Fly-by-wire Control Laws for Rotorcraft Motion Decoupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rotorcraft flight control systems face challenges in decoupling aircraft motions, leading to increased pilot workload due to inherent coupling of flight dynamics, which existing feedback loops fail to adequately address, especially in aircraft with canted tail rotors.
Innovation Solution
The implementation of a fly-by-wire control system with feed-forward control crossfeeds and washout mechanisms that anticipate and mitigate coupled aircraft motions, using high-pass filters and limiter circuits to process pilot inputs and adjust flight control commands, allowing the system to decouple aircraft motions and reduce pilot workload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If feedback loops are used to address coupled aircraft motions, then pilot workload is reduced, but the coupling effects are not adequately eliminated especially in aircraft with canted tail rotors
Solution Approach 1:
The patent applies preliminary action by using feed-forward control crossfeeds that anticipate coupled aircraft motions before they occur. The washout filter processes pilot inputs to predict coupling effects and generate compensating commands in advance, rather than relying solely on feedback loops that react after coupling effects manifest. This proactive approach adequately eliminates coupling effects especially in aircraft with canted tail rotors.
2Ease of operation
If washout filter is applied to decouple aircraft motions, then transient motion feedback is minimized, but steady-state position reflection may be delayed
Solution Approach 1:
The patent applies dynamics by making the washout filter characteristics adaptive rather than fixed. The filter dynamically adjusts its washout rate based on flight conditions, allowing faster washout during transient maneuvers when rapid decoupling is needed, and slower washout during steady-state flight when accurate position reflection is prioritized. This dynamic adjustment optimizes both transient response and steady-state accuracy.
3Reliability
If feed-forward control crossfeeds are implemented, then coupled aircraft motions are anticipated and offset, but system complexity increases
Solution Approach 1:
The patent applies the intermediary principle by introducing a washout filter as a mediating element between pilot inputs and the feed-forward control crossfeeds. The washout filter processes and shapes the pilot's control inputs before they are fed forward to generate decoupling commands, simplifying the overall system architecture. This intermediary approach maintains effective motion decoupling while managing system complexity through a unified filter-based control structure.
Data Source
AI summary
A flight control system includes a pilot control module configured to receive commands from a pilot, a flight control module operable to transmit an instruction to change at least one operating condition of an aircraft, and a flight control computer in communication between the flight control module and the pilot control module. The flight control computer is configured to receive a pilot command to change a first flight characteristic, wherein changing the first flight characteristic would result in an expected change to a second flight characteristic. The flight control computer may instruct the flight control module to transmit an instruction to change a first operating condition of the aircraft and instruct the flight control module to transmit an instruction to change a second operating condition of the aircraft to at least partially offset the expected change to the second flight characteristic.