msp430单片机中增量式pid算法的C实现方法

　#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++; 

　　 

　　 } 

　　

　　}