Joystick Steering Unit With Variable Counterforce for Work Vehicles
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Solution Overview
Problem
In steer-by-wire systems using a joystick lever, achieving a suitable counterforce torque is challenging due to increased operational counterforce with higher speed reduction ratios, leading to larger motors and size issues with the operating unit, making it difficult to adjust for user comfort and space constraints.
Innovation Solution
A work vehicle with a hydraulic actuator, actual steering angle detecting part, operating unit, position adjustment control, and steering control part, where the biasing part adjusts counterforce based on relative angles to provide a reduced operating unit size and enhanced operator feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the speed reduction ratio is increased to produce sufficient counterforce torque, then the counterforce torque increases, but the operational counterforce becomes too large and the motor size increases
Solution Approach 1:
The patent applies dynamics by making the counterforce characteristic variable through a nonlinear spring mechanism. The spring is designed with varying stiffness along its compression range, providing low counterforce during initial operation and high counterforce during large-angle deflections. This dynamic adjustment of force characteristics resolves the contradiction between needing sufficient counterforce torque and maintaining ease of operation.
Solution Approach 2:
The patent changes the physical parameter of spring stiffness by using a nonlinear spring with varying cross-sectional area or wire diameter along its length. This parameter variation allows the spring to provide different force characteristics at different compression levels, enabling low operational counterforce at small angles while generating high counterforce torque at large angles without requiring a large-scale motor.
2Power
If a large-scale motor is used to provide sufficient torque with reduced speed reduction ratio, then the torque requirement is met, but the operating unit size increases and position adjustment becomes difficult
Solution Approach 1:
The patent replaces the conventional motor-driven speed reduction system with a passive mechanical spring mechanism. Instead of using a large-scale motor with gear reduction to generate counterforce torque, the invention uses the elastic potential energy storage and release characteristics of a nonlinear spring to provide the required torque. This substitution dramatically reduces the size of the operating unit while maintaining the necessary torque characteristics.
3Force
If the speed reduction ratio is increased, then the counterforce torque increases, but the friction torque and cogging torque of the motor increase
Solution Approach 1:
The patent eliminates the motor and speed reduction mechanism entirely, replacing them with a direct mechanical spring connection to the operating lever. This substitution removes the sources of friction torque and cogging torque associated with motor bearings, gear meshes, and other mechanical transmission elements. The spring mechanism provides torque through elastic deformation without the energy losses inherent in motor-driven systems.
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 solution allows for a compact operating unit that provides necessary counterforce feedback to the operator, improving user experience and ease of operation while reducing the size and complexity of the system.
Implementation Method 1
The biasing part biases the operating part to a predetermined position with respect to the rotating part
Data Source
AI summary
A work vehicle includes a hydraulic actuator that changes an actual steering angle, an actual steering angle detecting part, an operating unit that performs a steering operation, a position adjusting control part that controls the position adjusting part based on the actual steering angle, and a steering control part that controls the hydraulic actuator. The operating unit includes a support part, a rotating part supported rotatably by the support part, an operating part supported rotatably by the support part or the rotating part, a biasing part that biases the operating part to a predetermined position with respect to the rotating part, and a position adjusting part that adjusts a rotation angle of the rotating part with respect to the support part. The biasing part may produce various counterforces and may increase or reduce an increasing rate of a counterforce with respect to the relative angle.