Steer-by-Wire Clutch Engagement Control via Angular Acceleration
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Solution Overview
Problem
In steer-by-wire steering systems, rapid changes in steering wheel angle can lead to erroneous engagement of the clutch, causing unintended torque application to the steering wheel and driver discomfort due to increased relative angular acceleration between the steering and turning angles.
Innovation Solution
A vehicle steering device with a selectively engageable clutch and reaction force actuator that controls the turning actuator to reduce relative angular acceleration, preventing erroneous clutch engagement by adjusting the turning angle and applying a steering reaction force to match the driver's input, thus maintaining normal steer-by-wire control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clutch is designed to engage during rapid steering changes to provide mechanical backup, then reliability is improved, but driver discomfort increases due to unintended torque application
Solution Approach 1:
The control device predicts the clutch engagement state in advance by detecting steering angle acceleration and comparing it with predetermined thresholds before actual engagement occurs. This preliminary detection allows the system to prepare appropriate reaction forces to prevent driver discomfort when engagement does occur.
Solution Approach 2:
The control device continuously monitors steering angle acceleration and uses this feedback to dynamically adjust the reaction force actuator output. By comparing detected acceleration with threshold values, the system provides real-time feedback control to maintain reliable clutch engagement while minimizing harmful torque applications to the driver.
2Reliability
If the clutch engages during rapid steering changes, then mechanical backup control is activated, but the steering reaction force becomes unnatural causing driver discomfort
Solution Approach 1:
The system predicts clutch engagement states in advance by monitoring steering angle acceleration thresholds before actual engagement occurs. This allows the control device to pre-adjust the reaction force actuator to maintain natural steering feel during the transition to mechanical backup control.
Solution Approach 2:
The control device dynamically changes the reaction force parameter based on detected steering acceleration and predicted clutch engagement states. By adjusting the reaction force magnitude and timing according to acceleration thresholds, the system maintains natural steering characteristics during mechanical backup operation.
3Reliability
If the reaction force actuator applies strong forces to prevent clutch engagement, then erroneous engagement is reduced, but steering responsiveness deteriorates
Solution Approach 1:
The control device applies reaction force only when steering angle acceleration exceeds predetermined thresholds, rather than continuously. This partial action approach prevents erroneous clutch engagement during normal rapid steering maneuvers while maintaining steering responsiveness during ordinary operation.
Solution Approach 2:
The system dynamically adjusts the reaction force parameter based on steering acceleration conditions. By changing the reaction force magnitude only when acceleration exceeds thresholds, the system maintains high steering responsiveness during normal operation while preventing erroneous clutch engagement during abnormal rapid changes.
Data Source
AI summary
In a vehicle steering device and control method, a selectively engageable clutch is positioned between a steering wheel and a turning mechanism for turning at least one wheel. The clutch has an engaged position where the steering wheel is mechanically connected to the turning mechanism and a disengaged position where the steering wheel is mechanically separated from the turning mechanism for steer-by-wire control. During steer-by-wire control, a reaction force actuator applies a force to the steering wheel, and a turning actuator applies a torque to the turning mechanism. To prevent erroneous clutch engagement caused by an increase in relative angular acceleration between the steering angle and the turning angle, a controller detects an operating condition corresponding to a risk of erroneous clutch engagement and controls at least one of the turning actuator and the reaction force actuator to reduce the relative angular acceleration.