Steer-by-wire friction suppression for smooth automatic steering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In vehicles with steer-by-wire steering mechanisms, automatic steering control is hindered by fluctuations in the steering angle due to the steering reaction force generated by the actuator, leading to unstable and non-smooth steering.
Innovation Solution
A steering control method that includes a restoration component, a viscous component, and a friction component to generate a steering reaction force, with an actuator controlling the steering wheel to maintain a target steering angle and suppress the friction component during automatic steering, ensuring smooth operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a steering reaction force including friction component is applied to the steering wheel during automatic steering control, then steering feel is improved, but steering angle fluctuations occur and smooth steering is hindered
Solution Approach 1:
The friction component suppression determination unit dynamically adjusts the friction component based on the operating state. When automatic steering control is determined to be operating, the friction component is suppressed (set to zero or reduced). When manual operation is detected, the friction component is restored to provide natural steering feel. This dynamic adjustment resolves the contradiction by adapting the friction characteristic to the current control mode.
Solution Approach 2:
The patent changes the parameter of friction component in the steering reaction force based on the control mode. By detecting whether the system is in automatic steering control mode or manual operation mode, the friction component parameter is modified accordingly - suppressed during automatic control to prevent fluctuations, and restored during manual operation to maintain steering feel.
2Reliability
If friction component is included in steering reaction force during automatic steering, then steering reaction force is complete, but steering angle fluctuates and smooth control is hindered
Solution Approach 1:
The system dynamically switches the friction component based on control mode detection. During automatic steering control, the friction component is suppressed to ensure smooth and precise control. During manual operation, the friction component is restored to provide complete steering reaction force. This dynamic behavior resolves the contradiction between completeness and smoothness.
Solution Approach 2:
The friction component is extracted or removed from the steering reaction force calculation when automatic steering control is detected. The friction component suppression determination unit identifies when automatic control is active and excludes the friction component from the reaction force, preventing fluctuations while maintaining other necessary components of the steering force.
3Manufacturing precision
If actuator applies rotational torque to steering wheel for automatic steering control, then steered wheels are controlled accurately, but steering angle fluctuations occur due to steering reaction force
Solution Approach 1:
The friction component parameter in the steering reaction force is changed based on control mode. During automatic steering control, the friction component is suppressed to prevent fluctuations that would interfere with precise control. The actuator can then apply rotational torque accurately without causing steering angle fluctuations from friction variations.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In a steering control method for a vehicle, equipped with a steer-by-wire steering mechanism in which the steering wheel (31a) and the steered wheels (34FL, 34FR) are mechanically separated, a steering reaction force including a restoration component for restoring a steering angle of the steering wheel to a reference angle, a viscous component corresponding to a steering angular velocity of the steering wheel, and a friction component corresponding to the steering angular velocity, is generated by an actuator and applied (S9) to the steering wheel, a steering reaction force is controlled (S1, S5) such that the steering angle becomes a target steering angle for causing the vehicle to travel along a target travel path, the turning angle of the steered wheels is controlled (S11) in accordance with the steering angle, it is determined (S2) whether a driver has operated the steering wheel, and the friction component included in the steering reaction force is suppressed (S6-S9) when the driver does not operate the steering wheel.