PID编程的实例！

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++

　 }

}

有时有必要保存Linux进程的 进程标识号 （PID）。在本教程中，我们将介绍一种使用.pid文件 存储PID的常用方法 ，以及一个使用方法的示例。

很多时候，应用程序会将PID写入文件以便于访问，特别是守护进程。它只是 一个仅包含进程的PID文本 文件。没有特定的规则创建或使用。这仅仅是一个简单有用的约定。

下面从创建.pid文件的简单例子开始介绍.pid文件

我们可以在脚本中创建.pid文件的一种方法是将$$的输出传递到文件中：

$$是一个Linux变量，它返回调用它的进程的PID。在这种情况下，它是shell的PID。

写个脚本并且运行起来

执行脚本

在另一个窗口执行ps命令查看进程pid

使用.pid文件kill掉该进程的命令

再次ps则不会出现刚刚的进程

pgrep命令可以从.pid文件得到pid

欢迎访问 我的博客

控制一个加热器的恒温100度，当开始加热时，离目标温度相差比较远，这时我们通常会加大加热，使温度快速上升，当温度超过100度时，我们则关闭输出，通常我们会使用这样一个函数：

e(t) = SP – y(t)

u(t) = e(t)*P

SP——设定值

e(t)——误差值

y(t)——反馈值

u(t)——输出值

P——比例系数

滞后性不是很大的控制对象使用比例控制方式就可以满足控制要求，但很多被控对象中因为有滞后性。

也就是如果设定温度是100度，当采用比例方式控制时，如果P选择比较大，则会出现当温度达到100度输出为0后，温度仍然会止不住的向上爬升，比方说升至130度，当温度超过100度太多后又开始回落，尽管这时输出开始出力加热，但温度仍然会向下跌落一定的温度才会止跌回升，比方说降至170度，最后整个系统会稳定在一定的范围内进行振荡。

扩展资料：

能够检测极低浓度挥发性有机化合物和其它有毒气体的仪器。尤其是对VOC的灵敏检测使其在应急事故检测中具有无可替代的作用，VOC是许多气体事故中的有害物质，对它的有效监测对于防灾减灾具有重要作用。

PID使用了一个紫外灯（UV）光源将有机物打成可被检测器检测到的正负离子（离子化）。检测器测量离子化了的气体的电荷并将其转化为电流信号，电流被放大并显示出“PPM”浓度值。在被检测后，离子重新复合成为原来的气体和蒸气。

PID是一种非破坏性检测器，它不会“燃烧”或永久性改变待测气体，这样一来，经过PID检测的气体仍可被收集做进一步的测定。

参考资料来源：百度百科--PID气体探测器

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