此系统是基于PID的单片机温度控制系统，我在网上搜到一段完整的程序，并按他的程序做出了相应的proteus硬件仿真，但
是并没有达到预期的效果.待提高。

程序如下：

#include＜reg51.h> 
#include＜intrins.h> 
#include＜math.h> 
#include＜string.h> 
struct PID { 
unsigned int SetPoint; // 设定目标 Desired Value 
unsigned int Proportion; // 比例常数 Proportional Const 
unsigned int Integral; // 积分常数 Integral Const 
unsigned int Derivative; // 微分常数 Derivative Const 
unsigned int LastError; // Error[-1] 
unsigned int PrevError; // Error[-2] 
unsigned int SumError; // Sums of Errors 
}; 
struct PID spid; // PID Control Structure 
unsigned int rout; // PID Response (Output) 
unsigned int rin; // PID Feedback (Input) 
sbit data1=P1^0; 
sbit clk=P1^1; 
sbit plus=P2^0; 
sbit subs=P2^1; 
sbit stop=P2^2; 
sbit output=P3^4; 
sbit DQ=P3^3; 
unsigned char flag,flag_1=0; 
unsigned char high_time,low_time,count=0;//占空比调节参数 
unsigned char set_temper=35; 
unsigned char temper; 
unsigned char i; 
unsigned char j=0; 
unsigned int s; 
/*********************************************************** 
延时子程序,延时时间以12M晶振为准,延时时间为30us×time 
***********************************************************/ 
void delay(unsigned char time) 
{ 
unsigned char m,n; 
for(n=0;n＜time;n++) 
for(m=0;m＜2;m++){} 
} 
/*********************************************************** 
写一位数据子程序 
***********************************************************/ 
void write_bit(unsigned char bitval) 
{ 
EA=0; 
DQ=0; /*拉低DQ以开始一个写时序*/ 
if(bitval==1) 
{ 
  _nop_(); 
  DQ=1; /*如要写1，则将总线置高*/ 
} 
delay(5); /*延时90us供DA18B20采样*/ 
DQ=1; /*释放DQ总线*/ 
_nop_(); 
_nop_(); 
EA=1; 
} 
/*********************************************************** 
写一字节数据子程序 
***********************************************************/ 
void write_byte(unsigned char val) 
{ 
unsigned char i; 
unsigned char temp; 
EA=0; 
TR0=0; 
for(i=0;i＜8;i++) /*写一字节数据，一次写一位*/ 
{ 
  temp=val>>i; /*移位操作，将本次要写的位移到最低位*/ 
  temp=temp&1; 
  write_bit(temp); /*向总线写该位*/ 
} 
delay(7); /*延时120us后*/ 
// TR0=1; 
EA=1; 
} 
/*********************************************************** 
读一位数据子程序 
***********************************************************/ 
unsigned char read_bit() 
{ 
unsigned char i,value_bit; 
EA=0; 
DQ=0; /*拉低DQ，开始读时序*/ 
_nop_(); 
_nop_(); 
DQ=1; /*释放总线*/ 
for(i=0;i＜2;i++){} 
value_bit=DQ; 
EA=1; 
return(value_bit); 
} 
/*********************************************************** 
读一字节数据子程序 
***********************************************************/ 
unsigned char read_byte() 
{ 
unsigned char i,value=0; 
EA=0; 
for(i=0;i＜8;i++) 
{ 
  if(read_bit()) /*读一字节数据，一个时序中读一次，并作移位处理*/ 
  value|=0x01＜＜i; 
  delay(4); /*延时80us以完成此次都时序，之后再读下一数据*/ 
} 
EA=1; 
return(value); 
} 
/*********************************************************** 
复位子程序 
***********************************************************/ 
unsigned char reset() 
{ 
unsigned char presence; 
EA=0; 
DQ=0; /*拉低DQ总线开始复位*/ 
delay(30); /*保持低电平480us*/ 
DQ=1; /*释放总线*/ 
delay(3); 
presence=DQ; /*获取应答信号*/ 
delay(28); /*延时以完成整个时序*/ 
EA=1; 
return(presence); /*返回应答信号，有芯片应答返回0,无芯片则返回1*/ 
} 
/*********************************************************** 
获取温度子程序 
***********************************************************/ 
void get_temper() 
{ 
unsigned char i,j; 
do 
{ 
  i=reset(); /*复位*/ 
}while(i!=0); /*1为无反馈信号*/ 
i=0xcc; /*发送设备定位命令*/ 
write_byte(i); 
i=0x44; /*发送开始转换命令*/ 
write_byte(i); 
delay(180); /*延时*/ 
do 
{ 
  i=reset(); /*复位*/ 
}while(i!=0); 
i=0xcc; /*设备定位*/ 
write_byte(i); 
i=0xbe; /*读出缓冲区内容*/ 
write_byte(i); 
j=read_byte(); 
i=read_byte(); 
i=(i＜＜4)&0x7f; 
s=(unsigned int)(j&0x0f); 
s=(s*100)/16; 
j=j>>4; 
temper=i|j; /*获取的温度放在temper中*/ 
} 
/*==================================================================================================== 
Initialize PID Structure 
=====================================================================================================*/ 
void PIDInit (struct PID *pp) 
{ 
memset ( pp,0,sizeof(struct PID)); 
} 
/*==================================================================================================== 
PID计算部分 
=====================================================================================================*/ 
unsigned int PIDCalc( struct PID *pp, unsigned int NextPoint ) 
{ 
unsigned int dError,Error; 
Error = pp->SetPoint - NextPoint; // 偏差 
pp->SumError += Error; // 积分 
dError = pp->LastError - pp->PrevError; // 当前微分 
pp->PrevError = pp->LastError; 
pp->LastError = Error; 
return (pp->Proportion * Error // 比例项 
+ pp->Integral * pp->SumError // 积分项 
+ pp->Derivative * dError); // 微分项 
} 
/*********************************************************** 
温度比较处理子程序 
***********************************************************/ 
compare_temper() 
{ 
unsigned char i; 
if(set_temper>temper) 
{ 
  if(set_temper-temper>1) 
  { 
   high_time=100; 
   low_time=0; 
  } 
  else 
  { 
   for(i=0;i＜10;i++) 
   { 
    get_temper(); 
    rin = s; // Read Input 
    rout = PIDCalc ( &spid,rin ); // Perform PID Interation 
   } 
   if (high_time＜=100) 
   {
    high_time=(unsigned char)(rout/800); 
   }
   else 
   {
    high_time=100;
      }
   low_time= (100-high_time); 
  } 
} 
else if(set_temper＜=temper) 
{ 
  if(temper-set_temper>0) 
  { 
   high_time=0; 
   low_time=100; 
  } 
  else 
  { 
   for(i=0;i＜10;i++) 
   { 
    get_temper(); 
    rin = s; // Read Input 
    rout = PIDCalc ( &spid,rin ); // Perform PID Interation 
   } 
   if (high_time＜100) 
   {
    high_time=(unsigned char)(rout/10000); 
   }
   else 
   {
    high_time=0; 
   }
   low_time= (100-high_time); 
  } 
} 
// else 
// {} 
} 
/***************************************************** 
T0中断服务子程序，用于控制电平的翻转 ,40us*100=4ms周期 
******************************************************/ 
void serve_T0() interrupt 1 using 1 
{ 
if(++count＜=(high_time)) 
output=1; 
else if(count＜=100) 
{ 
  output=0; 
} 
else 
count=0; 
TH0=0x2f; 
TL0=0xe0; 
} 
/***************************************************** 
串行口中断服务程序，用于上位机通讯 
******************************************************/ 
void serve_sio() interrupt 4 using 2 
{ 
/* EA=0; 
RI=0; 
i=SBUF; 
if(i==2) 
{ 
while(RI==0){} 
RI=0; 
set_temper=SBUF; 
SBUF=0x02; 
while(TI==0){} 
TI=0; 
} 
else if(i==3) 
{ 
TI=0; 
SBUF=temper; 
while(TI==0){} 
TI=0; 
} 
EA=1; */ 
} 
void disp_1(unsigned char disp_num1[6]) 
{ 
unsigned char n,a,m; 
for(n=0;n＜6;n++) 
{ 
// k=disp_num1[n]; 
  for(a=0;a＜8;a++) 
  { 
   clk=0; 
   m=(disp_num1[n]&1); 
   disp_num1[n]=disp_num1[n]>>1; 
   if(m==1) 
   data1=1; 
   else 
   data1=0; 
   _nop_(); 
   clk=1; 
   _nop_(); 
  } 
} 
} 
/***************************************************** 
显示子程序 
功能：将占空比温度转化为单个字符，显示占空比和测得到的温度 
******************************************************/ 
void display() 
{ 
unsigned char code number[]={0xfc,0x60,0xda,0xf2,0x66,0xb6,0xbe,0xe0,0xfe,0xf6}; 
unsigned char disp_num[6]; 
unsigned int k,k1; 
k=high_time; 
k=k%1000; 
k1=k/100; 
if(k1==0) 
disp_num[0]=0; 
else 
disp_num[0]=0x60; 
k=k%100; 
disp_num[1]=number[k/10]; 
disp_num[2]=number[k%10]; 
k=temper; 
k=k%100; 
disp_num[3]=number[k/10]; 
disp_num[4]=number[k%10]+1; 
disp_num[5]=number[s/10]; 
disp_1(disp_num); 
} 
/*********************************************************** 
主程序 
***********************************************************/ 
main() 
{ 
unsigned char z; 
unsigned char a,b,flag_2=1,count1=0; 
unsigned char phil[]={2,0xce,0x6e,0x60,0x1c,2};; 
TMOD=0x21; 
TH0=0x2f; 
TL0=0x40; 
SCON=0x50; 
PCON=0x00; 
TH1=0xfd; 
TL1=0xfd; 
PS=1; 
EA=1; 
EX1=0; 
ET0=1; 
ES=1; 
TR0=1; 
TR1=1; 
high_time=50; 
low_time=50; 
PIDInit ( &spid ); // Initialize Structure 
spid.Proportion = 10; // Set PID Coefficients 
spid.Integral = 8; 
spid.Derivative =6; 
spid.SetPoint = 100; // Set PID Setpoint 
while(1) 
{ 
  if(plus==0) 
  { 
   EA=0; 
   for(a=0;a＜5;a++) 
    for(b=0;b＜102;b++){} 
   if(plus==0) 
   { 
    set_temper++; 
    flag=0; 
   } 
  } 
  else if(subs==0) 
  { 
   for(a=0;a＜5;a++) 
    for(b=0;a＜102;b++){} 
   if(subs==0) 
   { 
    set_temper--; 
    flag=0; 
   } 
  } 
  else if(stop==0) 
  { 
   for(a=0;a＜5;a++) 
    for(b=0;b＜102;b++){} 
   if(stop==0) 
   { 
    flag=0; 
    break; 
   } 
   EA=1; 
  } 
  get_temper(); 
  b=temper; 
  if(flag_2==1) 
  {
   a=b;
  } 
  if((abs(a-b))>5) 
  {
   temper=a;
  } 
  else 
  {  
   temper=b;
  } 
  a=temper; 
  flag_2=0; 
  if(++count1>30) 
  { 
   display(); 
   count1=0; 
  } 
  compare_temper(); 
} 
TR0=0; 
z=1; 
while(1) 
{ 
  EA=0; 
  if(stop==0) 
  { 
   for(a=0;a＜5;a++) 
    for(b=0;b＜102;b++){} 
   if(stop==0) 
   disp_1(phil); 
   // break; 
  } 
  EA=1; 
} 
}