(i), D_Factor(d),
maxError(MAX_INT / (p + 1)), maxSumError(MAX_I_TERM / (i + 1)),
minRet(min), maxRet(max) {
}
int16_t avr_cpp_lib::Pid::controller(PidData pd) {
int16_t error, p_term;
int32_t i_term, ret, temp;
error = pd.setPoint - pd.processValue;
// Calculate Pterm and limit error overflow
if (error > this->maxError) {
p_term = MAX_INT;
} else if (error < -this->maxError) {
p_term = -MAX_INT;
} else {
p_term = this->P_Factor * error;
}
// Calculate Iterm and limit integral runaway
temp = this->sumError + error;
if (temp > this->maxSumError) {
i_term = MAX_I_TERM;
this->sumError = this->maxSumError;
} else if (temp < -this->maxSumError) {
i_term = -MAX_I_TERM;
this->sumError = -this->maxSumError;
} else {
this->sumError = temp;
i_term = this->I_Factor * this->sumError;
}
// Calculate d-term and combine
ret = (p_term + i_term + this->D_Factor * (this->lastProcessValue - pd.processValue)) >> SCALING_FACTOR;
this->lastProcessValue = pd.processValue;
if (ret > this->maxRet) {
return this->maxRet;
}
if (ret < this->minRet) {
return this->minRet;
}
return ((int16_t)ret);
}