#include <stdio.h>
#include<math.h>
//定义PID 的结构体
struct _pid
{
int pv; // integer that contains the process value 过程量
int sp; // integer that contains the set point 设定值
float integral; // 积分值 －－ 偏差累计值
float pgain;
float igain;
float dgain;
int deadband; //死区
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 --- 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 --- 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.
设定PID参数 －－－－ P,I,D,死区
*/
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 --- 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.
设定输出初始值
*/
void pid_setinteg( struct _pid *pid, float new_integ )
{
pid->integral = new_integ;
pid->last_error = 0;
}
/*
pid_bumpless --- 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.
pid_bumpless 实现无扰切换
当突然改变设定值时，或重新启动后，将引起扰动输出。这
个函数将能实现平顺扰动， 在调用该函数之前需要先更新 PV值
*/
void pid_bumpless( struct _pid *pid )
{
pid->last_error = ( pid->sp ) - ( pid->pv ); //设定值与反馈值偏差
}
/*
pid_calc --- 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"
本函数使用位置式PID计算方式，并且采取了积分饱和限制运算
PID计算
*/
float pid_calc( struct _pid *pid )
{
int err;
float pterm, dterm, result, ferror;
// 计算偏差
err = ( pid->sp ) - ( pid->pv );
// 判断是否大于死区
if ( abs( err ) > pid->deadband )
{
ferror = (float) err; //do integer to float conversion only once 数据类型转换
// 比例项
pterm = pid->pgain * ferror;
if ( pterm > 100 || pterm < -100 )
{
pid->integral = 0.0;
}
else
{
// 积分项
pid->integral += pid->igain * ferror;
// 输出为0－－100%
// 如果计算结果大于100，则等于100
if ( pid->integral > 100.0 )
{
pid->integral = 100.0;
}
// 如果计算结果小于0.0，则等于0
else if ( pid->integral < 0.0 )
pid->integral = 0.0;
}
// 微分项
dterm = ( (float) ( err - pid->last_error ) ) * pid->dgain;
result = pterm + pid->integral + dterm;
}
else
result = pid->integral; // 在死区范围内，保持现有输出
// 保存上次偏差
pid->last_error = err;
// 输出PID值(0-100)
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);
// 初始化参数
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 );
// 设定PV,SP 值
pid_init( &warm, process_point, set_point );
// 初始化PID 参数值
pid_tune( &warm, p_gain, i_gain, d_gain, dead_band );
// 初始化PID 输出值
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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