Steer-by-Wire Fallback Architecture for Residual Steerability
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Solution Overview
Problem
Existing steer-by-wire systems fail to effectively address the challenge of maintaining residual steerability in the event of multiple component failures, particularly in the steering unit, leading to a loss of steerability and a loss of steering control.
Innovation Solution
The steer-by-wire steering system incorporates redundant components such as steering wheel angle sensors and redundant steering angle processors, coupled in communication, with redundant rack actuators and actuator processors, to maintain steerability even in the event of multiple component failures by utilizing an electronic fallback system that includes a rear axle steering system and/or an electronic stability system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant components are provided within the steering unit for internal fault compensation, then reliability against singular failures is improved, but device complexity increases
Solution Approach 1:
The steering unit is segmented into functionally independent redundant subsystems (steering angle processors, rack actuators, communication lines) that can operate autonomously. Each subsystem can take over when another fails, maintaining overall steerability while keeping individual component complexity manageable.
Solution Approach 2:
Redundancy is implemented locally at critical components (steering angle processors, rack actuators, communication lines) rather than throughout the entire system. This targeted approach provides necessary fault tolerance at failure-prone points while avoiding unnecessary complexity in less critical areas.
2Reliability
If an electronic fallback system is provided outside the steering unit, then residual steerability is maintained in case of multiple failures, but device complexity and signal transmission requirements increase
Solution Approach 1:
An electronic fallback system acts as an intermediary between the steering unit and the vehicle's existing electronic systems (braking system, rear axle steering system, electronic stability system). This mediator enables signal transmission and coordination between systems, allowing residual steerability to be maintained through cooperative control when the primary steering unit fails.
Solution Approach 2:
The fallback system leverages existing multi-functional electronic systems already present in the vehicle (braking system, rear axle steering system, electronic stability system). These systems serve their primary functions while also being capable of providing steering assistance when needed, avoiding the need for dedicated single-function backup components.
3Reliability
If communication lines are provided between each steering angle processor and actuator processor for internal compensation, then steerability is maintained without restriction during singular faults, but loss of information increases when multiple failures occur
Solution Approach 1:
The system implements feedback mechanisms where the electronic fallback system continuously monitors the status of communication lines and processor functionality. When communication failures are detected, the fallback system adjusts signal transmission paths and activates alternative communication routes through existing vehicle electronic systems, ensuring steering control information is maintained.
Data Source
AI summary
A steer-by-wire steering system for a vehicle is indicated, having a steering unit which has a steering wheel angle detection unit for detecting a steering wheel angle adjusted on a steering wheel by a driver and a rack-and-pinion unit for adjusting a steering angle on a vehicle axle, for example a vehicle front axle, wherein the steering wheel angle detection unit is configured to translate the steering wheel angle adjusted by the driver into a steering angle request and to pass the steering angle request on to the rack-and-pinion unit, which is configured to adjust an axial position of a rack in accordance with the steering angle request. The steering system further has at least one electronic system which is provided outside the steering unit and coupled to the steering unit via electronic lines in terms of signaling, wherein the at least one electronic system is an electronic fallback system and, together with the steering unit, constitutes an emergency steering functional system. Furthermore, a method of steering a vehicle by means of a steer-by-wire steering system is indicated.