比例P控制：控制器的输出与输入误差成比例关系，系统输出存在稳态误差。积分I控制：控制器的输出与输入误差的积分成正比关系，积分项会随着时间的增加而加大，会推动控制器的输出增大使稳态误差进一步减小，直到等于零；所以比例+积分（PI）控制器，可以使系统在进入稳态后无稳态误差。微分D控制：控制器的输出与输入误差的微分成正比关系。比例项的作用仅是放大误差的幅值，而需要增加的是“微分项”，它能预测误差变化的趋势，比例+微分（PD）控制器能改善系统在调节过程中的动态特性。
PID控制器的参数整定方法有两类。其中一种是理论计算整定法，依据系统的数学模型，经过理论计算确定控制器参数。另一种是工程整定方法，依赖工程经验，直接在控制系统的试验中进行，方法简单、易于掌握。
C语言实现PID算法BC31 TC30 编译过，可运行。
#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++
}
}
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