Windsor_MILLST605/605MILL/POUs/FB/fbPID.TcPOU

<?xml version="1.0" encoding="utf-8"?>
<TcPlcObject Version="1.1.0.1" ProductVersion="3.1.4024.12">
  <POU Name="fbPID" Id="{ba0371f9-f611-44ea-97d3-8d6e71d4762a}" SpecialFunc="None">
    <Declaration><![CDATA[FUNCTION_BLOCK fbPID
VAR_INPUT
	Setpoint: REAL;             (* Desired setpoint *)
    ProcessValue: REAL;         (* Current process value *)
    Enable: BOOL;               (* Enable/disable PID control *)
END_VAR
VAR_OUTPUT
	ControlOutput: REAL;       (* Output of PID controller *)
END_VAR
VAR
//	-- PID parameters
    Kp: REAL := 0.0;           (* Proportional gain *)
    Ki: REAL := 0.0;           (* Integral gain *)
    Kd: REAL := 0.0;           (* Derivative gain *)

//    -- Internal variables
    LastError: REAL := 0.0;    (* Error at previous sample *)
    Integral: REAL := 0.0;     (* Integral of error over time *)
    SampleTime: TIME := T#1S;  (* Sampling time *)

//    -- Auto-tuning parameters
    AutoTuneStep: REAL := 0.1; (* Step size for auto-tuning *)
    SettlingTime: TIME := T#5S;(* Desired settling time for auto-tuning *)
    LastStepTime: TIME := T#0S;(* Time of last auto-tune step *)
    AutoTuning: BOOL := FALSE; (* Auto-tuning flag *)
    InitStep: BOOL := TRUE;    (* Flag for initial step in auto-tuning *)
END_VAR
]]></Declaration>
    <Implementation>
      <ST><![CDATA[(* Function to perform auto-tuning *)
FUNCTION AutoTunePID : BOOL
VAR
    CurrentTime: TIME;
    Error: REAL;
    DeltaTime: TIME;
BEGIN
    CurrentTime := TcSysTime();  (* Get current system time *)
    Error := ABS(ProcessValue - Setpoint);

    IF Error < 0.05 * Setpoint THEN (* Acceptable error threshold *)
        IF NOT InitStep THEN
            DeltaTime := CurrentTime - LastStepTime; (* Calculate time difference *)
            SampleTime := TIME_TO_REAL(DeltaTime) / 2; (* Calculate sample time *)
            Kp := 0.6 / (ProcessValue * AutoTuneStep);     (* Calculate proportional gain *)
            Ki := 2 * Kp / (0.3 * TIME_TO_REAL(SettlingTime));           (* Calculate integral gain *)
            Kd := Kp * 0.125 * TIME_TO_REAL(SettlingTime);               (* Calculate derivative gain *)
            AutoTuning := FALSE;
            AutoTunePID := TRUE;
            EXIT;
        END_IF;
    ELSE
        InitStep := FALSE;
        LastStepTime := CurrentTime;
        IF ProcessValue > Setpoint THEN
            ProcessValue := ProcessValue - AutoTuneStep * Setpoint; (* Decrease process value *)
        ELSE
            ProcessValue := ProcessValue + AutoTuneStep * Setpoint; (* Increase process value *)
        END_IF;
    END_IF;

    AutoTunePID := FALSE;
END_FUNCTION;

(* Function to perform PID control *)
FUNCTION PIDControl : VOID
VAR
    Error: REAL;
    Proportional: REAL;
    IntegralTerm: REAL;
    DerivativeTerm: REAL;
BEGIN
    IF Enable THEN
        Error := Setpoint - ProcessValue;

        IF AutoTuning THEN
            IF AutoTunePID() THEN
                RETURN;
            END_IF;
        END_IF;

        Integral := Integral + (Error * SampleTime);  (* Integral term calculation *)
        Integral := MAX(MIN(Integral, 1000), -1000); (* Anti-windup limit *)

        Proportional := Kp * Error;                   (* Proportional term *)
        IntegralTerm := Ki * Integral;                 (* Integral term *)
        DerivativeTerm := Kd * (Error - LastError) / SampleTime; (* Derivative term *)

        ControlOutput := Proportional + IntegralTerm + DerivativeTerm;

        LastError := Error;                           (* Update last error *)
    ELSE
        ControlOutput := 0.0;                         (* Disable control if not enabled *)
        Integral := 0.0;                              (* Reset integral term *)
        LastError := 0.0;                             (* Reset last error *)
    END_IF;
END_FUNCTION;]]></ST>
    </Implementation>
    <Method Name="AutoTunePID" Id="{a72ed6ef-5938-4dfc-b7ba-21356dc9bded}">
      <Declaration><![CDATA[METHOD AutoTunePID : BOOL
VAR_INPUT
	CurrentTime: TIME;
    Error: REAL;
    DeltaTime: TIME;
END_VAR
]]></Declaration>
      <Implementation>
        <ST><![CDATA[    CurrentTime := TcSysTime();  (* Get current system time *)
    Error := ABS(ProcessValue - Setpoint);

    IF Error < 0.05 * Setpoint THEN (* Acceptable error threshold *)
        IF NOT InitStep THEN
            DeltaTime := CurrentTime - LastStepTime; (* Calculate time difference *)
            SampleTime := TIME_TO_REAL(DeltaTime) / 2; (* Calculate sample time *)
            Kp := 0.6 / (ProcessValue * AutoTuneStep);     (* Calculate proportional gain *)
            Ki := 2 * Kp / (0.3 * TIME_TO_REAL(SettlingTime));           (* Calculate integral gain *)
            Kd := Kp * 0.125 * TIME_TO_REAL(SettlingTime);               (* Calculate derivative gain *)
            AutoTuning := FALSE;
            AutoTunePID := TRUE;
            EXIT;
        END_IF;
    ELSE
        InitStep := FALSE;
        LastStepTime := CurrentTime;
        IF ProcessValue > Setpoint THEN
            ProcessValue := ProcessValue - AutoTuneStep * Setpoint; (* Decrease process value *)
        ELSE
            ProcessValue := ProcessValue + AutoTuneStep * Setpoint; (* Increase process value *)
        END_IF;
    END_IF;

    AutoTunePID := FALSE;]]></ST>
      </Implementation>
    </Method>
    <LineIds Name="fbPID">
      <LineId Id="30" Count="65" />
      <LineId Id="9" Count="0" />
    </LineIds>
    <LineIds Name="fbPID.AutoTunePID">
      <LineId Id="9" Count="23" />
      <LineId Id="5" Count="0" />
    </LineIds>
  </POU>
</TcPlcObject>