PID Cascade Simulator - Pasteurizer

Browser-based interactive simulator demonstrating cascade PID control advantages over single-loop control for pasteurization processes.

Live Demo: https://arthurkax.github.io/pid-cascade/

How to Use

Simply open the simulator in your browser - no installation required. The simulation starts automatically.

Control Modes

Manual Mode

1. Click Manual button
2. Use Valve Position slider (0-100%) or click valve in diagram
3. Observe temperature changes on HMI and charts

Auto Mode - 1 PID (Single Loop)

1. Click 1 PID button
2. Set SP (Setpoint) temperature (default: 72°C)
3. Adjust PID parameters to tune response
4. Watch the PID maintain setpoint by controlling the valve

Auto Mode - Cascade PID

1. Click Cascade PID button
2. The system uses two nested PID loops:
   • Outer Loop (Master): Controls milk temperature by setting steam pressure
   • Inner Loop (Slave): Controls steam pressure for faster disturbance rejection
3. Compare response with Single Loop mode when applying disturbances

Automated Test Sequence

Click Run Test to start a standardized evaluation of your PID tuning.

Test Phases

1. Warmup (max 360s)

   • All temperatures reset to 20°C (room temperature)
   • Waits for PV to reach SP (Setpoint)
   • After first touch, waits 15s for stabilization
   • IAE scoring starts ONLY after PV first reaches SP
   • This tests startup transient and overshoot

2. Cold Product (5°C) (max 360s)

   • Inlet temperature drops to 5°C
   • Tests disturbance rejection capability
   • Waits for inlet to reach 5°C ±0.5°C
   • Then waits 15s with |PV-SP| < 1°C for stabilization

3. Stabilization (max 180s)

   • Maintains at 5°C inlet temperature
   • Tests steady-state performance
   • 15s stabilization with |PV-SP| < 1°C required

4. Water (15°C) (max 300s)

   • Inlet temperature rises to 15°C
   • Tests response to positive temperature step
   • Waits for inlet to reach 15°C ±0.5°C
   • Then waits 15s with |PV-SP| < 1°C for stabilization

5. Boiler Failure (max 90s)

   • Simulates gradual steam pressure loss
   • Boiler pressure drops to 0.5 BAR
   • Maintains for 15s at 0.5 BAR
   • Tests robustness to equipment failure

Test Speed

The test runs at accelerated simulation speeds:

• Fast (5x): Default speed for efficient testing
• Turbo (10x): For quicker results
• Ludicrous (20x): For rapid iteration

You can adjust speed during test using the speed selector.

Scoring

• IAE (Integral Absolute Error): Accumulated absolute error
• Scoring starts ONLY after temperature first touches setpoint during warmup
• Errors within ±1.0°C don't increase score (deadband)
• Lower score = better control performance
• Score reflects: startup transient, overshoot, disturbance rejection, steady-state error

Leaderboard

After completing the test:

1. Score Modal shows your final IAE score, mode (Cascade/Single), and duration
2. Enter your name (max 20 characters)
3. Click Save Score to submit to Firebase leaderboard
4. View leaderboard to compare your tuning with others
5. Leaderboard shows: rank, name, score, mode, and date

Interactive Features

• Chart Tooltip: Hold ALT over chart to see all values at a specific time
• Variable Selection: Toggle variables on/off using color-matched buttons
• Technical Hints: Hold ALT while hovering over any control parameter (Kp, Ti, Td, etc.) to see its technical explanation
• Direct Input: Click sensors or valves in SVG diagram to interact directly

Simulation Controls

Speed Control

• Pause (0x): Freezes simulation
• Normal (1x): Standard speed
• Quick (2x) to Ludicrous (20x): Faster speeds for long-term testing

Disturbances

Test control system's robustness:

• Boiler Failure: Gradual steam pressure drop from 3 BAR to 0 BAR over 30 seconds
• Valve Wear (Deadband): Adds mechanical deadband (0-5%) where small valve commands are ignored
• Pressure Noise: Random pressure fluctuations (0-1 BAR) simulating other plant loads

Reset

• Reset Scene: Resets physics and time, keeps your PID tuning parameters

Control Panel

PID Parameters

Master PID (Temperature Control):

• Kp: Proportional gain (0.1-10)
• Ti (s): Integral time (0.1-1000s)
• Td (s): Derivative time (0-100s)
• Deadband (°C): Range around SP where controller freezes output
• SP (°C): Temperature setpoint (60-85°C)

Slave PID (Steam Control):

• Kp: Proportional gain (0.1-20)
• Ti (s): Integral time (0.1-500s)
• Td (s): Derivative time (0-50s)

License

MIT License - see LICENSE file.

Author

Created by ArthurkaX for PLC engineers and automation specialists.