pid2.c

PID微分,积分算法程序,编译已通过,可以直接使用!

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

struct _pid 
{
	int pv; /*integer that contains the process value*/
	int sp; /*integer that contains the set point*/
	float integral;
	float pgain;
	float igain;
	float dgain;
	int deadband;
	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. 
------------------------------------------------------------------------*/ 

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. 
------------------------------------------------------------------------*/ 
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. 
------------------------------------------------------------------------*/ 
void pid_bumpless(struct _pid *pid) 
{ 
 	pid->last_error = (pid->sp)-(pid->pv);  
} 

/*------------------------------------------------------------------------ 
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"*/ 


float pid_calc(struct _pid *pid)
{ 
	int err;
	float pterm, dterm, result, ferror; 
 
 	err = (pid->sp) - (pid->pv); 
 	if (abs(err) > pid->deadband) 
 	{ 
 		ferror = (float) err; /*do integer to float conversion only once*/ 
 		pterm = pid->pgain * ferror; 
 		if (pterm > 100 || pterm < -100)
 		{
 			pid->integral = 0.0; 
 		}
 		else 
 		{ 
 			pid->integral += pid->igain * ferror; 
 			if (pid->integral > 100.0) 
 			{
 				pid->integral = 100.0; 
 			}
 			else if (pid->integral < 0.0)
 			{ 
 				pid->integral = 0.0;
 			} 
 		} 
 		dterm = ((float)(err - pid->last_error)) * pid->dgain; 
 		result = pterm + pid->integral + dterm; 
 	} 
 	else
 	{ 
 		result = pid->integral; 
 	}
 	
 	pid->last_error = err; 
 	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); */

 	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);

 		pid_init(&warm, process_point, set_point);
 		pid_tune(&warm, p_gain,i_gain,d_gain,dead_band);
 		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++; 
 	} 
}