Variable Steering Ratio Control for Lateral Acceleration
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Solution Overview
Problem
Existing steering systems require hand switching to achieve maximum turning angle, leading to abrupt changes in turning angle, causing uncomfortable lateral acceleration for occupants due to high-frequency steering operations.
Innovation Solution
A steering system with an electronic control unit that adjusts the ratio of turning angle change to steering angle change and delay degree across different steering angle and vehicle speed areas, using a low-pass filter and rate limiter to reduce lateral acceleration while maintaining responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the gear ratio is decreased in the steering angle area near the lock position to enable turning without hand switching, then the maximum turning angle is achievable without hand switching, but the turning angle changes abruptly causing uncomfortable lateral acceleration
Solution Approach 1:
The patent applies dynamics by making the gear ratio variable rather than fixed. The electronic control unit dynamically adjusts the gear ratio based on the steering angle, using a smaller gear ratio near the lock position to enable maximum turning without hand switching, and a larger gear ratio near the neutral position to reduce abrupt turning changes and lateral acceleration.
Solution Approach 2:
The patent changes the gear ratio parameter according to the steering angle position. By setting different gear ratio values in different steering angle areas (smaller ratio near lock position, larger ratio near neutral position), the system achieves both maximum turning capability and reduced occupant discomfort.
2Speed
If the gear ratio is made variable to improve responsiveness, then the turning angle responsiveness improves, but the system complexity increases
Solution Approach 1:
The patent replaces a complex mechanical variable gear ratio system with an electronic control system. The electronic control unit calculates and applies appropriate gear ratio values based on steering angle feedback, achieving variable gear ratio functionality through software control rather than complex mechanical mechanisms.
Solution Approach 2:
The system uses dynamic adjustment of gear ratio through electronic control, allowing the gear ratio to change smoothly and continuously based on steering angle position, thereby improving responsiveness without requiring complex mechanical variable geometry mechanisms.
Data Source
AI summary
A steering system is configured such that a ratio of a turning angle change amount with respect to a steering angle change amount in a first steering angle area is larger than the ratio of the turning angle change amount with respect to the steering angle change amount in a second steering angle area, and a steering angle in the second steering angle is smaller than the steering angle of the first steering angle area. An electronic control unit of the steering system sets a delay degree of a change in turning angle with respect to a change in steering angle in the first steering angle area to be larger than the delay degree of the change in turning angle with respect to the change in steering angle in the second steering angle area regardless of a turning-over operation or a turning-back operation.