Steering Backup Control Using Rear-Wheel Steering and Differential Braking
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Solution Overview
Problem
The steer-by-wire (SbW) system in vehicles faces challenges in achieving target steering due to communication failures, compromising safety and stability, especially in autonomous driving scenarios.
Innovation Solution
A steering control device and method that integrates differential braking and rear wheel steering to maintain target steering direction by determining a target yaw rate based on sensor information and generating control signals for differential braking and rear wheel steering, compensating for potential failures in the SbW system without additional mechanical designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a steer-by-wire (SbW) system is used to reduce steering force and ensure stability, then steering stability is improved, but communication failures may occur causing loss of target steering control
Solution Approach 1:
The patent implements a backup steering control mechanism that is activated beforehand when SbW system failure is detected. The controller monitors SbW system status and automatically switches to alternative control methods (differential braking or rear wheel steering) to cushion against the potential loss of target steering control, ensuring continuous steering capability even when communication failures occur.
2Reliability
If differential braking is used for steering control during SbW failure, then target steering can be achieved, but negative scrub radius effects compromise vehicle stability
Solution Approach 1:
The patent introduces rear wheel steering as an intermediary mechanism to mediate between differential braking and vehicle stability. When differential braking is activated for target steering during SbW failure, the rear wheel steering system works in coordination to counteract the negative scrub radius effects, thereby maintaining vehicle stability while achieving the desired steering direction.
Solution Approach 2:
The patent dynamically changes steering control parameters by switching between different control modes (normal SbW control, differential braking, rear wheel steering) based on system failure detection. The controller adjusts steering angle, braking force distribution, and rear wheel steering angle parameters to optimize both target steering achievement and vehicle stability under failure conditions.
3Reliability
If additional mechanical designs are added to provide redundancy for SbW failure, then steering safety is improved, but device complexity increases
Solution Approach 1:
The patent makes existing mechanical components multi-functional to provide redundancy without adding new mechanical systems. The braking system, originally designed for deceleration, is made capable of differential braking for steering control. The rear wheel steering system, originally for stability enhancement, is made capable of compensating for negative scrub radius effects during failure-mode steering. This universal usage of existing components provides steering safety redundancy while avoiding additional mechanical complexity.
Data Source
AI summary
The embodiments may provide a steering control device of a vehicle equipped with a steer-by-wire steering system and a rear wheel steering system. A steering control device may include a sensor configured to acquire information on the vehicle, and a controller configured to, in response to a determination of a failure of the steer-by-wire steering system, determine a target yaw rate according to a target steering angle based on the information acquired from the sensor, and generate and output a differential braking control signal and a rear wheel steering control signal to follow the target yaw rate.