bradley219 · September 30, 2025 04:42 · vtellier · Jan 30, 2017 · AGenchev · Dec 2, 2017
diff --git a/.gitignore b/.gitignore
 .DS_Store
diff --git a/pid.cpp b/pid.cpp
 /**
 * Copyright 2019 Bradley J. Snyder <[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.
 */

 #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
diff --git a/pid.h b/pid.h
 /**
 * Copyright 2019 Bradley J. Snyder <[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.
 */

 #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
diff --git a/pid_example.cpp b/pid_example.cpp
 /**
 * Copyright 2019 Bradley J. Snyder <[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"
 #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;
 }
diff --git a/pid_README b/pid_README
 To compile library:
 g++ -c pid.cpp -o pid.o

 To compile example code:
 g++ pid_example.cpp pid.o -o pid_example
	/**
	* Copyright 2019 Bradley J. Snyder <[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.
	*/

	#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
	To compile library:
	g++ -c pid.cpp -o pid.o

	To compile example code:
	g++ pid_example.cpp pid.o -o pid_example