#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++;  	} }