PID算法（c 语言)（来自老外）

#include <stdio.h> 
#include<math.h>

//定义PID 的结构体 
struct _pid
{
  int pv;         // integer that contains the process value 过程量 
  int sp;         // integer that contains the set point   设定值 
  float integral; // 积分值 －－ 偏差累计值 
  float pgain;
  float igain;
  float dgain;
  int deadband;   //死区 
  int last_error;
};

struct _pid warm, *pid;
int process_point, set_point, dead_band;
float p_gain, i_gain, d_gain, integral_val, new_integ;

/* 
 pid_init --- This function initializes the 
 pointers  in  the  _pid  structure  to  the  process  variable 
 and the setpoint. *pv and *sp are integer pointers. 
 */

void pid_init( struct _pid *warm, int process_point, int set_point )
{
  struct _pid *pid;
  pid = warm;
  pid->pv = process_point;
  pid->sp = set_point;
}

/*pid_tune --- Sets the proportional gain (p_gain), integral gain (i_gain), 
 derivitive  gain  (d_gain),  and  the  dead  band  (dead_band) 
 of a pid control structure _pid.

 设定PID参数 －－－－ P,I,D,死区 
 */

void pid_tune( struct _pid *pid,
  float p_gain,
  float i_gain,
  float d_gain,
  int dead_band )
{
  pid->pgain = p_gain;
  pid->igain = i_gain;
  pid->dgain = d_gain;
  pid->deadband = dead_band;
  pid->integral = integral_val;
  pid->last_error = 0;
}

/*
 pid_setinteg --- Set a new value for the integral term of the pid equation. 
 This is useful for setting the initial output of the pid controller at start up. 

 设定输出初始值 
 */

void pid_setinteg( struct _pid *pid, float new_integ )
{
  pid->integral = new_integ;
  pid->last_error = 0;
}

/*
 
 pid_bumpless --- Bumpless transfer  algorithim. 
 When suddenly changing setpoints, or when restarting  the PID equation 
 after an extended pause, the derivative of the equation can cause a bump 
 in the controller output. This function will help smooth out  that bump. 
 The process value in *pv should be the updated just before this function is used. 

 pid_bumpless 实现无扰切换 
 当突然改变设定值时，或重新启动后，将引起扰动输出。这
 个函数将能实现平顺扰动， 在调用该函数之前需要先更新 PV值 
 */

void pid_bumpless( struct _pid *pid )
{
  pid->last_error = ( pid->sp ) - ( pid->pv );  //设定值与反馈值偏差 
}

/* 
 pid_calc  ---  Performs  PID  calculations  for  the  _pid structure * a. 
 This function uses the positional form of the pid 
 equation, and incorporates an integral windup prevention algorithim. 
 Rectangular  integration  is  used,  so  this  function  must 
 be repeated on a consistent time basis for accurate  control. 
 RETURN VALUE The new output value for the pid loop.  USAGE #include "control.h" 
 本函数使用位置式PID计算方式，并且采取了积分饱和限制运算 
 PID计算 
 */

float pid_calc( struct _pid *pid )
{
  int err;
  float pterm, dterm, result, ferror;
  
  // 计算偏差 
  err = ( pid->sp ) - ( pid->pv );
  
  // 判断是否大于死区 
  if ( abs( err ) > pid->deadband )
  {
    ferror = (float) err;   //do integer to float conversion only once 数据类型转换 
      
    // 比例项 
    pterm = pid->pgain * ferror;
    
    if ( pterm > 100 || pterm < -100 )
    {
      pid->integral = 0.0;
    }
    else
    {
      // 积分项 
      pid->integral += pid->igain * ferror;
      
      // 输出为0－－100% 
      // 如果计算结果大于100，则等于100 
      if ( pid->integral > 100.0 )
      {
        pid->integral = 100.0;
      }
      // 如果计算结果小于0.0，则等于0 
      else if ( pid->integral < 0.0 )
        pid->integral = 0.0;
      
    }
    
    // 微分项 
    dterm = ( (float) ( err - pid->last_error ) ) * pid->dgain;
    
    result = pterm + pid->integral + dterm;
  }
  else
    result = pid->integral; // 在死区范围内，保持现有输出 
      
  // 保存上次偏差 
  pid->last_error = err;
  
  // 输出PID值(0-100) 
  return ( result );
}

void main( void )
{
  float display_value;
  int count = 0;
  pid = &warm;
  
  // printf("Enter the values of Process point, Set point, P gain, I gain, D gain \n"); 
  // scanf("%d%d%f%f%f", &process_point, &set_point,&p_gain, &i_gain, &d_gain); 
  
  // 初始化参数 
  process_point = 30;
  set_point = 40;
  p_gain = (float) ( 5.2 );
  i_gain = (float) ( 0.77 );
  d_gain = (float) ( 0.18 );
  dead_band = 2;
  integral_val = (float) ( 0.01 );
  
  printf(    "The  values  of  Process  point,  Set  point,  P  gain, I gain, D gain \n" );
  printf( " %6d %6d %4f %4f %4f\n", process_point, set_point, p_gain, i_gain, d_gain );
  printf( "Enter the values of Process point\n" );
  while ( count <= 20 )
  {
    scanf( "%d", &process_point );
    
    // 设定PV,SP 值 
    pid_init( &warm, process_point, set_point );
    
    // 初始化PID 参数值 
    pid_tune( &warm, p_gain, i_gain, d_gain, dead_band );
    
    // 初始化PID 输出值 
    pid_setinteg( &warm, 0.0 );
    
    //pid_setinteg(&warm,30.0); 
    //Get input value for process point 
    pid_bumpless( &warm );
    
    // how to display output 
    display_value = pid_calc( &warm );
    
    printf( "%f\n", display_value );
    //printf("\n%f%f%f%f",warm.pv,warm.sp,warm.igain,warm.dgain); 
    
    count++;
  }
}