Rotorcraft Flight Control Transition Between TRC and Rate Modes

Solution Overview

Problem

Fly-by-wire systems in rotorcraft face challenges in smoothly transitioning between different control modes, leading to physical transients such as bumps or jolts during mode changes, which can affect pilot workload and passenger comfort.

Innovation Solution

The system transitions between translational rate command (TRC) mode and rate mode by fading out the gain of the attitude controller and decrementing the integrator value over specific periods, ensuring a smooth transition by maintaining a proportional path and increasing the gain of the control path between the cyclic controller and rate control block.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the control mode transitions abruptly between different control laws, then the transition speed is fast, but physical transients such as bumps or jolts occur during operation

Engineering Contradiction:

Improvetransition speedVSAvoidphysical transients (bumps or jolts)

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the controller output dynamic during mode transitions. Specifically, the controller output is adjusted based on the transition progress, allowing the system to adapt its response characteristics over time. This dynamic adjustment prevents abrupt changes that would cause physical transients while maintaining reasonable transition speed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the controller output parameter during mode transitions to smooth the transition process. By modifying the controller output parameter dynamically as the transition progresses, the system avoids sudden jumps in control signals that would manifest as bumps or jolts, thereby resolving the contradiction between fast transition and smooth operation.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the gain of the attitude controller is faded out quickly during mode transition, then the transition is faster, but instability or oscillation may occur

Engineering Contradiction:

Improvetransition speedVSAvoidcontrol stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The patent applies dynamics by making the controller output dynamic during mode transitions. Specifically, the controller output is adjusted based on the transition progress, allowing the system to adapt its response characteristics over time. This dynamic adjustment prevents abrupt changes that would cause physical transients while maintaining reasonable transition speed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses feedback by monitoring the transition progress and adjusting the controller output accordingly. The system continuously evaluates the transition state and modifies the controller output to maintain stability throughout the transition process, preventing oscillations while achieving smooth mode changes.

Inventive Principle:

Principle #23Feedback

3Loss of time

If the integrator value is decremented rapidly during mode transition, then the transition completes faster, but noticeable changes or transients may be perceived by the pilot

Engineering Contradiction:

Improvetransition timeVSAvoidnoticeable changes (bumps or jolts)

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the controller output dynamic during mode transitions. Specifically, the controller output is adjusted based on the transition progress, allowing the system to adapt its response characteristics over time. This dynamic adjustment prevents abrupt changes that would cause physical transients while maintaining reasonable transition speed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies beforehand cushioning by proactively adjusting the controller output during the transition process. The system anticipates potential transients and applies compensatory adjustments in advance, smoothing out the transition and preventing noticeable bumps or jolts that would be perceived by the pilot.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS11561539B2Aircraft control mode transition smoothing

Publication Date: 2023.01.24 TEXTRON INNOVATIONS INC

AI summary

In accordance with an embodiment, a method of operating an aircraft includes operating the aircraft in a first mode including determining an attitude based on a pilot stick signal, where a translational speed or an attitude of the aircraft is proportional to an amplitude of the pilot stick signal in the first mode; transitioning from the first mode to a second mode when a velocity of the aircraft exceeds a first velocity threshold; and operating the aircraft in the second mode where the output of the rate controller is proportional to the amplitude of the pilot stick signal.