Aircraft Flight Control Surface Coordination for Flexible Mode Mitigation
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Solution Overview
Problem
Aircraft-pilot coupling (APC) events occur due to unwanted aircraft motions caused by interactions between the pilot and the aircraft, leading to instabilities in the closed-loop feedback control system, affecting passenger comfort and aircraft control, particularly when pilot commands excite structural flexible modes of the aircraft.
Innovation Solution
A system that uses first and second flight control surfaces to mitigate the effects of structural flexible mode excitation by executing a mitigating command of zero magnitude and duration when a pilot command is likely to excite a flexible mode, utilizing a controller with programmed criteria and transfer functions to apply appropriate commands based on operational conditions such as altitude, speed, and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pilot commands are executed without modification, then aircraft responsiveness and pilot control authority are maintained, but structural flexible modes may be excited causing aircraft-pilot coupling events and instability
Solution Approach 1:
The flight control system acts as an intermediary between the pilot and the aircraft structure. The controller monitors pilot commands and automatically applies mitigating commands to counteract excitation of structural flexible modes, thereby preventing aircraft-pilot coupling events while preserving pilot control authority without modification
Solution Approach 2:
The system uses feedback from command characteristics (frequency, magnitude) to determine when structural flexible modes are likely to be excited. Based on this feedback, the controller automatically adjusts control surface commands to mitigate instability while maintaining normal pilot control
2Reliability
If mitigating commands are applied to counteract structural flexible mode excitation, then aircraft-pilot coupling events are reduced and control stability is improved, but additional control surface activity is introduced
Solution Approach 1:
The system applies partial action by only introducing mitigating commands when and where needed to counteract specific excitation conditions. The controller evaluates command characteristics and applies minimal necessary corrections rather than continuous complex control, reducing overall control surface activity while maintaining stability
3Reliability
If the mitigating command is applied continuously, then structural flexible mode excitation is suppressed, but unnecessary control activity increases and may interfere with normal aircraft operations
Solution Approach 1:
The system uses periodic evaluation of command characteristics to determine when mitigating commands are needed. Rather than continuous application, the controller periodically assesses whether pilot commands are likely to excite structural modes and applies mitigating commands only during these specific periods, reducing unnecessary control activity and energy consumption
Data Source
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AI summary
Systems and methods for controlling a fixed-wing aircraft during flight are disclosed. The aircraft comprises first and second flight control surfaces of different types. The method comprises determining that a pilot command of the first flight control surface will excite a structural flexible mode of the aircraft and then executing the pilot command of the first flight control surface in conjunction with a command of the second flight control surface to mitigate the effect of the excitation of the structural flexible mode of the aircraft.