/************  PID算法(C语言)  ************/#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 pointpid_bumpless(&warm);// how to display outputdisplay_value = pid_calc(&warm); printf("%f\n", display_value); //printf("\n%f%f%f%f",warm.pv,warm.sp,warm.igain,warm.dgain); count++; } }