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146 lines
5.4 KiB
Plaintext
146 lines
5.4 KiB
Plaintext
6 months ago
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<?xml version="1.0" encoding="utf-8"?>
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<TcPlcObject Version="1.1.0.1" ProductVersion="3.1.4024.12">
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<POU Name="fbPID" Id="{ba0371f9-f611-44ea-97d3-8d6e71d4762a}" SpecialFunc="None">
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<Declaration><![CDATA[FUNCTION_BLOCK fbPID
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VAR_INPUT
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Setpoint: REAL; (* Desired setpoint *)
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ProcessValue: REAL; (* Current process value *)
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Enable: BOOL; (* Enable/disable PID control *)
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END_VAR
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VAR_OUTPUT
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ControlOutput: REAL; (* Output of PID controller *)
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END_VAR
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VAR
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// -- PID parameters
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Kp: REAL := 0.0; (* Proportional gain *)
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Ki: REAL := 0.0; (* Integral gain *)
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Kd: REAL := 0.0; (* Derivative gain *)
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// -- Internal variables
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LastError: REAL := 0.0; (* Error at previous sample *)
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Integral: REAL := 0.0; (* Integral of error over time *)
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SampleTime: TIME := T#1S; (* Sampling time *)
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// -- Auto-tuning parameters
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AutoTuneStep: REAL := 0.1; (* Step size for auto-tuning *)
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SettlingTime: TIME := T#5S;(* Desired settling time for auto-tuning *)
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LastStepTime: TIME := T#0S;(* Time of last auto-tune step *)
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AutoTuning: BOOL := FALSE; (* Auto-tuning flag *)
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InitStep: BOOL := TRUE; (* Flag for initial step in auto-tuning *)
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END_VAR
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]]></Declaration>
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<Implementation>
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<ST><![CDATA[(* Function to perform auto-tuning *)
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FUNCTION AutoTunePID : BOOL
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VAR
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CurrentTime: TIME;
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Error: REAL;
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DeltaTime: TIME;
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BEGIN
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CurrentTime := TcSysTime(); (* Get current system time *)
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Error := ABS(ProcessValue - Setpoint);
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IF Error < 0.05 * Setpoint THEN (* Acceptable error threshold *)
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IF NOT InitStep THEN
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DeltaTime := CurrentTime - LastStepTime; (* Calculate time difference *)
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SampleTime := TIME_TO_REAL(DeltaTime) / 2; (* Calculate sample time *)
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Kp := 0.6 / (ProcessValue * AutoTuneStep); (* Calculate proportional gain *)
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Ki := 2 * Kp / (0.3 * TIME_TO_REAL(SettlingTime)); (* Calculate integral gain *)
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Kd := Kp * 0.125 * TIME_TO_REAL(SettlingTime); (* Calculate derivative gain *)
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AutoTuning := FALSE;
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AutoTunePID := TRUE;
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EXIT;
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END_IF;
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ELSE
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InitStep := FALSE;
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LastStepTime := CurrentTime;
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IF ProcessValue > Setpoint THEN
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ProcessValue := ProcessValue - AutoTuneStep * Setpoint; (* Decrease process value *)
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ELSE
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ProcessValue := ProcessValue + AutoTuneStep * Setpoint; (* Increase process value *)
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END_IF;
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END_IF;
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AutoTunePID := FALSE;
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END_FUNCTION;
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(* Function to perform PID control *)
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FUNCTION PIDControl : VOID
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VAR
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Error: REAL;
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Proportional: REAL;
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IntegralTerm: REAL;
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DerivativeTerm: REAL;
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BEGIN
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IF Enable THEN
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Error := Setpoint - ProcessValue;
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IF AutoTuning THEN
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IF AutoTunePID() THEN
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RETURN;
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END_IF;
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END_IF;
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Integral := Integral + (Error * SampleTime); (* Integral term calculation *)
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Integral := MAX(MIN(Integral, 1000), -1000); (* Anti-windup limit *)
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Proportional := Kp * Error; (* Proportional term *)
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IntegralTerm := Ki * Integral; (* Integral term *)
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DerivativeTerm := Kd * (Error - LastError) / SampleTime; (* Derivative term *)
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ControlOutput := Proportional + IntegralTerm + DerivativeTerm;
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LastError := Error; (* Update last error *)
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ELSE
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ControlOutput := 0.0; (* Disable control if not enabled *)
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Integral := 0.0; (* Reset integral term *)
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LastError := 0.0; (* Reset last error *)
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END_IF;
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END_FUNCTION;]]></ST>
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</Implementation>
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<Method Name="AutoTunePID" Id="{a72ed6ef-5938-4dfc-b7ba-21356dc9bded}">
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<Declaration><![CDATA[METHOD AutoTunePID : BOOL
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VAR_INPUT
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CurrentTime: TIME;
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Error: REAL;
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DeltaTime: TIME;
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END_VAR
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]]></Declaration>
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<Implementation>
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<ST><![CDATA[ CurrentTime := TcSysTime(); (* Get current system time *)
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Error := ABS(ProcessValue - Setpoint);
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IF Error < 0.05 * Setpoint THEN (* Acceptable error threshold *)
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IF NOT InitStep THEN
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DeltaTime := CurrentTime - LastStepTime; (* Calculate time difference *)
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SampleTime := TIME_TO_REAL(DeltaTime) / 2; (* Calculate sample time *)
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Kp := 0.6 / (ProcessValue * AutoTuneStep); (* Calculate proportional gain *)
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Ki := 2 * Kp / (0.3 * TIME_TO_REAL(SettlingTime)); (* Calculate integral gain *)
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Kd := Kp * 0.125 * TIME_TO_REAL(SettlingTime); (* Calculate derivative gain *)
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AutoTuning := FALSE;
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AutoTunePID := TRUE;
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EXIT;
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END_IF;
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ELSE
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InitStep := FALSE;
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LastStepTime := CurrentTime;
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IF ProcessValue > Setpoint THEN
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ProcessValue := ProcessValue - AutoTuneStep * Setpoint; (* Decrease process value *)
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ELSE
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ProcessValue := ProcessValue + AutoTuneStep * Setpoint; (* Increase process value *)
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END_IF;
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END_IF;
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AutoTunePID := FALSE;]]></ST>
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</Implementation>
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</Method>
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<LineIds Name="fbPID">
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<LineId Id="30" Count="65" />
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<LineId Id="9" Count="0" />
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</LineIds>
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<LineIds Name="fbPID.AutoTunePID">
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<LineId Id="9" Count="23" />
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<LineId Id="5" Count="0" />
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</LineIds>
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</POU>
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</TcPlcObject>
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