Rear-Wheel Backup Steering for Steer-by-Wire Failure Control
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Solution Overview
Problem
The steering-by-wire (SBW) system in vehicles loses its steering function when an abnormality such as a wire defect occurs, and implementing redundancy to maintain fail-safe capabilities increases manufacturing costs.
Innovation Solution
A steering apparatus that utilizes a rear wheel steering system to provide backup redundancy, applying braking and driving forces to the front and rear wheels to assist in steering when an abnormality occurs in the SBW system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If duplexing RWA and SFA is implemented to provide steering redundancy, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The rear wheel steering system is designed to perform dual functions: normal steering assistance and emergency backup steering. When the SBW system is abnormal, the rear wheel steering system takes over to provide steering redundancy, eliminating the need for separate duplexed RWA and SFA components.
Solution Approach 2:
The rear wheel steering system acts as an intermediary backup mechanism between the primary SBW system and the driver. When the SBW system fails, the rear wheel steering system mediates by providing alternative steering capability through coordinated braking and driving forces.
2Ease of manufacture
If rear wheel steering system is used for backup redundancy, then manufacturing cost is reduced, but steering control complexity increases
Solution Approach 1:
The control system continuously monitors the steering state and SBW system status, providing feedback to determine when to switch to rear wheel steering mode. The controller adjusts braking and driving forces based on feedback from steering angle sensors and system status to maintain stable steering control.
Solution Approach 2:
The system dynamically switches between normal SBW operation and rear wheel steering backup mode based on real-time system status. The rear wheel steering system adjusts its operation dynamically by varying braking and driving forces to match driver intent and vehicle state.
3Reliability
If braking force and driving force are applied to front and rear wheels for steering assistance, then steering functionality is maintained, but energy consumption increases
Solution Approach 1:
The rear wheel steering system operates periodically or intermittently based on system needs rather than continuously. It activates only when SBW system abnormality is detected and deactivates when normal operation is restored, reducing unnecessary energy consumption while maintaining steering functionality when needed.
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
Enables the vehicle to maintain steering functionality through the rear wheel steering system during abnormalities in the SBW system, thereby ensuring vehicle safety and reducing manufacturing costs associated with redundancy.
Implementation Method 1
a first control step of applying a braking force to a first front wheel and a second front wheel disposed on a front side of the vehicle
Implementation Method 2
applying a driving force to a first rear wheel and a second rear wheel disposed on the rear side of the vehicle
Data Source
AI summary
A method for controlling a vehicle including a steering-by-wire (SBW) system includes determining whether an abnormality has occurred in the SBW system; in response to determining an abnormality has occurred at the SBW system, operating a rear wheel steering system; applying a braking force to a first front wheel and a second front wheel disposed on a front side of the vehicle and applying a driving force to a first rear wheel and a second rear wheel disposed on the rear side of the vehicle; and in response to determining a turning radius of the vehicle by the rear wheel steering system does not satisfy a required turning radius input to a steering wheel, applying an additional braking force to the first front wheel and the second front wheel.