- #include <stdio.h>
- #include<math.h>
- //定義PID 的結構體
- struct _pid
- {
- int pv; //integer that contains the process value 過程量
- int sp; //＊integer that contains the set point 設定值
- float integral; // 積分值 －－ 偏差累計值
- float pgain;
- float igain;
- float dgain;
- int deadband; //死區
- 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.
- 設定PID參數 －－－－ P,I,D,死區
- －－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－ */
- 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.
- 設定輸出初始值
- －－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－ */
- 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.
- pid_bumpless 實現無擾切換
- 當突然改變設定值時，或重新啟動后，將引起擾動輸出。這
- 個函數將能實現平順擾動， 在調用該函數之前需要先更新 PV值
- －－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－*/
- void pid_bumpless(struct _pid *pid)
- {
- pid->last_error = (pid->sp)-(pid->pv); //設定值與反饋值偏差
- }
- /*－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
- 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"
- 本函數使用位置式PID計算方式，并且采取了積分飽和限制運算
- PID計算
- －－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－*/
- float pid_calc(struct _pid *pid)
- {
- int err;
- float pterm, dterm, result, ferror;
- // 計算偏差
- err = (pid->sp) - (pid->pv);
- // 判斷是否大于死區
- if (abs(err) > pid->deadband)
- {
- ferror = (float) err; //do integer to float conversion only once 數據類型轉換
- // 比例項
- pterm = pid->pgain * ferror;
- if (pterm > 100 || pterm < -100)
- {
- pid->integral = 0.0;
- }
- else
- {
- // 積分項
- pid->integral += pid->igain * ferror;
- // 輸出為0－－100%
- // 如果計算結果大于100，則等于100
- if (pid->integral > 100.0)
- {
- pid->integral = 100.0;
- }
- // 如果計算結果小于0.0，則等于0
- else if (pid->integral < 0.0)
- {
- pid->integral = 0.0;
- }
- }
- // 微分項
- dterm = ((float)(err - pid->last_error)) * pid->dgain;
- result = pterm + pid->integral + dterm;
- }
- else
- {
- result = pid->integral; // 在死區范圍內，保持現有輸出
- }
- // 保存上次偏差
- pid->last_error = err;
- // 輸出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);
- // 初始化參數
- 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);
- // 設定PV,SP 值
- pid_init(&warm, process_point, set_point);
- // 初始化PID 參數值
- pid_tune(&warm, p_gain,i_gain,d_gain,dead_band);
- // 初始化PID 輸出值
- 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,wa
- rm.dgain);
- count++;
- }
- }
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