关于单片机PID的算法实现

转自 http://blog.163.com/djl_310/blog/static/8668667200872804916176/

用整型变量来实现PID算法，由于是用整型数来做的,所以也不是很精确,但是对于很多的使用场合,这个精度也够了，关于系数和采样电压全部是放大10倍处理的.所以精度不是很高. 但是也不是那么低,大部分的场合都够了. 实在觉得精度不够, 可以再放大10倍或者100倍处理,但是要注意不超出整个数据类型的范围就可以了.本程序包括PID计算和输出两部分.当偏差>10度全速加热,偏差在10度以内为PID计算输出.   具体的参考代码参见下面：
//================================================================
// pid.H
// Operation about PID algorithm procedure
// C51编译器 Keil 7.08
//================================================================
// 作者:zhoufeng
// Date :2007-08-06
// All rights reserved.
//================================================================

#include <reg52.h>
#include <intrins.h>
typedef   unsigned   char        uint8;      
typedef   unsigned   int         uint16;
typedef   unsigned   long int    uint32;
//  函数声明
void     PIDOutput ();
void     PIDOperation ();
//================================================================
typedef struct PIDValue
{
uint32      Ek_Uint32[3];                  //差值保存，给定和反馈的差值
uint8       EkFlag_Uint8[3];              //符号，1则对应的为负数，0为对应的为正数    
uint8       KP_Uint8;
uint8       KI_Uint8;
uint8       KD_Uint8;
uint16      Uk_Uint16;                 //上一时刻的控制电压
uint16      RK_Uint16;                //设定值
uint16      CK_Uint16;               //实际值
}PIDValueStr;
PIDValueStr PID;
uint8        out ;                 // 加热输出
uint8        count;               // 输出时间单位计数器
//================================================================
PID = Uk + KP*[E(k)-E(k-1)]+KI*E(k)+KD*[E(k)-2E(k-1)+E(k-2)];(增量型PID算式)
函数入口: RK(设定值),CK(实际值),KP,KI,KD
函数出口: U(K)
//PID运算函数
//================================================================
void     PIDOperation (void)
{
uint32       Temp[3];                                        //中间临时变量
uint32       PostSum;                                       //正数和
uint32       NegSum;                                       //负数和
Temp[0] = 0;
Temp[1] = 0;
Temp[2] = 0;
PostSum = 0;
NegSum = 0;
if( PID.RK_Uint16 > PID.CK_Uint16 )                    //设定值大于实际值否？
{
if( PID.RK_Uint16 - PID.CK_Uint16 >10 )            //偏差大于10否？
{
   PID.Uk_Uint16 = 100;    }                        //偏差大于10为上限幅值输出(全速加热)
else
{
   Temp[0] = PID.RK_Uint16 - PID.CK_Uint16;       //偏差<=10,计算E(k)
   PID.EkFlag_Uint8[1]=0;                        //E(k)为正数,因为设定值大于实际值
   //数值移位
      PID.Ek_Uint32[2] = PID.Ek_Uint32[1];
      PID.Ek_Uint32[1] = PID.Ek_Uint32[0];
      PID.Ek_Uint32[0] = Temp[0];
//================================================================
      if( PID.Ek_Uint32[0] >PID.Ek_Uint32[1] )                            //E(k)>E(k-1)否？
      {
Temp[0]=PID.Ek_Uint32[0] - PID.Ek_Uint32[1];           //E(k)>E(k-1)
        PID.EkFlag_Uint8[0]=0; }                                       //E(k)-E(k-1)为正数
   else
{
Temp[0]=PID.Ek_Uint32[0] - PID.Ek_Uint32[1];        //E(k)<E(k-1)
        PID.EkFlag_Uint8[0]=1; }                                          //E(k)-E(k-1)为负数

//================================================================
      Temp[2]=PID.Ek_Uint32[1]*2 ;                                             // 2E(k-1)
if( (PID.Ek_Uint32[0]+ PID.Ek_Uint32[2])>Temp[2] )            //E(k-2)+E(k)>2E(k-1)否？
      {
Temp[2]=(PID.Ek_Uint32[0]+ PID.Ek_Uint32[2])-Temp[2];     //E(k-2)+E(k)>2E(k-1)
        PID.EkFlag_Uint8[2]=0; }                                 //E(k-2)+E(k)-2E(k-1)为正数
   else
{
Temp[2]=Temp[2]-(PID.Ek_Uint32[0]+ PID.Ek_Uint32[2]); //E(k-2)+E(k)<2E(k-1)
        PID.EkFlag_Uint8[2]=1; }                                   //E(k-2)+E(k)-2E(k-1)为负数

//================================================================   
      Temp[0] = (uint32)PID.KP_Uint8 * Temp[0];                        // KP*[E(k)-E(k-1)]
      Temp[1] = (uint32)PID.KI_Uint8 * PID.Ek_Uint32[0];              // KI*E(k)
      Temp[2] = (uint32)PID.KD_Uint8 * Temp[2];                    // KD*[E(k-2)+E(k)-2E(k-1)]

 

//以下部分代码是讲所有的正数项叠加，负数项叠加 

//KP*[E(k)-E(k-1)]
if(PID.EkFlag_Uint8[0]==0)
PostSum += Temp[0];                                    //正数和
else                                             
NegSum += Temp[0];                                    //负数和

// KI*E(k)
if(PID.EkFlag_Uint8[1]==0)     
PostSum += Temp[1];                                 //正数和
else
   ;                                              //空操作，E(K)>0,因为设定值大于实际值

//KD*[E(k-2)+E(k)-2E(k-1)]                        

if(PID.EkFlag_Uint8[2]==0)
PostSum += Temp[2];                               //正数和
else
NegSum += Temp[2];                             //负数和

//U(K)                         
PostSum += (uint32)PID.Uk_Uint16;   
       
if(PostSum > NegSum )                         // 是否控制量为正数
{ Temp[0] = PostSum - NegSum;
if( Temp[0] < 100 )                         //小于上限幅值则为计算值输出
PID.Uk_Uint16 = (uint16)Temp[0];
else
PID.Uk_Uint16 = 100;                     //否则为上限幅值输出
}
else                                     //控制量输出为负数，则输出0(下限幅值输出)
   PID.Uk_Uint16 = 0;
}
}
else
{ PID.Uk_Uint16 = 0; }

}

//================================================================  
函数入口: U(K)
函数出口: out(加热输出)
//PID运算植输出函数
//================================================================  
void     PIDOutput (void)
{
static int i;
i=PID.Uk_Uint16;
if(i==0)
out=1;
else out=0;
if((count++)==5)//如定时中断为40MS,40MS*5=0.2S(输出时间单位),加热周期20S(100等份)
{              //每20S PID运算一次
count=0;
i--;
}
}