Wheel Loader Joystick Center Shift for Stable Steering Feedback
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Solution Overview
Problem
Existing control systems for work machines, such as wheeled loaders, experience irregular movements and unwanted effects on control behavior due to the lack of elasticity in feedback mechanisms, leading to 'stick-slip' effects and hazardous situations.
Innovation Solution
An adjustment device is introduced to shift the central position of the spring assembly within the sensor measurement range, incorporating a self-inhibiting transmission and optional active or passive drive elements to maintain steering capability even when the spring assembly reaches maximum deflection, eliminating the need for separate braking elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic powder brake is used to suppress lever excursion, then steering safety is improved, but stick-slip effects occur causing irregular movements and unwanted control behavior
Solution Approach 1:
The patent replaces the magnetic powder brake (mechanical/friction-based system) with an electric drive system that uses electromagnetic forces to apply restoring force to the operating lever. This substitution eliminates the stick-slip effects inherent in friction-based braking while maintaining the ability to suppress unwanted lever excursions and improve steering safety.
Solution Approach 2:
The patent implements a feedback control system where the actual lever position is continuously monitored and compared with the desired position. The electric drive adjusts the restoring force in real-time based on the deviation detected, enabling precise control that prevents stick-slip effects while maintaining steering safety through active correction rather than passive friction-based suppression.
2Reliability
If an electric drive replaces the spring mechanism, then steering safety is improved, but unwanted lever excursion due to control errors can occur
Solution Approach 1:
The patent incorporates redundancy and fail-safe mechanisms in the electric drive system. The restoring force characteristic is designed to ensure that even in case of control errors or drive failures, the system defaults to a safe state that prevents unwanted lever excursions. The spring mechanism provides a passive backup that ensures basic restoring function even if the active electric drive fails.
Solution Approach 2:
The electric drive system is designed to autonomously detect and correct control errors through continuous monitoring of lever position and drive status. When control errors are detected, the system automatically adjusts the restoring force to prevent unwanted lever excursion, eliminating the need for external intervention while maintaining steering safety.
3Loss of information
If the restoring force is increased to indicate overload, then feedback to the user is improved, but control precision deteriorates due to excessive force
Solution Approach 1:
The patent implements a dynamic restoring force characteristic where the magnitude of the restoring force varies based on the operating conditions and detected overload levels. During normal operation, the restoring force provides gentle feedback for precise control. When overload is detected, the restoring force is increased to provide noticeable feedback to the user about the overload condition, while the system maintains the ability to return to precise control once the overload is resolved.
Solution Approach 2:
The patent changes the parameters of the restoring force based on the operational state. The electric drive adjusts the restoring force magnitude dynamically - using lower force values for normal precision control and higher force values when overload feedback is needed. This parameter adaptation allows the system to provide adequate user feedback without permanently degrading control precision.
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
This solution prevents irregular movements and maintains steering capability in both directions, ensuring safe and stable control behavior by allowing travel beyond maximum positions through correction angles, reducing residual deflection and avoiding unwanted steering movements.
Implementation Method 1
having at least one restoring device in the form of one or more spring assemblies that are connected to the manual control device such that a restoring force is exerted on the manual control device by the spring assembly when the spring assembly is not in its central position
Data Source
AI summary
The invention relates to a system for controlling a work machine, in particular a wheel loader, having at least one hand-held control device (6), in particular a joystick or steering wheel, at least one restoring device (8) in the form of one or more spring assemblies, which are connected to the hand-held control device in such a way a restoring force is exerted upon the hand-held control device by the spring assembly when said spring assembly is not in the central position. An adjusting device (9, 12, 13) which engages with the spring assembly such that an adjustment of the central position of the spring assembly can be carried out, is provided.