硬件原理:加热电阻为400,电源为市电,固态继电器控制通断,并提取市电的过零信号,单片机采用mega48,继电器通断最小时间为10ms,通断PWM的周期为100个过零信号.

本程序采用绝对式PID算法,当温度相差很多时,采用P算法(比例算法),当到达设定温度时,采用PID算法,实际实用稳定性还可以,上下波动在0.5度以内.

#include

#include "PID.h"

//static PID sPID;

//static PID *sptr=&sPID;

TADD Tadd1;

TADD Tadd2;

void IncPIDInit(PID *sptr)

{

sptr->SumError=0;

sptr->LastError=0;

sptr->PrevError=0;

//sptr->Proportion = 900;

//sptr->Integral=20;

//sptr->Derivative = 2;

//sptr->SetPoint = 0;

}

typedef struct

{

int SetPoint; //设定目标值

int32_t SumError; //误差累计

//int Proportion;

//int Integral; //积分常数

//int Derivative; //微分常数

int LastError; //Error[-1]

int PrevError; //Error[-2]

}PID;

#define PID_Proportion 900 //比例常数

#define PID_Integral 20 //积分常数

#define PID_Derivative 2 //微分常数

#define PWM_T 100

#define MAX_T 80 //加热的最大温度

typedef struct

{

PID spid; //PID控制器

unsigned char pwm_H;//输出

unsigned char EnAdd;//加热使能

int real_T; //实际温度值

unsigned char Taddset[3]; //加热的设定温度

unsigned char set_NO; //加热的档数

unsigned char errorflg;

unsigned char addokflg;

}TADD;

void LocPIDCalc(TADD *sptr)

{

int iError,dError;

int32_t result;

iError = (sptr->spid.SetPoint*4) - (sptr->real_T/4);

//sptr->spid.LastError = iError;

if(iError>-2&&iError<4)

{

sptr->addokflg=1;

sptr->spid.SumError +=iError;

dError = iError-sptr->spid.LastError;

sptr->spid.LastError = iError;

result=(PID_Proportion * iError +

PID_Integral * sptr->spid.SumError +

PID_Derivative * dError)/20;

}

else

{

sptr->spid.SumError =0;

sptr->spid.LastError=0;

if(iError>0)

sptr->addokflg=0;

result=(PID_Proportion * iError)/20;

}

if(result>PWM_T)

result=PWM_T;

else if(result<0)

result=0;

if((sptr->real_T>>4)>MAX_T||sptr->errorflg==0)

result=0;

sptr->pwm_H=(unsigned char) result;

//return (unsigned char) result;

}