Steering System Torque Distribution for Fault Tolerance
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Solution Overview
Problem
Existing electromechanical power steering systems lack sufficient fault tolerance, which can lead to system failures and reduce their reliability for autonomous driving applications where direct driver intervention is not guaranteed.
Innovation Solution
A method and system that determine and distribute partial assist torques across multiple actuator paths, allowing for redundancy and automatic role switching between master and slave paths, ensuring continuous operation even with component faults or reduced capacity, thereby enhancing the overall availability of the steering system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant actuator paths are implemented in the steering system, then the fault tolerance and reliability are improved, but the device complexity increases
Solution Approach 1:
The steering system is divided into multiple independent actuator paths (first actuator path and second actuator path), each capable of independently determining partial assist torques. This segmentation allows the system to isolate faults to specific paths while maintaining operational capability through remaining paths, thereby improving fault tolerance without requiring complete system redundancy.
Solution Approach 2:
Multiple actuator paths are merged into a unified control system where partial assist torques from different paths are combined to form the total assist torque. The control unit integrates signals from multiple sensors and actuators, coordinating their operation to achieve the desired steering assistance while managing complexity through centralized control.
2Reliability
If centralization of partial assist torque determination is implemented, then the fault tolerance is improved, but the calculation complexity increases
Solution Approach 1:
The control unit is pre-programmed with the methodology for determining partial assist torques in each actuator path. The calculation framework is established in advance, including the logic for fault detection and the procedures for switching between actuator paths. This preliminary preparation enables rapid response to faults without requiring complex real-time decision-making algorithms.
Solution Approach 2:
The system continuously monitors the operational status of each actuator path and uses this feedback to determine whether centralization of torque calculation is necessary. When faults are detected, the feedback mechanism triggers appropriate responses such as switching to alternative paths or adjusting torque distribution, thereby managing calculation complexity through condition-based activation rather than continuous complex computation.
3Reliability
If automatic role switching between master and slave actuator paths is implemented, then the availability is improved, but the control complexity increases
Solution Approach 1:
The roles of actuator paths are made dynamic rather than fixed. The control unit can switch between actuator paths based on real-time fault conditions, allowing the system to adapt its configuration dynamically. This dynamic role assignment improves availability by ensuring continuous operation even when specific paths fail, while the switching logic is designed to be straightforward based on fault detection results.
Data Source
AI summary
A method for operating a steering system of a motor vehicle with a power steering system including a number of actuator paths for applying a total assist torque to a steering gearbox includes determining the total assist torque in each of the actuator paths. The method further includes determining partial assist torques for all actuator paths in each of the actuator paths. The method further includes receiving the associated partial assist torque by each of the actuator paths from the actuator path that is activated as a master.