Steer-By-Wire Joystick Sensitivity Switching for Fine Wheel Angle Control
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Solution Overview
Problem
When a joystick is used as an operating member in a steer-by-wire steering system, the large change in steered angle relative to the amount of operation makes fine adjustments difficult.
Innovation Solution
A steering control device with a power transmission path separation between an operation unit and a steering unit, incorporating a target steering corresponding value computing unit that adjusts sensitivity based on low sensitivity conditions to reduce the change in steered angle relative to the operation amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a joystick is used as the operating member to reduce the amount of operation, then the amount of operation necessary to turn the steered wheels is reduced, but the steered angle changes greatly even with small operation changes, making fine adjustments difficult
Solution Approach 1:
The steering control device dynamically changes the angle ratio between the operating lever and steered wheels based on detected steering angles. When the steering angle is within a predetermined range (near straight position), a first angle ratio is applied for fine adjustments. When outside this range, a second angle ratio (with larger absolute value) is applied for larger steering changes. This dynamic adjustment resolves the contradiction by adapting the transmission ratio to the current operating state.
Solution Approach 2:
The system changes the angle ratio parameter based on the steering angle condition. By switching between different angle ratio values (first angle ratio for small angles, second angle ratio for larger angles), the system optimizes both the ease of operation and fine adjustment capability according to the current steering state.
2Productivity
If the angle ratio is increased to reduce operation amount, then steering efficiency is improved, but control precision for fine adjustments is degraded
Solution Approach 1:
The angle ratio is dynamically adjusted based on the current steering angle. When the steering angle is small (within predetermined range), a smaller angle ratio is used to maintain control precision. When the steering angle is large, a larger angle ratio is used to improve steering efficiency. This dynamic parameter adjustment resolves the contradiction between productivity and precision.
Solution Approach 2:
Different angle ratios are applied in different steering angle ranges. The first angle ratio applies locally when the steering angle is within the predetermined range, while the second angle ratio applies when outside this range. This local differentiation allows optimal performance in each operating region.
Data Source
AI summary
A steering control device includes a target steering corresponding value computing unit configured to compute a target steering corresponding value. The target steering corresponding value computing unit is configured to execute low sensitivity determination processing for determining whether or not a low sensitivity condition for reducing an amount of change in the steered angle with respect to an amount of change in an amount of operation of an operating lever is satisfied, normal computation processing for computing the target steering corresponding value based on the amount of operation when the low sensitivity condition is not satisfied, and low sensitivity computation processing for computing, based on the amount of operation, the target steering corresponding value having a smaller absolute value than the target steering corresponding value computed by the normal computation processing, when the low sensitivity condition is satisfied.