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PID C++ implementation
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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
@vtellier

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@vtellier vtellier commented Jan 30, 2017

Thanks a lot!

I would just suggest to check the Dt term as it might lead to a division per zero:

if(dt == 0.0)
    throw std::exception("Impossible to create a PID regulator with a null loop interval time.");
@AGenchev

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@AGenchev AGenchev commented Dec 2, 2017

It works - nice :) :+1 . Now it's a good starting point for speed optimization like fixed point implementation for FPU-less MCUs.

@Tbone2401

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@Tbone2401 Tbone2401 commented Aug 12, 2018

Can I ask why you decided to create 2 classes for this?
I don't know the in and outs of c++, but I'm wondering :)

@nullbus

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@nullbus nullbus commented Sep 5, 2018

@Tbone2401 It is called PImpl. See https://en.cppreference.com/w/cpp/language/pimpl for more information :)

@LiuJungle

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@LiuJungle LiuJungle commented Dec 2, 2018

nice, it is a good tutorial to learn the C++ implementation of pid controller.

@brztitouan

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@brztitouan brztitouan commented Feb 13, 2019

Hello, dt value is in ms ? or in second ? Thank you

@qiweiyang2018

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@qiweiyang2018 qiweiyang2018 commented Apr 18, 2019

@brztitouan That depends on your own situation. If you use s or ms, just scale all other parameters accordingly.

@Purpleshadz

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@Purpleshadz Purpleshadz commented May 2, 2019

I am struggling to find the cmath header. Where could I find this file?

@oldrev

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@oldrev oldrev commented Jul 25, 2019

Hello, I did a fixed-point version:

My Gist

@EserFromCambridge

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@EserFromCambridge EserFromCambridge commented Sep 17, 2019

Hello,
May I ask the license of this library if you don't mind ?

@chris-praxis

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@chris-praxis chris-praxis commented Oct 30, 2019

Maybe "dt" should be passed in to calculate since it's likely to change at least slightly.

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Owner Author

@bradley219 bradley219 commented Nov 18, 2019

Hello,
May I ask the license of this library if you don't mind ?

added license to source files

@Ramkrishnamaurya

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@Ramkrishnamaurya Ramkrishnamaurya commented Jul 23, 2020

what is dt

@Ramkrishnamaurya

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@Ramkrishnamaurya Ramkrishnamaurya commented Jul 23, 2020

or how to calculate it

@currentleak

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@currentleak currentleak commented Aug 3, 2020

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

@roboticsai

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@roboticsai roboticsai commented Oct 16, 2020

how to use this inside a class? how to initialize the pid object inside the constructor of another class?

@ngjermundshaug

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@ngjermundshaug ngjermundshaug commented Oct 23, 2020

Nice work! Some ideas for minor improvements:

  • Add support for passing dt as an optional parameter to calculate - like mentioned by others.
  • Add support for ReverseActing - e.g. where Brakes needs to be increased to decrease vehicle speed
    error = reverseActing ? (pv-setpoint) : (setpoint - pv)
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