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/** | |
* Copyright 2019 Bradley J. Snyder <snyder.bradleyj@gmail.com> | |
* | |
* 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. | |
*/ | |
#ifndef _PID_SOURCE_ | |
#define _PID_SOURCE_ | |
#include <iostream> | |
#include <cmath> | |
#include "pid.h" | |
using namespace std; | |
class PIDImpl | |
{ | |
public: | |
PIDImpl( double dt, double max, double min, double Kp, double Kd, double Ki ); | |
~PIDImpl(); | |
double calculate( double setpoint, double pv ); | |
private: | |
double _dt; | |
double _max; | |
double _min; | |
double _Kp; | |
double _Kd; | |
double _Ki; | |
double _pre_error; | |
double _integral; | |
}; | |
PID::PID( double dt, double max, double min, double Kp, double Kd, double Ki ) | |
{ | |
pimpl = new PIDImpl(dt,max,min,Kp,Kd,Ki); | |
} | |
double PID::calculate( double setpoint, double pv ) | |
{ | |
return pimpl->calculate(setpoint,pv); | |
} | |
PID::~PID() | |
{ | |
delete pimpl; | |
} | |
/** | |
* Implementation | |
*/ | |
PIDImpl::PIDImpl( double dt, double max, double min, double Kp, double Kd, double Ki ) : | |
_dt(dt), | |
_max(max), | |
_min(min), | |
_Kp(Kp), | |
_Kd(Kd), | |
_Ki(Ki), | |
_pre_error(0), | |
_integral(0) | |
{ | |
} | |
double PIDImpl::calculate( double setpoint, double pv ) | |
{ | |
// Calculate error | |
double error = setpoint - pv; | |
// Proportional term | |
double Pout = _Kp * error; | |
// Integral term | |
_integral += error * _dt; | |
double Iout = _Ki * _integral; | |
// Derivative term | |
double derivative = (error - _pre_error) / _dt; | |
double Dout = _Kd * derivative; | |
// Calculate total output | |
double output = Pout + Iout + Dout; | |
// Restrict to max/min | |
if( output > _max ) | |
output = _max; | |
else if( output < _min ) | |
output = _min; | |
// Save error to previous error | |
_pre_error = error; | |
return output; | |
} | |
PIDImpl::~PIDImpl() | |
{ | |
} | |
#endif |
/** | |
* Copyright 2019 Bradley J. Snyder <snyder.bradleyj@gmail.com> | |
* | |
* 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. | |
*/ | |
#ifndef _PID_H_ | |
#define _PID_H_ | |
class PIDImpl; | |
class PID | |
{ | |
public: | |
// Kp - proportional gain | |
// Ki - Integral gain | |
// Kd - derivative gain | |
// dt - loop interval time | |
// max - maximum value of manipulated variable | |
// min - minimum value of manipulated variable | |
PID( double dt, double max, double min, double Kp, double Kd, double Ki ); | |
// Returns the manipulated variable given a setpoint and current process value | |
double calculate( double setpoint, double pv ); | |
~PID(); | |
private: | |
PIDImpl *pimpl; | |
}; | |
#endif |
/** | |
* Copyright 2019 Bradley J. Snyder <snyder.bradleyj@gmail.com> | |
* | |
* 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" | |
#include <stdio.h> | |
int main() { | |
PID pid = PID(0.1, 100, -100, 0.1, 0.01, 0.5); | |
double val = 20; | |
for (int i = 0; i < 100; i++) { | |
double inc = pid.calculate(0, val); | |
printf("val:% 7.3f inc:% 7.3f\n", val, inc); | |
val += inc; | |
} | |
return 0; | |
} |
To compile library: | |
g++ -c pid.cpp -o pid.o | |
To compile example code: | |
g++ pid_example.cpp pid.o -o pid_example | |
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It works - nice :) :+1 . Now it's a good starting point for speed optimization like fixed point implementation for FPU-less MCUs. |
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Can I ask why you decided to create 2 classes for this? |
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@Tbone2401 It is called PImpl. See https://en.cppreference.com/w/cpp/language/pimpl for more information :) |
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nice, it is a good tutorial to learn the C++ implementation of pid controller. |
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Hello, dt value is in ms ? or in second ? Thank you |
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@brztitouan That depends on your own situation. If you use s or ms, just scale all other parameters accordingly. |
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I am struggling to find the cmath header. Where could I find this file? |
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Hello, I did a fixed-point version: |
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Hello, |
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Maybe "dt" should be passed in to calculate since it's likely to change at least slightly. |
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added license to source files |
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what is dt |
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or how to calculate it |
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dt is the time between 2 latest PV reading (and/or Command setting), guess the first value then read a timer at every loop count Very nice! thanks @bradley219 |
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how to use this inside a class? how to initialize the pid object inside the constructor of another class? |
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Nice work! Some ideas for minor improvements:
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Excellent solution. It worked really nice for our purposes. Thanks for your support to the community |
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Thanks a lot!
I would just suggest to check the
Dt
term as it might lead to a division per zero: