Joystick Counterforce Control in Wheel Loader Steer-by-Wire
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Solution Overview
Problem
In steer-by-wire systems using a joystick lever, achieving sufficient counterforce torque is challenging due to increased operational counterforce when the speed reduction ratio is increased, leading to larger motor sizes and difficulty in adjusting the operating unit to fit user body types.
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 an optimal operational feel without excessive size or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the speed reduction ratio is increased to achieve sufficient counterforce torque, then the counterforce torque increases, but the operational counterforce becomes too large and the motor size increases
Solution Approach 1:
The biasing part dynamically adjusts the counterforce characteristics based on the operating conditions. When the operating part is at neutral position, the biasing part provides minimal counterforce for easy positioning. When the operating part is displaced from neutral, the biasing part progressively increases counterforce to provide operational feel and precision control, resolving the contradiction between sufficient counterforce torque and ease of operation.
Solution Approach 2:
The system changes the counterforce parameter dynamically based on the position of the operating part. The biasing part is configured to provide different counterforce levels at different positions: minimal counterforce at neutral position for easy adjustment, and increased counterforce during operation for precision control. This parameter change resolves the contradiction by providing context-appropriate counterforce levels.
2Ease of operation
If a large-scale motor is used to provide sufficient torque without speed reducer, then the counterforce can be reduced, but the operating unit increases in size and becomes difficult to adjust for different users
Solution Approach 1:
The biasing part creates a dynamic counterforce system that provides sufficient torque only when needed during operation, rather than requiring constant high torque capability. This allows the use of a smaller motor that can be easily positioned and adjusted for different users, while still providing adequate counterforce during actual steering operations.
Solution Approach 2:
The counterforce function is segmented into different operational phases: positioning phase (minimal counterforce for ease of adjustment) and operation phase (increased counterforce for precision control). This segmentation allows the motor to be sized for the more demanding operation phase while benefiting from the easier positioning during adjustment, resolving the size-adjustability contradiction.
3Force
If the speed reduction ratio is increased, then the counterforce torque increases, but the friction torque and cogging torque of the motor increase due to the speed reducer
Solution Approach 1:
The patent extracts the speed reducer from the system and replaces it with a biasing part that directly generates counterforce torque. This eliminates the intermediate mechanical transmission stage that causes friction and cogging losses, while still achieving the required counterforce torque through direct biasing forces applied to the operating part.
Solution Approach 2:
The mechanical speed reduction system is replaced with a biasing mechanism that directly provides counterforce. This substitution eliminates the mechanical losses associated with gear friction and cogging effects, while maintaining the necessary counterforce torque through direct force application rather than torque multiplication.
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 configuration allows for a reduced-sized operating unit that provides the necessary counterforce and operational feel, enabling operators to effectively interact with the vehicle while accommodating different user body types.
Implementation Method 1
the biasing part increases the increasing rate of a counterforce with respect to the relative angle
Data Source
Figure 1
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AI summary
In a wheel loader (1) of the present embodiment, when a joystick lever (51) is operated and rotated to the right or left direction with respect to a base plate (71), a biasing part (44) produces a counterforce that corresponds to an absolute value of a lever relative angle θd when the absolute value of the lever relative angle θd of the joystick lever (51) with respect to the base plate (71) is less than an angle θ2, increases the counterforce up to F2 when the absolute value of the lever relative angle θd is the angle θ2, and after the counterforce at the angle θ2 has increased to F2, produces a counterforce that corresponds to the lever relative angle θd.