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;]]> Setpoint THEN ProcessValue := ProcessValue - AutoTuneStep * Setpoint; (* Decrease process value *) ELSE ProcessValue := ProcessValue + AutoTuneStep * Setpoint; (* Increase process value *) END_IF; END_IF; AutoTunePID := FALSE;]]>