Steering Control Device Switching Clutch for Angle Conformity
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Solution Overview
Problem
In steer-by-wire systems, excessive loads or high temperatures can cause discrepancies between steering angles and turning angles, leading to inadequate reaction forces and torque, resulting in non-conformity between these angles.
Innovation Solution
A steering control device that includes a controller to switch the switching device from a cutoff state to a transmission state when the difference between the controlled variable and the command value exceeds a threshold, ensuring torque is applied to the steered wheels and assisting in turning through cooperation of user input and actuator forces, while also managing temperatures to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If current in the turning-side actuator is limited to prevent overheating, then temperature control is improved, but torque becomes insufficient and turning angle does not conform to steering angle
Solution Approach 1:
The clutch serves as an intermediary mechanical connection between the steering wheel and steered wheels. When the turning-side actuator cannot provide sufficient torque due to current limiting, the clutch engages to transmit torque from the steering wheel to the steered wheels, ensuring turning angle conformity is maintained even under thermal constraints
Solution Approach 2:
The system dynamically switches between cutoff state (relying on turning-side actuator) and transmission state (relying on mechanical connection via clutch) based on real-time monitoring of turning angle deviations. When deviation exceeds threshold, the system transitions to transmission state to ensure conformity, then returns to cutoff state when conformity is restored
2Temperature
If current in the steering-side actuator is limited to prevent overheating, then temperature control is improved, but maximum reaction force is reduced and steering angle becomes excessively large
Solution Approach 1:
The clutch acts as a mechanical intermediary that directly connects the steering wheel to the steered wheels, bypassing the need for steering-side actuator current to generate reaction force. This mechanical connection ensures steering angle conformity is maintained while the actuator current is limited for temperature control
Solution Approach 2:
The system replaces the electrical-mechanical conversion path (steering-side actuator converting electrical current to reaction force) with a direct mechanical transmission path through the clutch. This substitution eliminates the need for high current in the steering-side actuator while maintaining steering angle conformity
3Ease of operation
If the switching device remains in cutoff state to use turning-side actuator for precise control, then steering reaction force control is improved, but under excessive load the turning angle cannot conform to steering angle
Solution Approach 1:
The system dynamically transitions between cutoff state and transmission state based on load conditions and turning angle conformity. In normal conditions, cutoff state provides precise control. Under excessive load, the system switches to transmission state where the mechanical connection ensures conformity, then returns to cutoff state when conditions improve
Data Source
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AI summary
A steering control device includes a controller configured to execute turning processing of controlling a controlled variable to a command value corresponding to an operation of a steering wheel (12) by controlling a turning-side actuator (40) in a cutoff state, the controlled variable being at least one of a turning angle of the steered wheels (30) and a turning angle rate that is a changing rate of the turning angle; and transmission switching processing of controlling a switching device (14, 66) such that the switching device (14, 66) is switched from the cutoff state to a transmission state on condition that an absolute value of a difference between the controlled variable and the command value continues to be equal to or larger than a threshold when the turning processing is executed.