Steering System Clutch Engagement Control via Reactive Torque
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Solution Overview
Problem
Existing steer-by-wire vehicle steering systems engage the clutch frequently, leading to increased operating noise and reduced durability, and fail to maintain the correspondence between the steering wheel and steered wheels' angles, especially when higher steering torques are applied.
Innovation Solution
A vehicle steering system that includes a steering member, a steering operation mechanism, a clutch, a reactive-torque motor, and a clutch engagement controller, where the clutch is engaged only when the steered wheels have reached a steered angle limit and the steering member is rotated by a prescribed value against the reactive-torque applied by the reactive-torque motor, reducing unnecessary clutch engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clutch is engaged each time the rack shaft reaches the movable end to suppress steering wheel rotation, then the steering angle correspondence is maintained, but the frequency of clutch engagement increases, generating operating noise and reducing clutch durability
Solution Approach 1:
The reactive-torque motor applies a stopping torque to the steering wheel before the rack shaft reaches the movable end, preventing the steering wheel from rotating further. This preliminary action avoids the need for clutch engagement at the limit position, thereby reducing clutch wear and extending its service life while maintaining accurate steering angle correspondence.
2Reliability
If the clutch is engaged each time the rack shaft reaches the movable end, then the steering wheel rotation is suppressed, but the operating noise of the clutch increases
Solution Approach 1:
The reactive-torque motor applies a stopping torque to the steering wheel before the rack shaft reaches the movable end, preventing the steering wheel from rotating further. This preliminary action avoids the need for clutch engagement at the limit position, thereby reducing clutch wear and extending its service life while maintaining accurate steering angle correspondence.
3Duration of action of stationary object
If a reactive-torque motor is used to stop steering wheel rotation without engaging the clutch, then clutch durability is improved, but when high steering torque is applied the steering wheel rotates beyond the steered wheels, losing angle correspondence
Solution Approach 1:
The system dynamically switches between two control modes: normally, the reactive-torque motor controls the steering wheel angle; when the steered wheels reach their limit position, the clutch is engaged to mechanically connect the steering wheel and steered wheels. This dynamic switching ensures both clutch durability and accurate angle correspondence under all operating conditions.
Solution Approach 2:
The clutch serves as an intermediary mechanical connection that engages only when necessary (at the steered wheel limit position) to transfer torque from the steering wheel to the steered wheels. This intermediary role allows the system to maintain angle correspondence during high-torque situations without requiring continuous clutch engagement, thereby preserving clutch durability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration decreases the frequency of clutch engagement, reduces operating noise, and enhances clutch durability by ensuring accurate correspondence between the steering wheel and steered wheels' angles.
Implementation Method 1
The reactive-torque motor is configured to apply a steering reactive torque to the steering member
Implementation Method 2
The steering operation motor is configured to steer the steered wheels
Data Source
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AI summary
A vehicle steering system (1) includes a clutch (6) provided on a power transmission path extending from a steering wheel (2) to steered wheels (3), a reactive-torque motor (14) configured to apply a steering reactive torque to the steering wheel (2), a steering operation motor (31) configured to steer the steered wheels (3), and a clutch engagement controller (40) configured to engage the clutch (6) when a steered angle of the steered wheels (3) has reached a steered angle limit value and the steering wheel (2) is rotated by an amount equal to or greater than a first prescribed value (α) in a direction opposite to a direction toward a steering neutral position, with respect to a first steering angle that is a steering angle of the steering wheel (2) at a time when the steered angle reaches the steered angle limit value, in a case where the clutch (6) is in a disengaged state.