/************  PID算法(C语言)  ************/　　#include 
     
      　　#include
      
       　　　　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++; 　　 } 　　}