用整型變量來(lái)實(shí)現(xiàn)PID算法，由于是用整型數(shù)來(lái)做的,所以也不是很精確,但是對(duì)于很多的使用場(chǎng)合,這個(gè)精度也夠了，關(guān)于系數(shù)和采樣電壓全部是放大10倍處理的.所以精度不是很高. 但是也不是那么低,大部分的場(chǎng)合都?jí)蛄? 實(shí)在覺得精度不夠, 可以再放大10倍或者100倍處理,但是要注意不超出整個(gè)數(shù)據(jù)類型的范圍就可以了.本程序包括PID計(jì)算和輸出兩部分.當(dāng)偏差>10度全速加熱,偏差在10度以內(nèi)為PID計(jì)算輸出.  

 具體的參考代碼參見下面：

*/
//================================================================
// pid.H
// Operation about PID algorithm procedure
// C51編譯器  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;
/**********函數(shù)聲明************/
void     PIDOutput ();
void     PIDOperation ();
/*****************************/
typedef struct PIDValue
{
uint32      Ek_Uint32[3];                  //差值保存，給定和反饋的差值
uint8       EkFlag_Uint8[3];              //符號(hào)，1則對(duì)應(yīng)的為負(fù)數(shù)，0為對(duì)應(yīng)的為正數(shù)    
uint8       KP_Uint8;
uint8       KI_Uint8;
uint8       KD_Uint8;
uint16      Uk_Uint16;                 //上一時(shí)刻的控制電壓
uint16      RK_Uint16;                //設(shè)定值
uint16      CK_Uint16;               //實(shí)際值
}PIDValueStr;
PIDValueStr  PID;
uint8        out ;                 // 加熱輸出
uint8        count;               // 輸出時(shí)間單位計(jì)數(shù)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)
函數(shù)入口: RK(設(shè)定值),CK(實(shí)際值),KP,KI,KD
函數(shù)出口: U(K)
//PID運(yùn)算函數(shù)
********************************/
void     PIDOperation (void) 
{
uint32       Temp[3];                                        //中間臨時(shí)變量
uint32       PostSum;                                       //正數(shù)和
uint32       NegSum;                                       //負(fù)數(shù)和
Temp[0] = 0;
Temp[1] = 0;
Temp[2] = 0;
PostSum = 0;
NegSum  = 0;
if( PID.RK_Uint16 > PID.RK_Uint16 )                    //設(shè)定值大于實(shí)際值否？
{
  if( PID.RK_Uint16 - PID.RK_Uint16 >10 )            //偏差大于10否？
  {
   PID.Uk_Uint16 = 100;    }                        //偏差大于10為上限幅值輸出(全速加熱)
  else
  {
   Temp[0] = PID.RK_Uint16 - PID.CK_Uint16;       //偏差<=10,計(jì)算E(k)
   PID.EkFlag_Uint8[1]=0;                        //E(k)為正數(shù)
   //數(shù)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)為正數(shù)
   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)為負(fù)數(shù)
/****************************************/
      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)為正數(shù)
   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)為負(fù)數(shù)
/****************************************/      
      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)]

/*以下部分代碼是講所有的正數(shù)項(xiàng)疊加，負(fù)數(shù)項(xiàng)疊加*/    
/**********KP*[E(k)-E(k-1)]**********/
if(PID.EkFlag_Uint8[0]==0)
  PostSum  = Temp[0];                                    //正數(shù)和
else                                             
  NegSum  = Temp[0];                                    //負(fù)數(shù)和
/********* KI*E(k)****************/
if(PID.EkFlag_Uint8[1]==0)     
  PostSum  = Temp[1];                                 //正數(shù)和
else
   ;                                                 //空操作，E(K)>0
/****KD*[E(k-2) E(k)-2E(k-1)]****/                          
if(PID.EkFlag_Uint8[2]==0)
PostSum  = Temp[2];                               //正數(shù)和
else
  NegSum  = Temp[2];                             //負(fù)數(shù)和
/***************U(K)***************/                            
PostSum  = (uint32)PID.Uk_Uint16;   
       
if(PostSum > NegSum )                         // 是否控制量為正數(shù)
{ Temp[0] = PostSum - NegSum;
if( Temp[0] < 100 )                         //小于上限幅值則為計(jì)算值輸出
PID.Uk_Uint16 = (uint16)Temp[0];
else
  PID.Uk_Uint16 = 100;                     //否則為上限幅值輸出
}
else                                     //控制量輸出為負(fù)數(shù)，則輸出0(下限幅值輸出)
   PID.Uk_Uint16 = 0;
}
}
else
{ PID.Uk_Uint16 = 0;  }

}

/*********************************
函數(shù)入口: U(K)
函數(shù)出口: out(加熱輸出)
//PID運(yùn)算植輸出函數(shù)
********************************/
void     PIDOutput (void) 
{
static  int i;
i=PID.Uk_Uint16;
if(i==0)
  out=1;
else out=0;
if((count  )==5)//如定時(shí)中斷為40MS,40MS*5=0.2S(輸出時(shí)間單位),加熱周期20S(100等份)
{              //每20S PID運(yùn)算一次
  count=0;
  i--;
}
}