Aircraft Brake Control System Undetected Sensor Failure
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Solution Overview
Problem
Aircraft braking systems fail to maintain antiskid protection when pressure sensors fail undetected, as conventional systems cannot release braking pressure to zero, leading to potential wheel locking during skid conditions.
Innovation Solution
A brake control system that includes a brake control unit (BCU) with processors and memory, capable of implementing logic to detect pressure sensor failures and switch to open-loop servo valve current control, allowing for antiskid protection by outputting negative pressure commands to prevent wheel locking, even if the pressure sensor fails to a constant value within the normal range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional antiskid control is used with pressure sensors, then normal braking control is achieved, but the system cannot detect sensor failures and release pressure to zero when sensors fail undetected
Solution Approach 1:
The system performs preliminary detection of pressure sensor failures by monitoring for constant readings within the deadband range before skid conditions occur. When a failure is detected, the system proactively switches to open-loop control mode, preventing the situation where undetected failures would compromise antiskid protection.
Solution Approach 2:
The system uses feedback from pressure sensor readings to detect failures. By monitoring whether pressure readings remain constant within the deadband range, the system can identify sensor failures and respond by switching control modes, thereby maintaining reliability despite sensor issues.
2Ease of operation
If pressure sensor fails to constant value below deadband, then sensor reading remains in normal range, but conventional system cannot release braking pressure to zero
Solution Approach 1:
The system introduces an intermediary detection mechanism that monitors pressure sensor readings for failure patterns (constant values within deadband). This intermediary layer allows the system to recognize sensor failures even when readings appear normal, enabling appropriate control mode switching to maintain pressure release capability.
Solution Approach 2:
The system changes the control approach by switching from closed-loop pressure control to open-loop control when sensor failures are detected. This parameter change in control mode allows the system to release pressure to zero despite the faulty sensor readings, overcoming the limitation of conventional systems.
3Manufacturing precision
If closed-loop pressure control is used, then precise pressure control is achieved, but system fails when sensor readings are undetected and constant below deadband
Solution Approach 1:
The system dynamically switches between closed-loop and open-loop control modes based on sensor health status. When pressure sensor failures are detected, the system transitions from precise closed-loop control to open-loop control, maintaining reliability while adapting to the degraded sensor condition.
Solution Approach 2:
The system prepares for potential sensor failures by having open-loop control ready as a backup. When sensor failures occur, the pre-prepared open-loop control mode can immediately take over, cushioning against the harmful effects of undetected sensor failures and maintaining system reliability.
Data Source
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AI summary
A method for controlling brakes is provided. The method comprises detecting an imminent skid by an anti-skid controller/deceleration controller (ASK/DK) (112; 312). The ASK/DK (112; 312) outputs at least one of a negative desired pressure command (124) to a pressure control unit (PK) (116) in response to detecting the imminent skid and causes a current command output (126) from the PK (116) to be reduced to release braking pressure if the negative desired pressure command (124) minus a measured feedback pressure (132) is greater than a deadband of the PK (116) or outputs a negative desired force command (322) to a force control unit (ForK) (316) in response to detecting the imminent skid and causing a current command output (326) from the ForK (316) to be reduced to release braking force if the negative desired force command (322) minus a measured feedback force (332) is greater than a deadband of the ForK (316). A brake control system (100; 300) is also provided.