单片机PID算法实现

initial interrupter                
void init_interrupter(void) 
{ 
TMOD=0x21; /* 设置计时器0工作于模式1，设置计时器1工作于模式2*/ 
TL0=0x00;    /* T0=0000定时时间为71.1ms;71.1ms*15＝1.066s*/ 
TH0=0xdc;    /*T0=DC00定时时间为10ms;10ms*100＝1s*/ /*T0=FC66定时时间为1ms;10ms*1000＝1s*/ 
TL1=0xfd;    /* 设置串口通信速率9600bps*/ 
TH1=0xfd; 
PCON=0x00; /* SMOD=0, 速率不倍增*/ 
SCON=0x50; /* 8位数据通信，串行通信方式1，允许单片机接收数据*/ 
IP=0x10;    /*serial com is preferential*/ 
IE=0x92;    /* 定时器0, 串口中断允许;定时器1中断禁止*/ 
rs485_receive=0; 
rs485_transmitte=0; 
TR0=1;      /* 启动定时器0*/ 
TR1=1;      /* 启动定时器1*/ 
} 
void timer0_server(void) interrupt 1 using 1 /**/ 
{ 
   TL0=0x00; TH0=0xdc;/*T0=DC00 timing interval is 10ms;10ms*100＝1s*/ /*T0=FC66 timing interval is 1ms;10ms*1000＝1s*/ 
   if (flag_serial==1) 
   { 
     timer0_counter_3++; 
     if (timer0_counter_3>11) 
     { 
         timer0_counter_3=0; 
         flag_serial=0; 
         pointer_serial_com_data=serial_com_data; 
         counter_serial_com_data=0; 
     } 
   } 
   dog=!dog;/*Timer0 is full(10ms), feed dog*/ 
   if (timing_interval==0) {timing_interval=1;} /*timing_interval is lost then set it to 1 second*/ 
   timer0_counter_1++;/*timer0_counter_1 is software timer. when timer0 interrupt is full, it increase automatically*/ 
   if ((unsigned char) (timer0_counter_1/100)==timing_interval) /*timing_interval arrives*/ 
   { 
     out_flag=1;/*indexing 占空比 high level begin*/ 
     /*-scan 0809 to get current equipment's temperature-*/ 
     scan_current_Temperature(); 
     origina_address=0x82; 
     display1_Temperature(current_Temperature,origina_address); 
     /*-calculate out_value-*/ 
     PID_algorithm_function(PID_mode,PP,II,DD,BB,current_Temperature,seted_temperature); 
     //out_value=0.5; 
     if (out_value>0.0) /*out_value=0.0, then 占空比 is zero*/ 
     { 
         control_0=1; 
         ledctrl_address=0x8c; 
         leddata_address=0xff; 
     } 
     //reset timer0_counter_1 and timer0_counter_2, 
     timer0_counter_1=0; //indexing timing_interval's timing 
     timer0_counter_2=0; //indexing 占空比's timing 
   } 
   if(out_flag==1) 
   { 
     timer0_counter_2++; 
     if (out_value<1.0) 
     { 
         if( (unsigned char) (timer0_counter_2/out_value/100) >= timing_interval) 
         { 
           timer0_counter_2=0; 
           control_0=0; 
           ledctrl_address=0x8c; 
           leddata_address=0x00; 
           out_flag=0; 
         } 
     } 
   } 
} 


float PID_algorithm_function(uchar PID_mode_2,float P_2,I_2,D_2,B_2,current_Temperature_2,seted_temperature_2) 
{ 
   float idata delta; 
   switch (PID_mode_2) 
   { 
     case 1: break;/*PID mode*/ 
     case 2: D_2=0;      break;/*PI mode*/ 
     case 3: I_2=0;      break;/*PD mode*/ 
     case 4: I_2=0; D_2=0; break;/*P mode*/ 
   } 
   if (PID_mode_2<5)/*PID algorithm*/ 
    ek=(seted_temperature_2-current_Temperature_2)/99.9; 
     delta=P_2*(ek-ek1)+I_2*ek+D_2*(ek-2.0*ek1+ek2); 
     out_value=out_value+delta; 
     ek2=ek1; 
     ek1=ek; 
     if (out_value>1.0) 
     { 
         out_value=1; 
     } 
     else if (out_value<=0) 
     { 
         out_value=0.0; 
     } 
   if (PID_mode_2==5) /*BB algorithm*/ 
   { 
     if (current_Temperature_2-seted_temperature_2>=B_2) {out_value=0.0;} 
     if (seted_temperature_2-current_Temperature_2>=B_2) {out_value=1.0;} 
   } 
   return (out_value);