Rotorcraft Vertical Speed Estimation for Stable FBW Control
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Solution Overview
Problem
Rotorcrafts face challenges in maintaining stable flight characteristics across different speed regimes due to tightly coupled flight parameters, requiring advanced flight control systems that decouple physical characteristics and reduce pilot workload, especially as they become larger and more complex.
Innovation Solution
The implementation of a fly-by-wire (FBW) system with flight control computers that integrate sensor signals, including pitot tubes and accelerometers, to estimate airspeed and adjust control inputs, using complementary filtering to improve accuracy and stability, and adjust control sticks intuitively to assist pilots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pilot manually balances engine power, main rotor collective thrust, main rotor cyclic thrust and tail rotor thrust, then the rotorcraft can be controlled in flight, but the pilot workload is high and stabilizing the rotorcraft becomes difficult
Solution Approach 1:
The flight control system automatically performs the balancing of engine power, main rotor collective thrust, main rotor cyclic thrust and tail rotor thrust without requiring continuous manual intervention from the pilot. The system serves itself by using sensors to detect flight parameters and automatically adjusting control surfaces and engine power to maintain stable flight, thereby reducing pilot workload while managing the complexity through automation.
Solution Approach 2:
The patent replaces manual mechanical control with an automated fly-by-wire flight control system that uses electronic sensors and computer processing. Instead of the pilot directly manipulating control surfaces and engine power through mechanical linkages, the system uses electronic signals to actuate controls based on sensor feedback, reducing the physical and cognitive workload on the pilot while managing system complexity through integrated electronics.
2Reliability
If the rotorcraft becomes larger and more complex, then the flight parameters become more tightly coupled, but this makes it harder to maintain stable flight characteristics across different speed regimes
Solution Approach 1:
The flight control system continuously monitors flight parameters using sensors and automatically adjusts control inputs to maintain stable flight characteristics. The system uses feedback from sensors detecting airspeed, altitude, and other flight parameters to make real-time adjustments to engine power and control surfaces, ensuring stable flight across different speed regimes despite the tightly coupled parameters resulting from the rotorcraft's size and complexity.
Solution Approach 2:
The patent implements a dynamic flight control system that adapts its control strategy based on the current flight regime and speed. The system continuously adjusts control gains and parameters to optimize stability across different operating conditions, allowing the rotorcraft to maintain stable flight characteristics whether hovering, cruising at low speed, or flying at high speed, despite the complex interactions between flight parameters.
3Measurement precision
If traditional airspeed measurement methods are used, then the measurements may be inaccurate during rapid deceleration, but using multiple sensors and filtering algorithms increases system complexity
Solution Approach 1:
The patent combines multiple sensor signals including pitot tube airspeed measurements and accelerometer data to determine accurate airspeed. By merging these different measurement sources and using filtering algorithms to process the combined signals, the system achieves high measurement precision even during rapid deceleration maneuvers where traditional single-sensor methods fail, while managing the complexity through integrated signal processing.
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 providing intuitive control adjustments and accurate airspeed estimation, improving rotorcraft performance across various flight regimes.
Implementation Method 1
a first aircraft sensor, such as a pitot tube, that measures a raw airspeed of the rotorcraft
Implementation Method 2
a second aircraft sensor, such as an accelerometer, that measures a raw forward acceleration of the rotorcraft
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
In an embodiment, a rotorcraft (101) includes: a flight control computer (205) configured to: receive a first sensor signal from a first aircraft sensor (207) of the rotorcraft; receive a second sensor signal from a second aircraft sensor (207) of the rotorcraft, the second aircraft sensor being different from the first aircraft sensor; combine the first sensor signal and the second sensor signal with a complementary filter (403) to determine an estimated vertical speed of the rotorcraft; adjust flight control devices of the rotorcraft according to the estimated vertical speed of the rotorcraft, thereby changing flight characteristics of the rotorcraft; and reset the complementary filter in response to detecting the rotorcraft is grounded.