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Error cases

A robust system must anticipate and handle various error scenarios. We have tried to identify potential issues, such as overheating, ignition failure, and sensor malfunctions. For each error case, it outlines the trigger conditions, the sensors involved, and the actions taken to mitigate risks and ensure safety.

Error Case Trigger Condition Sensor(s) Outcome
Overheating case_temp > MAX_TEMP_THRESHOLD Case Temp Shut off fuel pump. Keep fan running to cool combustion chamber. Transition to Error state.
Failure to Ignite flame_sensor == FALSE or case_temp < IGNITION_TEMP_THRESHOLD after timeout Flame Sensor, Case Temp Stop pump to prevent flooding. Keep fan running to clear unburned fuel. Transition to Error state.
Flame Extinguished flame_sensor == FALSE or case_temp < FLAME_OUT_TEMP Flame Sensor, Case Temp Shut off fuel pump. Transition to Cooldown state to clear residual heat.
Overcooling case_temp < MIN_TEMP_THRESHOLD Case Temp Shut off pump and glow plug. Transition to Idle state to prevent unnecessary operation.
Ambient Overheat ambient_temp > AMBIENT_MAX_TEMP_THRESHOLD Ambient Temp Shut down the system (pump, glow plug, fan). Transition to Error state to signal overheating.
Fuel Pump Malfunction flame_sensor == FALSE or case temp doesn't rise Flame Sensor, Case Temp Stop all components (fuel pump, fan, glow plug). Transition to Error state.
Fan Failure No temp changes or flagged error Case Temp Transition to Error state. Attempt to restart the fan (if possible). Shut down other components if fan cannot be restarted.
Glow Plug Failure case_temp doesn't rise during Glow phase Case Temp Transition to Error state. Prompt a restart or alert user for maintenance.
Sensor Malfunction Invalid or static values (sensor_change_rate < MIN_RATE) Any Transition to Error state. Attempt sensor recalibration or notify user of faulty sensor.
Blocked Air Intake/Exhaust temp_change_rate > MAX_RATE or inlet_temp drops unexpectedly Case Temp, Inlet Temp Shut off fuel pump and glow plug. Keep fan running to clear combustion chamber. Transition to Error state.
Low Ambient Temperature ambient_temp < AMBIENT_MIN_TEMP_THRESHOLD Ambient Temp Notify user to address low temperature conditions. Transition to Idle state to avoid inefficient operation or damage.

1. Overheating

  • Cause: Combustion chamber temperature exceeds safe operating limits.
  • Sensor: Case Temperature Sensor
  • Variable/Trigger: case_temp > MAX_TEMP_THRESHOLD
    • MAX_TEMP_THRESHOLD could be a value like 250°C or based on manufacturer specs.

2. Failure to Ignite

  • Cause: The flame is not established within the expected timeframe during the ignition phase.
  • Sensor: Flame Sensor (optional), Case Temperature Sensor
  • Variable/Trigger:
    • flame_sensor == FALSE after a specific time (ignition_timeout).
    • case_temp < IGNITION_TEMP_THRESHOLD after ignition_timeout.

3. Flame Extinguished

  • Cause: Flame goes out unexpectedly during the Fire state.
  • Sensor: Flame Sensor (optional), Case Temperature Sensor
  • Variable/Trigger:
    • flame_sensor == FALSE during Fire state.
    • case_temp drops rapidly or below a predefined value (FLAME_OUT_TEMP).

4. Overcooling

  • Cause: Case temperature drops too low, possibly due to excessive airflow or incorrect operation.
  • Sensor: Case Temperature Sensor
  • Variable/Trigger: case_temp < MIN_TEMP_THRESHOLD

5. Ambient Overheat

  • Cause: The ambient temperature exceeds safe limits.
  • Sensor: Ambient Temperature Sensor
  • Variable/Trigger: ambient_temp > AMBIENT_MAX_TEMP_THRESHOLD

6. Fuel Pump Malfunction

  • Cause: Fuel pump fails to deliver fuel as expected.
  • Sensor: Flame Sensor, Case Temperature Sensor
  • Variable/Trigger:
    • flame_sensor == FALSE despite pump being active.
    • case_temp does not rise as expected during Fire.

7. Fan Failure

  • Cause: Fan does not operate or airflow is insufficient for combustion or cooling.
  • Sensor: None directly; inferred from system behavior.
  • Variable/Trigger:
    • No change in case_temp during Glow or Cooldown.
    • Error flag from the fan motor (if equipped).

8. Glow Plug Failure

  • Cause: Glow plug fails to heat the combustion chamber.
  • Sensor: Case Temperature Sensor
  • Variable/Trigger: case_temp does not rise during Glow phase.

9. Sensor Malfunction

  • Cause: Sensor reports invalid values or stops responding.
  • Sensor: Any
  • Variable/Trigger:
    • Out-of-range or invalid readings, e.g., case_temp == NULL or inlet_temp < 0°C.
    • Sensor readings are static when they should be dynamic (sensor_change_rate < MIN_RATE).

10. Blocked Air Intake or Exhaust

  • Cause: Airflow is restricted, causing incomplete combustion or overheating.
  • Sensor: Case Temperature Sensor, Inlet Temperature Sensor
  • Variable/Trigger:
    • case_temp rises abnormally fast (temp_change_rate > MAX_RATE).
    • inlet_temp drops despite fan activity.

11. Low Ambient Temperature

  • Cause: Ambient temperature too low for normal operation.
  • Sensor: Ambient Temperature Sensor
  • Variable/Trigger: ambient_temp < AMBIENT_MIN_TEMP_THRESHOLD

Error state Handling

Building upon the identified error cases, we discusses how the system transitions into and recovers from the Error state. We showcase user notifications, fail-safe measures, and system restarts for recoverable errors. The focus is on maintaining safety.

  • Error States:

    • Most errors transition the system to an Error state where the system components are either stopped or placed in a safe configuration. In many cases, the fan continues running to clear heat or fumes.

    • User Notifications:

    • Some errors (e.g., sensor malfunction, low ambient temperature) might require a user intervention or maintenance alert.

    • System Restarts:

    • For recoverable errors (e.g., blocked air intake or flame extinguished), the system can attempt a restart after clearing conditions.

    • Fail-Safe Measures:

    • The system prioritizes safety, ensuring no unburned fuel is left in the chamber, avoiding damage from overheating, and preventing unsafe operation under suboptimal conditions