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分类: C/C++

2014-01-03 17:09:58

PID算法(c 语言)(来自老外) 
(2010-02-17 00:18:24) 
转载 
#include  
#include 
//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 DESCRIPTION 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 DESCRIPTION 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 DESCRIPTION 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 DESCRIPTION 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  DESCRIPTION  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,wa
rm.dgain);


count++; 

}


老外的是位置式PID,我在网上找了增量式PID公式.如下:


△u=Kp*(e0-e1) + Ki*e0 + Kd*(e0 - 2*e1 + e2);
u += △u


e0为本次偏差; e1是上次偏差; e2是上上次偏差。u为本次输出。


 
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