Bistable Shutoff Valve Signal Priority Control
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Solution Overview
Problem
Aircraft engine bistable actuators can be malfunction due to simultaneous receipt of contradicting control signals, leading to catastrophic thrust control malfunctions (TCM), which existing solutions address with costly and complex modifications or equipment, reducing system robustness and increasing in-flight shutdown rates.
Innovation Solution
A method for controlling a bistable shut-off valve in an aircraft engine using two control channels, where the amplitude of the closing signal is adjusted to constantly stress the pallet towards the closed position, and the opening signal oscillates between actuation and rest values, ensuring forces cancel out and maintaining the pallet stationary when both signals are received simultaneously, prioritizing the closing signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bistable actuator is controlled by several parallel control units via independent control channels, then the system reliability is improved through redundancy, but the actuator may receive contradicting signals simultaneously which causes malfunction
Solution Approach 1:
The patent introduces an intermediary mechanism (the oscillating opening signal) that mediates between the closing signal from one control channel and the potential contradicting opening signal from another channel. This intermediary approach allows the system to handle multiple control channels while preventing the harmful effect of simultaneous contradicting signals through the frequency-based discrimination mechanism
2Ease of operation
If a monostable actuator with mechanical priority on closing is used, then the priority of closing signal is ensured, but the system robustness is downgraded as the valve closes on many simple malfunctions
Solution Approach 1:
The patent changes the parameter of the opening signal from a simple binary state to an oscillating signal with specific frequency characteristics. This parameter change allows the system to distinguish between intentional opening commands and malfunction conditions, thereby maintaining closing priority without the excessive sensitivity that plagues monostable actuators
3Ease of operation
If a bistable actuator is supplied with contradicting control signals of different intensities, then the priority of the stronger signal is achieved, but the internal operation of the valve must be substantially modified
Solution Approach 1:
Instead of modifying the valve's internal operation to handle different signal intensities, the patent changes the temporal parameter of the opening signal, making it oscillate at a specific frequency. This approach achieves signal priority through frequency-based discrimination rather than intensity-based mechanisms, thereby avoiding substantial modifications to the valve's internal structure
Data Source
AI summary
There is proposed a method for controlling a bistable shutoff vale for an aircraft engine, involving the steps of: emitting a closure signal on one of the control channels—emitting an open signal on the other control channel, the method being characterized in that—the amplitude of the close signal is designed to cause the vane to move into a first position constantly in a given period of time,—in the same period, the amplitude of the open signal fluctuates between a value designed to urge the valve toward a second position and a rest value, the actuating values of the two signals being adapted to one another in order to keep the vane immobile when the two signals received by the valve simultaneously adopt said actuation values.