Steer-by-Wire Fallback Control Using Braking and Drive Torque
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Solution Overview
Problem
Steer-by-wire systems in motor vehicles face challenges in achieving cost-effective and simple redundancy to ensure safe lateral control, particularly in the event of a steering system failure, as existing solutions are complex and expensive or insufficiently effective.
Innovation Solution
A safety system with a redundant main and safety level, including an emergency operating level that activates upon failure, using wheel-selective braking and drive torques to maintain vehicle stability, incorporating vehicle and chassis models for precise force calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simple redundancy is implemented in steer-by-wire systems, then the system meets basic safety requirements, but the vehicle must stop after a fault occurs
Solution Approach 1:
The control unit is segmented into multiple independent operating levels (main operating level, safety level, emergency operating level), each capable of independently controlling the steering actuator. This segmentation allows the system to maintain functionality even when some levels fail, enabling continuous vehicle operation after faults.
Solution Approach 2:
The system dynamically switches between different operating levels based on fault detection. The control unit monitors the status of each level and automatically transitions to a backup level when a failure is detected, maintaining continuous steering control without requiring vehicle stoppage.
2Reliability
If double redundancy with triple-redundant control unit or triple windings is implemented, then the vehicle can continue driving after fault, but the system becomes very complex and expensive
Solution Approach 1:
Multiple operating levels are merged within a single control unit rather than using separate redundant control units. The main operating level, safety level, and emergency operating level coexist in one control unit, sharing common hardware resources while providing multiple layers of redundancy. This reduces overall system complexity and cost.
Solution Approach 2:
The control unit is designed with multi-functionality, where a single control unit performs the functions of multiple redundant control units through its different operating levels. Each level can independently execute steering control, making the control unit universal and eliminating the need for multiple dedicated redundant units.
Data Source
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AI summary
The invention relates to a safety system (2) for vehicle lateral control for a steer-by-wire steering system of a motor vehicle (1), comprising a main operating level (3) for transmitting a steering wheel angle to at least one wheel (5) of the motor vehicle (1), and a safety level (4) for transmitting a steering wheel angle to at least one wheel (5) of the motor vehicle (1), wherein the safety level (4) is configured to become active in the event of a failure of the main operating level (3). It is proposed that an emergency operating level (6) for vehicle lateral control be provided, wherein the emergency operating level (6) is configured to become active in the event of a failure of the main operating level (3) and/or the safety level (4).