Rear Wheel Steering Control via Sensor Error Detection
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Solution Overview
Problem
Conventional rear wheel steering systems experience unstable control due to sudden changes in steering amounts caused by errors in wheel speed sensors, particularly during rapid braking or acceleration, leading to inaccurate vehicle speed estimation and potential differences in rear wheel control.
Innovation Solution
A control method that detects errors in wheel speed sensors and estimates vehicle speed using normal sensors, replacing abnormal sensor values with averages from diagonally positioned or remaining normal sensors, and adjusts steering based on these estimates to prevent sudden changes in rear wheel steering control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If wheel speed sensor values are used directly for vehicle speed estimation, then the system responds quickly to speed changes, but sensor errors cause sudden changes in rear wheel steering control amount
Solution Approach 1:
The patent introduces an intermediary processing mechanism between the wheel speed sensors and the vehicle speed estimation. When a sensor error is detected (wheel acceleration exceeds threshold), the system uses diagonal sensor values as intermediate data to calculate average wheel speed, preventing direct transmission of erroneous values to the control system while maintaining quick response to legitimate speed changes.
Solution Approach 2:
The system implements feedback by continuously monitoring wheel acceleration to detect sensor errors. When abnormal acceleration is detected, the feedback mechanism triggers an alternative calculation method using diagonal sensor values, and after a predetermined time without abnormal acceleration, the system feedback-diagnoses the sensor as normal again, creating a self-correcting control loop.
2Measurement precision
If average value of all four wheel speed sensors is used for vehicle speed estimation, then the estimation is comprehensive, but abnormal sensor values cause inaccurate vehicle speed estimation
Solution Approach 1:
The patent applies local quality by treating different sensor positions differently based on their reliability. When a sensor error is detected, the system selectively excludes only the abnormal sensor's diagonal position from the average calculation, while still using the other three sensors. This localized adjustment maintains measurement precision by excluding only the problematic data point rather than reducing overall sensor utilization.
Solution Approach 2:
The system changes the calculation parameters dynamically based on sensor performance. Under normal conditions, all four sensors are used with equal weight. When a sensor error is detected, the parameter change switches to using only three sensors (excluding the abnormal one and its diagonal counterpart), and the weighting parameters are adjusted accordingly to maintain accurate vehicle speed estimation despite the reduced sensor input.
3Productivity
If rapid braking or acceleration occurs, then vehicle dynamics change quickly, but wheel speed sensor errors cause sudden vehicle speed estimation changes
Solution Approach 1:
The system performs preliminary error detection by monitoring wheel acceleration before the erroneous sensor value can significantly affect vehicle speed estimation. By detecting abnormal acceleration patterns in advance, the system proactively switches to the alternative calculation method using diagonal sensor values, preventing the propagation of errors during rapid maneuvers rather than reacting after errors occur.
Data Source
AI summary
A control method of a rear wheel steering system prevents a sudden change in a rear wheel steering control amount when an error occurs in a wheel speed sensor. The control method detects an error in wheel speed sensors based on output values of the wheel speed sensors. A vehicle speed is estimated by using output values of remaining normal wheel speed sensors except for an output value of an abnormal wheel speed sensor where an error is detected, when an error in the wheel speed sensor is detected. Rear wheels are steered and controlled based on the estimated vehicle speed.