Pozdrav, nisam detaljno sve procitao, vec delove...
Uglavnom ne pokusavam da realizujem PID regulator u digitalnoj tehnici, vec algoritam za odredjivanje parametara PID-a, konkretno ZN metodu.
Pronasao sam arduino biblioteku sa ovim algoritmom, i delimicno objasnjenje. Biblioteka je zasnovana na simulink modelu...
Code:
#if ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif
#include <PID_AutoTune_v0.h>
PID_ATune::PID_ATune(double* Input, double* Output)
{
input = Input;
output = Output;
controlType =0 ; //default to PI
noiseBand = 0.5;
running = false;
oStep = 30;
SetLookbackSec(10);
lastTime = millis();
}
void PID_ATune::Cancel()
{
running = false;
}
int PID_ATune::Runtime()
{
justevaled=false;
if(peakCount>9 && running)
{
running = false;
FinishUp();
return 1;
}
unsigned long now = millis();
if((now-lastTime)<sampleTime) return false;
lastTime = now;
double refVal = *input;
justevaled=true;
if(!running)
{ //initialize working variables the first time around
peakType = 0;
peakCount=0;
justchanged=false;
absMax=refVal;
absMin=refVal;
setpoint = refVal;
running = true;
outputStart = *output;
*output = outputStart+oStep;
}
else
{
if(refVal>absMax)absMax=refVal;
if(refVal<absMin)absMin=refVal;
}
//oscillate the output base on the input's relation to the setpoint
if(refVal>setpoint+noiseBand) *output = outputStart-oStep;
else if (refVal<setpoint-noiseBand) *output = outputStart+oStep;
//bool isMax=true, isMin=true;
isMax=true;isMin=true;
//id peaks
for(int i=nLookBack-1;i>=0;i--)
{
double val = lastInputs[i];
if(isMax) isMax = refVal>val;
if(isMin) isMin = refVal<val;
lastInputs[i+1] = lastInputs[i];
}
lastInputs[0] = refVal;
if(nLookBack<9)
{ //we don't want to trust the maxes or mins until the inputs array has been filled
return 0;
}
if(isMax)
{
if(peakType==0)peakType=1;
if(peakType==-1)
{
peakType = 1;
justchanged=true;
peak2 = peak1;
}
peak1 = now;
peaks[peakCount] = refVal;
}
else if(isMin)
{
if(peakType==0)peakType=-1;
if(peakType==1)
{
peakType=-1;
peakCount++;
justchanged=true;
}
if(peakCount<10)peaks[peakCount] = refVal;
}
if(justchanged && peakCount>2)
{ //we've transitioned. check if we can autotune based on the last peaks
double avgSeparation = (abs(peaks[peakCount-1]-peaks[peakCount-2])+abs(peaks[peakCount-2]-peaks[peakCount-3]))/2;
if( avgSeparation < 0.05*(absMax-absMin))
{
FinishUp();
running = false;
return 1;
}
}
justchanged=false;
return 0;
}
void PID_ATune::FinishUp()
{
*output = outputStart;
//we can generate tuning parameters!
Ku = 4*(2*oStep)/((absMax-absMin)*3.14159);
Pu = (double)(peak1-peak2) / 1000;
}
double PID_ATune::GetKp()
{
return controlType==1 ? 0.6 * Ku : 0.4 * Ku;
}
double PID_ATune::GetKi()
{
return controlType==1? 1.2*Ku / Pu : 0.48 * Ku / Pu; // Ki = Kc/Ti
}
double PID_ATune::GetKd()
{
return controlType==1? 0.075 * Ku * Pu : 0; //Kd = Kc * Td
}
void PID_ATune::SetOutputStep(double Step)
{
oStep = Step;
}
double PID_ATune::GetOutputStep()
{
return oStep;
}
void PID_ATune::SetControlType(int Type) //0=PI, 1=PID
{
controlType = Type;
}
int PID_ATune::GetControlType()
{
return controlType;
}
void PID_ATune::SetNoiseBand(double Band)
{
noiseBand = Band;
}
double PID_ATune::GetNoiseBand()
{
return noiseBand;
}
void PID_ATune::SetLookbackSec(int value)
{
if (value<1) value = 1;
if(value<25)
{
nLookBack = value * 4;
sampleTime = 250;
}
else
{
nLookBack = 100;
sampleTime = value*10;
}
}
int PID_ATune::GetLookbackSec()
{
return nLookBack * sampleTime / 1000;
}
Podesavanje PID parametara primenom Ziegler-Nichols metode
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