Steer-by-wire redundancy via asymmetric fallback adjusting device
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Solution Overview
Problem
Steer-by-wire steering systems lack effective redundancy for reaction force and rack position adjustment, leading to increased costs due to the need for functionally identical communication connections for redundant components.
Innovation Solution
A dual-channel system with a primary and fallback adjustment device, where the primary device is designed for normal operation and the fallback device is cost-effectively designed for emergency use, utilizing different microprocessors and communication connections to provide redundant reaction force and rack position adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant components are included to provide safety, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies local quality by designing the primary and fallback adjusting devices with different functional capabilities. The primary device has full functionality for normal operation, while the fallback device has reduced functionality activated only during faults. This asymmetric design provides redundancy where needed (improving reliability) while avoiding unnecessary complexity in the fallback path.
Solution Approach 2:
The fallback adjusting device is designed as a simpler, more cost-effective solution intended for temporary emergency operation. It uses fewer communication connections and less powerful components, accepting that it is a temporary measure until the primary device is restored or the vehicle is serviced.
2Reliability
If functionally identical communication links are provided for redundant components, then reliability is improved, but cost increases
Solution Approach 1:
The fallback adjusting device utilizes existing vehicle bus communication infrastructure rather than requiring dedicated redundant communication links. This multi-functionality approach allows the same communication bus to serve both normal and fallback operations, eliminating the need for separate identical communication paths and reducing overall system cost.
Solution Approach 2:
The fallback device creates a simplified copy of the primary device's functionality, using the same communication bus for control signals. Instead of duplicating all communication infrastructure, it leverages the existing bus system, providing redundancy at lower cost by copying only the essential control functions.
Data Source
Figure 1~2
AI summary
The invention relates to a steer-by-wire steering system (1) for a motor vehicle, comprising: a steering handle (2) which can be actuated by a driver; a vehicle wheel actuator (11), which is configured to adjust a wheel steering angle of at least one steerable wheel of the vehicle; a reaction force actuator (5) which is connected to the steering handle (2) and is configured to produce a reaction force acting against a deflection of the steering handle (2); a primary adjusting device (12), which is configured to adjust the reaction force produced by the reaction force actuator (5), and a fallback adjusting device (14), which is configured to adjust the reaction force produced by the reaction force actuator (5) in the event of a malfunction of the primary adjusting device (12); the primary adjusting device (12) being further configured to output a manipulated variable (S) for adjusting the wheel steering angle, and the fallback adjusting device (14) being further configured to output a manipulated variable (S`) for adjusting the wheel steering angle in the event of a malfunction of the primary adjusting device (12); and the fallback adjusting device (14) and the primary adjusting device (12) being designed differently from one another. The invention further relates to a method for operating a steer-by-wire steering system (1) for a motor vehicle.