MRF Joystick Stiffness Control for Adaptive Work Vehicle Operation

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Solution Overview

Problem

Existing work vehicle joystick systems lack advanced features to enhance safety and efficiency, particularly in dynamic operational environments, and fail to adapt effectively to varying tasks and conditions.

Innovation Solution

A magnetorheological fluid (MRF) joystick system with a controller architecture that can selectively alter joystick stiffness by varying the resistance force, allowing for modified stiffness modes based on joystick movement, implement type, and operational conditions, using a magnetorheological fluid resistance mechanism to adjust viscosity and resistance forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional fixed-stiffness joystick systems are used, then the system structure is simple, but the system cannot adapt to varying operational conditions and tasks

Engineering Contradiction:

Improveadaptability to varying tasks and conditionsVSAvoidsystem structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The joystick system transitions from fixed stiffness to variable stiffness through the MRF resistance mechanism, which can dynamically adjust resistance levels based on operational conditions. The controller receives input signals and modifies the magnetic field strength applied to the MRF, enabling real-time adaptation of joystick characteristics without mechanical reconfiguration.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the physical parameter of fluid viscosity through magnetic field application. The MRF's viscosity varies in response to magnetic field strength, allowing the resistance mechanism to provide different levels of resistance force. This parameter change enables adaptive joystick behavior across different operational modes without altering the mechanical structure.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If variable stiffness control is implemented, then operator control precision is improved, but the resistance mechanism complexity increases

Engineering Contradiction:

Improvecontrol precisionVSAvoidresistance mechanism complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system replaces traditional mechanical resistance mechanisms (springs, dampers, friction elements) with a magnetorheological fluid-based resistance mechanism. This substitution eliminates complex mechanical linkages and moving parts while achieving variable resistance through magnetic field control, thereby maintaining control precision with reduced mechanical complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The MRF acts as an intermediary between the magnetic field and the joystick resistance. The controller generates magnetic fields that modify the MRF's viscosity, which in turn adjusts the resistance force on the joystick. This intermediary approach enables precise control of resistance levels without direct mechanical actuation, simplifying the overall control mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If MRF resistance mechanism is used to vary joystick stiffness, then joystick behavior is enhanced, but the system cost increases

Engineering Contradiction:

Improvejoystick behaviorVSAvoidmanufacturing cost

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The MRF resistance mechanism serves multiple functions: providing resistance force, enabling variable stiffness control, and offering adaptive damping. This multi-functionality consolidates what would otherwise require separate mechanical components, potentially reducing overall system complexity and manufacturing costs despite the specialized MRF material.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 MRF joystick system improves operator control and safety by providing adaptable resistance levels, enhancing joystick behavior and functionality, allowing for precise control and efficient operation across different tasks and environments.

Implementation Method 1

An MRF joystick resistance mechanism is controllable to vary a joystick stiffness resisting movement of the joystick relative to the base housing

Methodology Applied

Scientific EffectMagnetorheological fluid effect: Magnetorheological Fluid

Data Source

PatentUS11499294B2Work vehicle magnetorheological fluid joystick systems operable in modified joystick stiffness modes

Publication Date: 2022.11.15 DEERE & CO

AI summary

Embodiments of a work vehicle magnetorheological fluid (MRF) joystick system include a joystick device having a base housing, a joystick movably mounted to the base housing, and a joystick position sensor configured to monitor joystick movement. An MRF joystick resistance mechanism is controllable to vary a joystick stiffness resisting movement of the joystick relative to the base housing, while a controller architecture is coupled to the joystick position sensor and to the MRF joystick resistance mechanism. The controller architecture is configured to: (i) selectively place the work vehicle MRF joystick system in a modified joystick stiffness mode during operation of the work vehicle; and (ii) when the work vehicle MRF joystick system is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism to vary the joystick stiffness based, at least in part, on the movement of the joystick relative to the base housing.