Mini-Stick Magnetorheological Brake for Reliable Haptic Feedback

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Solution Overview

Problem

Aircraft piloting devices lack reliable mechanical feedback in case of electrical or mechanical failures, leading to safety concerns and ergonomic issues due to complex and bulky systems with limited angular travel and high electricity consumption.

Innovation Solution

A mini-piloting handle system incorporating a rheological brake with an electromagnetic field control device that provides a direct and efficient resistive torque to the lever, eliminating the need for mechanical transmission organs and reducing size and weight, while ensuring continuous haptic feedback even in failure scenarios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If passive mechanical systems or active electromechanical systems are used to provide force feedback, then haptic feedback is restored, but the system becomes bulky, complex, and expensive

Engineering Contradiction:
Improvehaptic feedback reliabilityVSAvoidsystem complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical transmission systems (gears, clutches, torque limiters) with a magnetorheological brake system that uses magnetic field control to generate force feedback. The magnetorheological fluid changes its viscosity in response to magnetic fields, allowing direct torque application to the lever without mechanical transmission organs, thereby simplifying the overall system architecture while maintaining force feedback functionality

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes the variable viscosity property of magnetorheological fluid by changing its rheological parameters through magnetic field application. The fluid transitions from a low-viscosity state during normal operation to a high-viscosity state during failure conditions, enabling the same component to serve multiple functions across different operating conditions without requiring complex mechanical changes

Inventive Principle:
Principle #35Parameter changes

2Reliability

If mechanical linkages are used to connect piston dampers to the lever, then force feedback is provided, but the angular travel is limited and ergonomics are reduced

Engineering Contradiction:
Improveforce feedbackVSAvoidangular travel
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent eliminates mechanical linkages such as connecting rods and gear trains by using a magnetorheological brake that applies torque directly to the lever through magnetic field interaction. This direct-acting mechanism allows the lever to achieve full angular travel without the constraints imposed by mechanical transmission components, significantly improving ergonomics while maintaining force feedback capability

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If electrorheological or magnetorheological fluids are used in piston dampers, then force feedback is enhanced, but particle stratification occurs reducing component lifespan

Engineering Contradiction:
Improveforce feedback enhancementVSAvoidcomponent lifespan
Core Design Contradiction:
ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent replaces the piston damper architecture with a magnetorheological brake system where the fluid is contained in a stationary housing and subjected to rotational magnetic fields. This eliminates the reciprocating motion that causes particle stratification in piston dampers, as the magnetic field continuously agitates the fluid particles, maintaining uniform distribution and extending component lifespan while preserving force feedback enhancement

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs periodic rotational magnetic fields to continuously agitate the magnetorheological fluid particles, preventing them from settling or stratifying. The alternating magnetic field directions and rotations ensure uniform particle distribution throughout the fluid volume, thereby maintaining consistent fluid properties and extending the operational life of the brake components

Inventive Principle:
Principle #19Periodic action

4Force

If intermediate gears are used in magnetorheological brakes, then torque is transmitted to the lever, but the system becomes more complex and dynamic performance is reduced

Engineering Contradiction:
Improvetorque transmissionVSAvoidgear train complexity
Core Design Contradiction:
ForceVSDevice complexity

Solution Approach 1:

The patent eliminates intermediate gears and mechanical transmission organs by using a magnetorheological brake that applies torque directly to the lever through magnetic field interaction with the fluid. The variable viscosity of the magnetorheological fluid allows direct torque transmission without mechanical intermediaries, simplifying the system architecture, reducing the number of components, and improving dynamic response while maintaining effective torque transmission to the lever

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 system enhances safety and ergonomics by providing consistent haptic feedback, reducing the risk of pilot error and improving reliability with reduced size, weight, and energy consumption, while avoiding particle stratification and extending the lifespan of the brake components.

Implementation Method 1

a magnetorheological brake (5a, 5b) linked to said roll axis and to said pitch axis respectively, said magnetorheological brake comprising a magnetic field control device configured to apply a magnetic field to a magnetorheological fluid

Methodology Applied
Scientific EffectMagnetorheological effect: Magnetorheological Fluid

Implementation Method 2

an electromagnetic field control device that provides a direct and efficient resistive torque to the lever

Methodology Applied
Scientific EffectElectromagnetic field generation: Electromagnetic Induction

Data Source

PatentEP3850459B1Force application device for an active mini-stick and mechanical backup control method
Publication Date: 2025.02.12 SAFRAN ELECTRONICS & DEFENSE (FR)
  • EP3850459B1 patent drawingFigure 1
  • EP3850459B1 patent drawingFigure 2
  • EP3850459B1 patent drawingFigure 3

AI summary

The invention concerns a force application device for an aircraft control stick, the device comprising: a mechanical joint (2) configured to receive a lever (1) of an aircraft control stick, a force motor (3a) comprising a drive shaft extending along a third axis (A), the rotation of the drive shaft being linked to the rotation of the mechanical joint (2) about the roll axis or the pitch axis, a rheological brake (5a) comprising a space (53) delimited by two opposing parts (52a, 52b), the space being suitable for containing a rheological material, one (52a) of the two parts being arranged on the drive shaft and being able to rotate about the third axis (A) with respect to the other (52b), a control device (54) controlled to apply an electromagnetic field inside the space (53) so as to vary a shear strength of the rheological material.