Steering Device Target Angle Correction for Axial Force Balance
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Solution Overview
Problem
Conventional steer-by-wire steering devices face difficulties in maintaining force balance between the turning force generated by the turning motor and the axial force on the turning shaft, especially when the axial force exceeds the maximal turning force, leading to uneven wheel turning and potential driver discomfort, particularly at vehicle stop or low speed states.
Innovation Solution
A steering device with a control system that adjusts the target angle to stay within a region where the force balance between the turning motor's maximal force and the axial force can be maintained, slowing the increase in target angle as it approaches the limit value, and optionally using restriction values to manage this balance, especially during vehicle stop or low speed conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the turning motor generates maximal turning force to overcome high axial force during stationary steering, then the turning wheels can be turned, but the force balance between turning force and axial force is disrupted, causing uneven wheel turning and driver discomfort
Solution Approach 1:
The control device dynamically adjusts the target angle based on vehicle speed and current angle, creating a speed-dependent control system that adapts to different operating conditions. At low speeds, the target angle is restricted to maintain force balance, while at higher speeds, full steering response is allowed.
Solution Approach 2:
The system changes the control parameter (target angle) based on vehicle speed conditions. By modifying the target angle calculation according to speed thresholds, the system maintains force balance at low speeds while preserving normal steering characteristics at higher speeds.
2Speed
If the target angle increases rapidly to match steering wheel input, then steering responsiveness is improved, but the turning wheels may not move smoothly when axial force exceeds maximal turning force
Solution Approach 1:
The control system dynamically adjusts the relationship between steering wheel input and target angle based on vehicle speed. At low speeds, the target angle increases more slowly to match the actual turning capability, while at higher speeds, the full steering response is provided.
Solution Approach 2:
The control device acts as an intermediary between the steering wheel input and the turning motor output. It mediates the steering command by calculating a corrected target angle that accounts for force balance limitations at low speeds, ensuring smooth wheel turning while maintaining steering responsiveness.
3Ease of operation
If the turning wheels are restricted to maintain force balance at low speeds, then smooth wheel turning is achieved, but the steering response may feel delayed or restricted to the driver
Solution Approach 1:
The control system dynamically adjusts the steering response characteristics based on vehicle speed. The restriction on target angle increase is applied only at low speeds where force balance is critical, while at higher speeds the full steering response is restored, preventing driver perception of delay.
Solution Approach 2:
The system changes the control parameter (target angle calculation) based on vehicle speed thresholds. By switching between different control modes (restricted at low speed, full response at high speed), the system maintains smooth wheel turning without creating perceivable steering delays for the driver.
Data Source
AI summary
A steering device includes a turning shaft, a turning motor, and a control device that controls the turning motor such that an angle capable of being converted into a turning angle of a turning wheel follows a target angle that is calculated depending on a steering state of a steering wheel. The control device executes a correction process of correcting the target angle. The control device corrects the target angle such that the degree of an increase in the target angle is slower as the target angle approaches a limit value of an angle region, when the target angle increases toward the limit value of the angle region in either of a vehicle stop state or an extremely low speed state.