Steering Reaction Torque Control for Steer-by-Wire End Contact
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Solution Overview
Problem
Conventional steer-by-wire systems lack an effective method to provide a comfortable contact feeling to drivers when the steering wheel reaches its turning limit, often requiring a large steering reaction actuator to generate a maximum reaction force, which can be uncomfortable and inefficient.
Innovation Solution
A steering controller that includes a direction varying torque control means and a steering reaction control means, using a backup clutch to gradually increase the steering reaction torque over time as the steering wheel approaches its maximum angle, allowing a small-sized steering reaction actuator to provide an excellent end contact feeling by simulating mechanical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum reaction force is abruptly generated by the steering reaction actuator when deviation is greater than or equal to a predetermined value, then the steering wheel can be stopped at the turning limit, but the driver experiences an uncomfortable contact feeling
Solution Approach 1:
The patent applies beforehand cushioning by gradually increasing the reaction force before the steering wheel reaches the hard stop. The control device increases the reaction force in stages as the steering wheel approaches the turning limit, rather than abruptly applying maximum force. This gradual increase cushions the transition and provides the driver with a more comfortable contact feeling while still ensuring the steering wheel stops at the correct position.
2Reliability
If a large steering reaction actuator is used to generate maximum reaction force, then the steering wheel can be effectively controlled at the turning limit, but the space and cost requirements increase
Solution Approach 1:
The patent applies dynamics by making the reaction force variable rather than constant. The control device dynamically adjusts the reaction force based on the steering wheel's position and deviation from the target angle. By using a smaller actuator that can generate varying reaction forces (from small incremental forces to larger corrective forces), the system achieves effective steering control without requiring a large, heavy actuator capable of generating maximum force continuously.
Solution Approach 2:
The patent applies parameter changes by varying the reaction force parameter according to the steering state. The control device changes the reaction force parameter in stages: applying small reaction forces when the steering wheel is approaching the limit, increasing to medium forces at intermediate deviations, and using maximum forces only when necessary to correct large deviations. This parameter variation allows a smaller actuator to achieve the same control effect as a larger actuator operating at constant maximum force.
Data Source
AI summary
A steering control apparatus is provided, including a steering wheel, steered wheels, a direction varying actuator to operate the steering control wheels, a steering reaction actuator to apply steering reaction torque to the steering wheel and steering controller. The steered wheels are mechanically disconnected from the steering wheel. The steering controller outputs control commands for controlling the direction varying actuator and the steering reaction actuator.