Steer-by-Wire Lateral Control Fallback Using Emergency Braking
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Solution Overview
Problem
Steer-by-Wire steering systems in motor vehicles face challenges in achieving cost-effective double redundancy for safety and availability, leading to potential vehicle stall in the event of a fault, necessitating a low-cost and simple fallback level for continued vehicle operation.
Innovation Solution
A redundant safety system with a main operating level, safety level, and emergency operating level is implemented, where the emergency level activates upon failure of the main or safety level, using an emergency control unit to calculate wheel-specific braking and driving forces for vehicle lateral control, integrating with existing systems and models to ensure stable vehicle operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simple redundancy is implemented in Steer-by-Wire system, then safety requirement is met, but vehicle must be stopped after fault leading to hard stall
Solution Approach 1:
The patent implements a three-level redundancy architecture where an emergency operating level is pre-configured as a fallback mechanism. When the main operating level fails, the safety level takes over, and if that fails, the emergency level with its simplified control unit and basic steering functions activates to prevent hard stall. This beforehand cushioning ensures continuous vehicle operation even after multiple failures.
2Reliability
If double redundancy is implemented by keeping additional technology on hand, then vehicle can continue to drive after fault, but system becomes very time-consuming and cost-intensive
Solution Approach 1:
The patent segments the redundancy system into three distinct levels with progressively simplified functions. The main operating level handles full steering functions, the safety level provides intermediate backup, and the emergency operating level provides basic steering capability. This segmentation allows each level to be optimized for its specific purpose, reducing overall system complexity compared to maintaining full functionality at all levels.
Solution Approach 2:
The emergency control unit in the emergency operating level is designed with local quality - it has simplified steering control capabilities appropriate for emergency situations rather than full steering functionality. This localized optimization of functionality reduces the complexity and cost of the emergency level while maintaining sufficient capability for safe vehicle operation during critical failures.
3Reliability
If triple control unit or motor with triple windings is used for double redundancy, then safety is enhanced, but implementation becomes very time-consuming and cost-intensive
Solution Approach 1:
The patent achieves double redundancy through a multi-functional architecture where the emergency control unit can serve multiple purposes: it acts as a backup steering controller, provides basic vehicle stability control, and enables limited maneuvering capability. This universality reduces the need for completely separate triple control units, simplifying manufacturing while maintaining reliability.
Data Source
AI summary
A safety system for vehicle lateral control for a Steer-by-Wire steering system of a motor vehicle with a main operating level for transmitting a steering wheel angle to at least one wheel of the motor vehicle, and with a Safety level for transmitting a steering wheel angle to at least one wheel of the motor vehicle. The safety level may be configured to become active if the main operating level fails. An emergency operating level is provided for vehicle lateral control, the emergency operating level being arranged to become active in the event of a failure of the main operating level and/or safety level.