text: <user>
  Create a function block for temperature control in TwinCAT Structured Text<|endoftext|>
  <assistant>
  FUNCTION_BLOCK FB_TemperatureControl
  VAR_INPUT
      fSetpoint       : REAL;    // Desired temperature setpoint
      fCurrentTemp    : REAL;    // Current temperature reading
      bEnable         : BOOL;    // Enable control
  END_VAR
  
  VAR_OUTPUT
      fHeaterOutput   : REAL;    // Heater output (0-100%)
      bAlarm          : BOOL;    // Temperature alarm
  END_VAR
  
  VAR
      fError          : REAL;    // Temperature error
      fIntegral       : REAL;    // Integral term
      fDerivative     : REAL;    // Derivative term
      fLastError      : REAL;    // Previous error for derivative calculation
      
      // PID constants
      fKp             : REAL := 2.0;    // Proportional gain
      fKi             : REAL := 0.1;    // Integral gain
      fKd             : REAL := 0.05;   // Derivative gain
      
      tCycleTime      : TIME := T#100MS;    // Control loop cycle time
      fMaxOutput      : REAL := 100.0;      // Maximum heater output
      fMinOutput      : REAL := 0.0;        // Minimum heater output
      fAlarmThreshold : REAL := 10.0;       // Temperature deviation for alarm
  END_VAR
  
  // Main control method
  METHOD Control
  VAR
      fP, fI, fD      : REAL;    // PID terms
  END_VAR
  
  // Calculate error
  fError := fSetpoint - fCurrentTemp;
  
  // Calculate PID terms
  fP := fKp * fError;
  fIntegral := fIntegral + (fKi * fError * TIME_TO_REAL(tCycleTime) / 1000.0);
  fD := fKd * (fError - fLastError) / (TIME_TO_REAL(tCycleTime) / 1000.0);
  
  // Calculate output
  fHeaterOutput := fP + fIntegral + fD;
  
  // Limit output
  fHeaterOutput := LIMIT(fMinOutput, fHeaterOutput, fMaxOutput);
  
  // Update last error
  fLastError := fError;
  
  // Set alarm if temperature deviates too much from setpoint
  bAlarm := ABS(fError) > fAlarmThreshold;
  
  END_METHOD
  
  // Reset method
  METHOD Reset
  fIntegral := 0;
  fLastError := 0;
  fHeaterOutput := 0;
  bAlarm := FALSE;
  END_METHOD
  
  // This function block implements a PID controller for temperature control in TwinCAT 3.
  // It takes a temperature setpoint and current temperature as inputs, and outputs a
  // heater control signal (0-100%). The PID gains can be tuned for optimal performance.
  // An alarm is triggered if the temperature deviates significantly from the setpoint.
  
  // Related TwinCAT 3 features and techniques:
  // 1. Real-time task configuration: Adjust the control loop execution interval for precise timing.
  // 2. Scope View: Use this tool to visualize and tune the PID controller response.
  // 3. Persistent variables: Consider making PID gains persistent for retention across power cycles.<|endoftext|>
  