Steering Feel Function for Safe Manual Force Limits
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Solution Overview
Problem
Existing motor vehicle steering systems, particularly steer-by-wire systems, face challenges in ensuring safe actuation forces on the steering wheel, as faulty detection can lead to unacceptably high or low manual forces, increasing technical efforts and financial costs due to the need for stringent safety goals application across mechanical and communication networks.
Innovation Solution
A method and system that utilize a steering mechanism with a manually operable element, a manual actuator, and a transmission component, where operating values of total transmission force are transmitted to a steering feel function to determine input values for the manual actuator, which are then limited or increased to predefined maximum and minimum values to ensure safe manual forces, using a software-assisted system function and control unit to maintain forces within defined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If safety goals are applied to the steering actuator and communication network in steer-by-wire systems, then safety and reliability are improved, but device complexity and financial costs increase
Solution Approach 1:
The patent replaces complex mechanical safety systems with a software-based steering feel function that calculates and limits manual forces through computational methods. The system uses operating values from sensors and applies software-based force determination and limiting, substituting mechanical safety mechanisms with electronic/software-based solutions that reduce hardware complexity while maintaining safety goals.
2Ease of operation
If the manual actuator applies forces based on detected transmission forces, then steering assistance is improved, but unsafe manual forces may occur if detection is faulty
Solution Approach 1:
The patent implements a feedback mechanism where the steering feel function continuously receives operating values from the steering actuator, calculates the required manual forces, and applies limiting to ensure forces remain within safe ranges. The system monitors transmission forces and adjusts manual actuator forces accordingly, creating a closed-loop control that prevents unsafe forces while maintaining steering assistance.
Solution Approach 2:
The patent applies preliminary anti-action by implementing force limiting within the steering feel function before unsafe forces can be applied to the steering wheel. The system proactively calculates and caps manual forces to predefined maximum and minimum values, preventing potentially harmful forces from reaching the driver while still providing necessary steering assistance.
3Reliability
If a mechanical connection exists between steering wheel and steering gear, then force transmission is reliable, but safety goals must be strictly applied to the steering actuator
Solution Approach 1:
The patent makes the steering feel function multi-functional by having it perform both the traditional steering assistance function and the safety function of limiting manual forces. This single software component handles multiple responsibilities: calculating required forces based on operating values, determining manual actuator forces, and applying safety limits. This consolidation reduces the need for separate safety systems while maintaining both force transmission reliability and safety goals.
Data Source
AI summary
A method for steering a motor vehicle by a steering mechanism. The steering mechanism has an actuating element, a manual actuator, a steering actuator, at least one transmission component, and a steering feel function. The steering actuator is connected to at least one steerable wheel of the motor vehicle via the at least one transmission component. The actuating element and the manual actuator are mechanically connected to each other. Operating values of a total transmission force acting on the at least one transmission component are transmitted to the steering feel function, which is used to determine input values of a manual force for the manual actuator from the determined operating values for the entire transmission force. The input values are transmitted to a system function for limiting the input values and compared to a predefined maximum value and a predefined minimum value for the actuating force by the system function.