Wheel Loader Joystick Steering with Adjustable Counterforce
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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 speed reduction ratios, leading to oversized motors and difficulty in adjusting the operation unit's size to fit user body types.
Innovation Solution
A work vehicle design incorporating a hydraulic actuator, actual steering angle detection, an operating unit with a support and biasing mechanism, and a position adjustment control system to manage the joystick lever's rotation angle, allowing for reduced size and improved operational feel without large motors.
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 operation unit size increases making it difficult to adjust to user body types
Solution Approach 1:
The patent applies dynamics by making the speed reduction ratio variable rather than fixed. The speed reducer's reduction ratio is dynamically adjusted based on the operation state, allowing the system to provide high counterforce torque when needed while maintaining ease of operation during normal use. This resolves the contradiction by enabling the system to adapt its mechanical characteristics in real-time rather than being constrained by a fixed reduction ratio.
Solution Approach 2:
The patent changes the parameter of speed reduction ratio from a constant value to a variable parameter that can be adjusted according to operational requirements. By controlling the speed reducer to provide different reduction ratios in different operating conditions, the system can optimize both the counterforce torque output and the operational ease, resolving the technical contradiction between these two opposing requirements.
2Power
If a large-scale motor is used to provide sufficient torque without speed reducer, then the torque requirement is met, but the operation unit size increases making position adjustment difficult
Solution Approach 1:
The patent uses a dynamic speed reduction mechanism that adjusts the reduction ratio based on operational needs. This allows the use of a smaller motor compared to a fixed high-reduction-gear system, while still achieving the required torque output when needed. The dynamic adjustment enables the system to maintain compact dimensions while providing sufficient power on demand.
Solution Approach 2:
The speed reducer is designed to provide preliminary mechanical advantage before the motor needs to deliver full torque. By pre-configuring the reduction mechanism to engage only when additional torque is required, the system can use a smaller motor while still meeting peak torque requirements, thereby reducing the overall operation unit size.
3Power
If the speed reduction ratio is increased to reduce motor size, then the motor scale decreases, but the operational counterforce becomes excessively large
Solution Approach 1:
The patent implements a dynamic speed reduction system where the reduction ratio is continuously adjusted based on operational conditions. This allows the system to use a smaller motor while preventing excessively large operational counterforce by reducing the reduction ratio when high torque is not needed. The dynamic control ensures optimal balance between motor size and operational ease throughout the operating range.
Solution Approach 2:
The speed reduction ratio is changed from a fixed parameter to a variable parameter that can be optimized for different operating conditions. This enables the system to achieve compact motor dimensions while maintaining acceptable operational counterforce levels by adjusting the reduction ratio according to the specific task requirements.
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 enables a compact operation unit with effective counterforce management, enhancing user experience and adaptability to different user sizes by reflecting the actual steering angle in the joystick lever's position, thus reducing the need for oversized motors.
Implementation Method 1
a hydraulic actuator, and performs a steering operation
Implementation Method 2
The biasing part biases the operating part to a predetermined position with respect to the rotating part
Data Source
Figure 1
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Figure 3
AI summary
In a wheel loader (1) of the present embodiment, a support part (42) rotatably supports a joystick lever (51). A base plate (71) is rotatably supported by the support part (42). A biasing part (44) biases the joystick lever (51) to a predetermined position with respect to the base plate (71). A position adjusting part (45) adjusts the rotation angle of the base plate (71) with respect to the support part (42). A lever absolute angle sensor (26) detects a detection value θi_detect of a lever angle of the joystick lever (51) with respect to the support part (42). A motor drive control part (110) controls the position adjusting part (45) based on the detection value θs_detect of a vehicle body frame angle. A steering control part (120) controls steering cylinders (21, 22) based on the difference between a detection value θic_detect of a converted lever angle corresponding to the detection value θi_detect of the lever angle, and a detection value θs_detect of the vehicle body frame angle.