Steer-By-Wire Reaction Force Control for Excessive Wheel Turning
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Solution Overview
Problem
Steer-by-wire steering systems face challenges in suppressing excessive turning of the wheel during rapid steering, as the turning angle can become excessively large due to a higher ratio of turning angle to steering angle, leading to ineffective cornering force and delayed return of the wheel.
Innovation Solution
A steer-by-wire steering apparatus with a reaction force actuator that applies an end steering reaction force when the steering angle approaches the end of a narrowed virtual steering range, based on turning angle velocity or steering angle velocity exceeding predetermined values, to prevent excessive turning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the turning angle ratio is increased in steer-by-wire system, then the steering responsiveness is improved, but excessive turning occurs during rapid steering maneuvers
Solution Approach 1:
The virtual steering range is dynamically adjusted based on steering angle velocity. During rapid steering maneuvers when the steering angle velocity exceeds a predetermined threshold, the virtual steering range is narrowed to prevent excessive turning. This dynamic adaptation allows the system to maintain high steering responsiveness during normal operation while ensuring turning control accuracy during rapid maneuvers.
2Ease of operation
If the steering reaction force is increased in nonlinear region, then excessive steering manipulation is suppressed, but excessive turning cannot be prevented during rapid steering
Solution Approach 1:
The system applies preliminary action by narrowing the virtual steering range before excessive turning occurs. When the steering angle velocity exceeds the predetermined value, the virtual steering range is reduced in advance, preventing the turning angle from becoming excessively large. This proactive control approach is more effective than increasing reaction force after nonlinear characteristics have already developed.
3Reliability
If the virtual steering range is narrowed during rapid steering, then excessive turning is suppressed, but the steering feel may be affected
Solution Approach 1:
The virtual steering range is adjusted locally based on the steering angle velocity condition. During rapid steering maneuvers, the range is narrowed only in the high-velocity region, while maintaining the normal range during steady-state operation. This localized adjustment ensures turning control accuracy when needed without affecting the overall steering feel and responsiveness.
Data Source
AI summary
A reaction force actuator applies, during normal operation, a steering reaction force, which rapidly increases upon approaching an upper limit of a virtual steering range, to a steering wheel. During rapid steering in which a turning angle velocity is greater than or equal to a predetermined value and a turning follow delay is greater than or equal to a predetermined value, the reaction force actuator applies a steering reaction force to the steering wheel based on an upper limit corresponding to a narrower virtual steering range.