thermferm/pid.c

/*****************************************************************************
 * Copyright (C) 2015
 *   
 * Michiel Broek <mbroek at mbse dot eu>
 *
 * This file is part of the mbsePi-apps
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * mbsePi-apps is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with ThermFerm; see the file COPYING.  If not, write to the Free
 * Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *****************************************************************************/

#include "thermferm.h"
#include "pid.h"


void InitPID(pid_var *pid, int type)
{
    pid->Err = pid->ErrLast = pid->iState = 0.0;
    pid->Input = pid->OutP = pid->SetP = 0.0;
    pid->pGain = pid->iGain = pid->dGain = 0.0;
    pid->idleRange = 0.4;
    pid->Mode = PID_MODE_NONE;
    pid->Type = type;
    pid->iMax = 100.0;
}


void UpdatePID(pid_var *pid)
{
    if (pid->Mode == PID_MODE_AUTO) {

	double	pTerm, dTerm, iTerm;

	if (pid->Type == PID_TYPE_HEAT)
	    pid->Err = pid->SetP - pid->Input;
	else
	    pid->Err = pid->Input - pid->SetP;

	/*
	 * Calculate the integral state with appopriate limiting.
	 * Use ErrLastLast as iState
	 */
	pid->iState += pid->Err;
	if (pid->iState > PID_WINDUP_GUARD)
	    pid->iState = PID_WINDUP_GUARD;
	else if (pid->iState < -PID_WINDUP_GUARD)
	    pid->iState = -PID_WINDUP_GUARD;

	pTerm = pid->pGain * pid->Err;
	iTerm = pid->iGain * pid->iState;
	dTerm = pid->dGain * (pid->Err - pid->ErrLast);

	pid->OutP = pTerm + dTerm + iTerm;
	pid->ErrLast = pid->Err;

    } else if (pid->Mode == PID_MODE_BOO) {
	/*
	 * Mode Bang On Off
	 */
	pid->ErrLast = pid->Err;

	if (pid->Type == PID_TYPE_HEAT)
	    pid->Err = pid->SetP - pid->Input;
	else
	    pid->Err = pid->Input - pid->SetP;

	if (pid->OutP && (pid->Err <= 0.0))
	    pid->OutP = 0.0;
	else if ((pid->OutP == 0.0) && (pid->Err > pid->idleRange))
	    pid->OutP = pid->iMax;

	pid->iState = 0.0;

    } else {
	/*
	 * While in manual mode, stay ready for bumpless switch to
	 * auto.
	 */
	pid->ErrLast = pid->Err = 0.0;
	pid->OutP = pid->iState = 0.0;
    }

    if (pid->OutP > pid->iMax)
	pid->OutP = pid->iMax;
    if (pid->OutP < 0.0)
	pid->OutP = 0.0;

}