Simulated Faults

TeamCAMS simulates equipment malfunctions that can affect the operation of the cabin and threaten the stability of the system. These malfunctions, referred to as faults, are typically triggered by the experimental script at predefined times and require operators to diagnose and manage them using the information available through the Operator Interface.

To simplify diagnosis and experimental control, only one fault can be active at a time. Faults affect the behavior of valves, sensors, or devices, causing changes in cabin parameters such as oxygen concentration, carbon dioxide levels, pressure, temperature, or humidity. Operators must identify the underlying problem by monitoring system indicators, parameter trends, and device readings.

TeamCAMS supports five main categories of faults:

• Valve Blockage – A valve becomes partially blocked, reducing the flow of gases through the system.
• Valve Leak – A valve allows gas to escape, causing losses and inefficient operation.
• Valve Stuck – A valve remains permanently open or closed and no longer responds correctly to control commands.
• Sensor Failure – A sensor provides incorrect readings or stops functioning.
• Device Inefficiency – A subsystem continues to operate but with reduced effectiveness compared to normal conditions.

Examples include oxygen valve leaks, oxygen valves stuck open, inefficient CO₂ scrubbers, and partially blocked mixer valves. Each fault produces a characteristic set of symptoms that operators can use to determine the most likely cause of the problem.

For every fault type, TeamCAMS provides a corresponding repair procedure. In many cases operators must first stabilize the system by adjusting device settings before requesting a repair.

For example:

• An oxygen leak may require increasing oxygen flow while waiting for repairs.
• An inefficient scrubber may require increasing scrubber strength.
• A blocked mixer may require increasing both oxygen and nitrogen flow rates until maintenance is completed.

Repairs are requested through the Operator Interface and take a predefined amount of time to complete. Once the repair is finished, the faulty component returns to normal operation.

Experimental scripts may also automatically remove faults if participants are unable to resolve them within the expected time period, ensuring that the experiment can continue according to the planned scenario.

TeamCAMS implements several types of fault which can (negatively) affect the operation of the CAMS system. Faults can be activated during an experiment by adding an error element in the script. In the following you can find a list of the implemented faults.

Identifier: ox_valve_block

Description: the main oxygen valve is obstructed and only a fraction of the oxygen reaches the mixer and the cabin;

Diagnosis:

• the concentration of oxygen in the cabin decreases;
• the decrease rate of the oxygen in the tank is equal to the oxygen flow indicated by the meter;
• the flow of oxygen after the valve (as read on the corresponding meter) is lower than the target level (50% of the target level corresponding to the current strength).

Corrective actions:

• Set oxygen feed flow to high and retain automatic mode of control;
• Arrange for repair to be done.

Identifier: ox_stuck_open

Description: when the main oxygen valve opens it cannot be closed anymore;

Diagnosis:

• the system overview indicates that the main valve is permanently open (green lamp), even when flow is manually interrupted (using the command panel);
• the concentration of oxygen in the cabin increases ;
• the flow meter indicates a permanent flow;
• pressure inside the cabin increases, reaching the upper end of the target range (venting prevents an increase above the target range).

Corrective actions:

• Turn on and off oxygen feed flow until level is back to normal range.
• Arrange for repair to be done.

Identifiers: ox_sensor_upper, ox_sensor_lower, ox_sensor

Description: the sensor operates incorrectly and ignores either the upper threshold, the lower one or both thresholds;

Diagnosis:

• the oxygen value increases above the target level (ox_sensor_upper, ox_sensor) OR decreases below the target level (ox_sensor_lower, ox_sensor)
• ox_sensor_lower, ox_sensor: oxygen is not feed into the cabin anymore, flow meter reads zero
• ox_sensor_upper, ox_sensor: oxygen is continuously feed into the cabin;
• the value of the flow meter equals the target value for the selected strength;

Corrective actions:

• Turn on and off the oxygen feed flow until level is back to normal range.
• Arrange for repair to be done.
• Manual control of the oxygen feed flow until fault is eradicated.

Identifier: ni_valve_leak

Description: the main nitrogen valve leaks some gas ;

Diagnosis:

• pressure in the cabin decreases;
• the decrease rate of the nitrogen in the tank is higher than the nitrogen flow indicated by the meter;
• the flow of nitrogen after the valve (as read on the corresponding meter) is lower than the target level (corresponding to the current strength).

Corrective actions:

• Set nitrogen feed flow to high and retain automatic mode of control;
• Arrange for repair to be done.

Identifier: ni_valve_block

Description: the main nitrogen valve is obstructed and only a fraction of the nitrogen reaches the mixer and the cabin;

Diagnosis:

• pressure in the cabin decreases;
• the decrease rate of the nitrogen in the tank is higher than the nitrogen flow indicated by the meter;
• the flow of nitrogen after the valve (as read on the corresponding meter) is lower than the target level (50% of the target level corresponding to the current strength).

Corrective actions:

• Set nitrogen feed flow to high and retain automatic mode of control;
• Arrange for repair to be done.

Identifier: ni_stuck_open

Description: when the main nitrogen valve opens it cannot be closed anymore;

Diagnosis:

• the system overview indicates that the main valve is permanently open (green lamp), even when flow is manually interrupted (using the command panel);
• the flow meter indicates a permanent flow;
• pressure inside the cabin increases, reaching the upper end of the target range (venting prevents an increase above the target range).

Corrective actions:

• Turn on and off the nitrogen feed flow until level is back to normal range.
• Arrange for repair to be done.

Identifiers: ni_sensor_upper, ni_sensor_lower, ni_sensor

Description: the sensor operates incorrectly and ignores either the upper threshold, the lower one or both thresholds;

Diagnosis:

• the pressure inside the cabin increases above the target level (ni_sensor_upper, ni_sensor) OR decreases below the target level (ni_sensor_lower, ni_sensor)
• ni_sensor_lower, ni_sensor: nitrogen is not feed into the cabin anymore, flow meter reads zero;
• ni_sensor_upper, ni_sensor: nitrogen is continuously feed into the cabin;
• the value of the flow meter equals the target value for the selected strength;

Corrective actions:

• Turn on and off the nitrogen feed flow until level is back to normal range.
• Arrange for repair to be done.
• Manual control of the nitrogen feed flow until fault is eradicated.

Identifier: mixer_block

Description: the mixer valve is blocked and only a fraction of the gas goes to the cabin.

Diagnosis:

• the pressure in the cabin decreases;
• the concentration of oxygen in the cabin decreases;
• the decrease rate of the oxygen in the tank is equal to the oxygen flow indicated by the meter;
• the decrease rate of the nitrogen in the tank is equal to the nitrogen flow indicated by the meter;
• the flow of oxygen after the valve (as read on the corresponding meter) is lower than the target level (40% of the target level corresponding to the current strength).
• the flow of nitrogen after the valve (as read on the corresponding meter) is lower than the target level (50% of the target level corresponding to the current strength).

Corrective actions:

• Set oxygen feed flow to high and retain automatic mode of control;
• Set nitrogen feed flow to high and retain automatic mode of control;
• Arrange for repair to be done.

Identifiers: dehum_sensor, dehum_sensor_lower, dehum_sensor_upper, heat_sensor, heat_sensor_lower, heat_sensor_upper, cool_sensor, cool_sensor_lower, cool_sensor_upper, scrub_sensor, scrub_sensor_lower, scrub_sensor_upper, vent_sensor, vent_sensor_lower, vent_sensor_upper

Description: the sensor operates incorrectly and ignores either the upper threshold, the lower one or both thresholds;

Diagnosis:

• the specific parameter inside the cabin increases above the upper target level or drops below the lower target level;
• the specific device never turns on, or never turns off.

Corrective actions:

• Control the device manually until level is back to normal range.
• Arrange for repair to be done.

Identifiers: dehum_stuck_on, heat_stuck_on, cool_stuck_on, scrub_stuck_on, vent_stuck_on

Description: when the device is turned on it cannot be switched off anymore;

Diagnosis:

• the specific parameter inside the cabin increases or decreases, leading to values outside the target or the normal range.

Corrective actions:

• Manually decrease the device strength to the lowest setting until the level is back to normal range. If the heater is stuck on, turn the cooler on and increase its strength to compensate for the heating factor. If the cooler is stuck on, turn the heater on and increase its strength to compensate for the cooling factor. If the vent or the scrubber are stuck on, regulate manually pressure and oxygen.
• Arrange for repair to be done.

Identifiers: dehum_ineff, heat_ineff, cool_ineff, scrub_ineff, vent_ineff

Description: the device operates with lower performance;

Diagnosis:

• the specific parameter inside the cabin increases or decreases slower than normal, leading to values outside the target or the normal range.

Corrective actions:

• Manually increase the device strength until level is back to normal range.
• Arrange for repair to be done.