51单片机实现PID算法（温度控制）

//================================================================
// 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
#include
typedef   unsigned   char        uint8;       
typedef   unsigned   int         uint16;  
typedef   unsigned   long int    uint32; 

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

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
   //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)         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)]

     

if(PID.EkFlag_Uint8[0]==0)
  PostSum = Temp[0];                                    //正数和
else                                              
  NegSum = Temp[0];                                    //负数和
 
if(PID.EkFlag_Uint8[1]==0)      
  PostSum = Temp[1];                                 //正数和
else
   ;                                                 //空操作，E(K)>0
                           
if(PID.EkFlag_Uint8[2]==0)
PostSum = Temp[2];                               //正数和
else
  NegSum = Temp[2];                             //负数和
                             
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;  } 

}

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--;
}
}