Aircraft Redundancy Voting Circuit for Two-Controller Failure
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Solution Overview
Problem
Existing redundancy control devices for aircraft fail to ensure reliable output when two controllers fail, as the final output depends on the similarity of outputs from faulty controllers, leading to potential instability and complexity in monitoring controller configurations.
Innovation Solution
A redundancy control device with three controllers, each outputting a first or second voltage, featuring comparison circuits, switches, and a majority voting circuit that uses a second voltage when a mismatch is detected, ensuring reliable output even if two controllers fail, without the need for monitoring controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If monitoring controllers are provided for each of the three controllers to detect failures, then the reliability of the final output is improved, but the device complexity increases and the monitoring controllers are prone to failures
Solution Approach 1:
Each controller performs self-diagnosis by comparing its own status signals with those of other controllers through comparison circuits. The controllers autonomously detect their own failure conditions without requiring external monitoring controllers, thereby improving reliability while reducing system complexity.
Solution Approach 2:
The comparison circuits continuously compare status signals from different controllers and provide feedback to switch control units. When a mismatch is detected, the feedback triggers the switch to disconnect the faulty controller's output line, ensuring the majority voting circuit receives only valid signals from healthy controllers.
2Reliability
If two controllers fail in the redundancy control device, then the reliability of the final output cannot be secured, as the final output determined by majority voting changes depending on whether outputs of the two faulty controllers are identical
Solution Approach 1:
The switch disconnects the output line of the faulty controller from the majority voting circuit when failure is detected. This extraction of the faulty signal prevents it from influencing the final output, ensuring that the majority voting circuit receives only valid signals from healthy controllers and produces a stable, reliable output.
Solution Approach 2:
The switch acts as an intermediary between the controller and the majority voting circuit. It mediates the signal transmission by either connecting or disconnecting the controller's output line based on the comparison result, thereby controlling whether the controller's signal influences the final output.
3Reliability
If the voltage supply unit supplies the second voltage to the output line when the first voltage from the controller is lost, then the latch circuit can latch the second voltage and keep outputting it, but this requires additional voltage supply capability
Solution Approach 1:
The voltage supply unit is pre-configured to supply the second voltage to the output line when the first voltage from the controller is lost. This beforehand cushioning ensures that the output line maintains a valid voltage level even when the controller fails, preventing signal loss and ensuring the latch circuit can maintain its state.
Data Source
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AI summary
The redundancy control device (350, 450) includes three controllers (11, 12, 13) that output status signals (N1, N2, N3), a majority voting circuit (70) to which a first voltage or a second voltage is supplied as an output signal (T) through an output line (91, 92, 93) of each controller, a switch (41, 42, 43) provided in each output line, a voltage supply unit (51, 52, 53) provided for each output line to supply the second voltage to the output line when the first voltage is lost, a latch circuit (61, 62, 63) provided for each output line to latch the second voltage when the second voltage is supplied thereto and continue to output the second voltage, a comparison circuit (31, 32, 33) provided for each controller to output a comparison signal (C) based on a comparison of the status signals, and a switch control unit (81, 82, 83) provided for each switch to outputs a switch signal (K) to the switch in response to the comparison signal from the comparison circuit.