Vehicle Steering Arbitration Logic for Torque Limiting
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Solution Overview
Problem
Existing steering systems face challenges in reconciling simultaneous requests from multiple subsystems, leading to uncomfortable steering behavior and potential loss of control, due to inadequate arbitration and limitation of steering torque and angle, especially when systems activate simultaneously.
Innovation Solution
A device with arbitration and limitation logic that prioritizes steering requests based on vehicle state and driving style, ensuring the overall steering torque does not exceed predefined limits, implemented within an electronic control unit to manage multiple subsystems and maintain driver controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple steering subsystems operate simultaneously with independent control loops, then functional versatility and steering capabilities are improved, but system complexity and control arbitration difficulty increase
Solution Approach 1:
The control system is segmented into independent subsystems (EPAS, AFS, steer-by-wire) each with its own control loop, allowing them to operate autonomously while maintaining functional versatility. The arbitration logic is further segmented into priority evaluation, coincidence detection, and limitation stages, making the complex control arbitration manageable and modular.
Solution Approach 2:
An intermediary arbitration and limitation logic is introduced between the multiple steering subsystems and the final steering output. This mediator evaluates priorities, detects coinciding requests, and limits overall steering torque/angle, resolving conflicts without requiring complete reconfiguration of the entire control system.
2Speed
If steering requests from multiple subsystems are summed without arbitration, then responsiveness to various driving situations is improved, but driver controllability and safety deteriorate due to excessive steering torque
Solution Approach 1:
The arbitration and limitation logic performs preliminary evaluation of steering requests before they are executed. By detecting coinciding requests and evaluating priorities in advance, the system prevents excessive steering torque from being applied to the driver, ensuring safety while maintaining responsiveness.
Solution Approach 2:
The system continuously monitors steering requests from multiple subsystems and applies feedback through the arbitration logic. When coinciding requests are detected, the limitation logic adjusts the overall steering torque/angle to prevent exceeding safe limits, maintaining driver controllability while preserving system responsiveness.
3Ease of operation
If a central MIMO controller is used to manage multiple steering loops, then coordinated control of steering position and torque is improved, but adjustment complexity and robustness deteriorate
Solution Approach 1:
Instead of using a monolithic MIMO controller, the system segments control into independent subsystems with dedicated control loops. The arbitration logic is further segmented into separate functional stages (priority evaluation, coincidence detection, limitation), reducing adjustment complexity while maintaining coordinated control capability.
Solution Approach 2:
The arbitration and limitation logic dynamically adapts to different driving situations and subsystem priorities without requiring complete reconfiguration. The system can add or remove subsystems dynamically, and the arbitration logic automatically adjusts, improving robustness against parameter variations and aging.
Data Source
AI summary
A method for controlling a vehicle steering system having a plurality of subsystems that generate steering requests for the steering system comprising the steps of receiving a plurality of steering requests at an electronic control unit, receiving a plurality of vehicle parameter signals at the electronic control unit, the vehicle parameter signals being representative of a driving situation for each subsystem in the plurality of subsystems, setting an order of priority for application of the steering requests by the electronic control unit as a function of the driving situation for each subsystem, and controlling the application of the steering requests to the vehicle steering system in the set order of priority and within a predetermined overall torque limit.