Rotorcraft Fly-By-Wire Control Using Rate-Based Attitude Estimation
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Solution Overview
Problem
As rotorcraft become larger and more complex, the differences between flying rotorcraft and fixed-wing aircraft become more pronounced, with tightly coupled flight parameters and controls, making it challenging to maintain stable flight characteristics across various speed regimes, especially in transitioning between hover and cruising speeds.
Innovation Solution
The implementation of a fly-by-wire (FBW) system with flight control computers that decouple physical flight characteristics, providing automated adjustments to pilot inputs, allowing for stable flight while maintaining intuitive control, by using rate sensors to estimate angular positions and filter signals for accurate flight control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotorcraft uses traditional control systems with absolute attitude sensors, then the system can provide direct angular position measurements, but the system complexity increases and reliability decreases due to sensor limitations in certain flight regimes
Solution Approach 1:
The patent introduces rate sensors as an intermediary measurement device that indirectly provides angular position information through integration of angular velocity data. This intermediary approach avoids the direct measurement limitations of absolute attitude sensors while maintaining measurement precision across all flight regimes including hover and high-speed flight.
Solution Approach 2:
The patent replaces the mechanical absolute attitude sensor system with an electronic integration system using rate sensors. This substitution eliminates the mechanical limitations and complexity of absolute sensors while providing reliable angular position estimation through computational integration of rate data.
2Adaptability or versatility
If a rotorcraft transitions between hover and cruising speeds, then the flight regime changes require different control characteristics, but maintaining stable flight characteristics becomes difficult due to tightly coupled flight parameters
Solution Approach 1:
The patent implements a dynamic control system that automatically adapts control characteristics based on the current flight regime. The control system modifies gain schedules and control law parameters in real-time as the rotorcraft transitions between hover, low-speed, and high-speed flight, maintaining stable flight characteristics across all regimes without requiring manual pilot intervention.
Solution Approach 2:
The patent changes control system parameters such as gain values and filter characteristics based on flight regime detection. By dynamically adjusting these parameters, the system maintains optimal stability and responsiveness across different speed regimes, resolving the contradiction between adaptability and stability.
3Reliability
If a rotorcraft uses rate sensors to estimate angular positions, then the measurement reliability improves across all flight regimes, but the system requires additional signal filtering and processing complexity
Solution Approach 1:
The patent implements feedback control using rate sensor measurements that are integrated to provide angular position estimates. The filtered angular position feedback is used in the control law to generate appropriate control signals, creating a closed-loop system that improves reliability while managing processing complexity through efficient feedback architecture.
Solution Approach 2:
The patent applies signal filtering with dynamically adjusted parameters based on flight regime. By changing filter characteristics such as cutoff frequencies and integration time constants according to the current flight conditions, the system maintains measurement reliability while optimizing processing efficiency and reducing unnecessary complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The FBW system enhances flight stability and reduces pilot workload by automatically adjusting controls, ensuring stable flight characteristics across different speed regimes and improving handling qualities by using estimated angular positions from rate sensors, which are more reliable than absolute attitude sensors.
Implementation Method 1
obtain a first signal from a first sensor of the rotorcraft, the first signal indicative of an angular velocity around a first axis of the rotorcraft
Implementation Method 2
filter the first signal with a first filter to estimate an angular position around the first axis of the rotorcraft
Data Source
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AI summary
In an embodiment, a method (401) includes: obtaining a first signal from a first sensor of a rotorcraft, the first signal indicating measured angular velocity around a first axis of the rotorcraft (403); filtering the first signal with a lag compensator to estimate angular position around the first axis of the rotorcraft (405); and adjusting flight control devices of the rotorcraft according to the estimated angular position and the measured angular velocity around the first axis of the rotorcraft, thereby changing flight characteristics of the rotorcraft around the first axis of the rotorcraft.