Steering Wheel Torque Feedback via Rack Force Characteristic Curve
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Solution Overview
Problem
Steer-by-wire systems lack the ability to adjust tactile feedback effectively, resulting in an unnatural steering feel for drivers, as they do not mechanically couple the steering wheel and steering gear assembly, making it difficult to simulate the forces that would typically provide a realistic steering experience.
Innovation Solution
The introduction of a characteristic curve that defines the relationship between the steering wheel torque generated by an actuator and the rack force, allowing for a more realistic and natural steering feel by mechanically coupling the actuator to the steering wheel, which can be used in both steer-by-wire and superimposed systems, and determining the rack force through models or sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a steer-by-wire system is used with mechanical decoupling between the steering wheel and steering gear assembly, then the steering system can be simplified and controlled more precisely, but the tactile feedback and steering feel become unnatural and less realistic
Solution Approach 1:
The patent replaces the mechanical coupling between steering wheel and steering gear assembly with an electrical/control system. An actuator generates steering wheel torque based on electrical signals from the control unit, eliminating the need for direct mechanical connection while maintaining steering functionality. This substitution enables precise control but loses natural tactile feedback.
Solution Approach 2:
The patent introduces an intermediary actuator system between the steering wheel and steering gear assembly. The actuator serves as a mediator that receives control signals and generates appropriate steering wheel torque, allowing the system to maintain steering control without direct mechanical coupling. This intermediary enables automated control while attempting to simulate natural steering characteristics.
2Device complexity
If the steering wheel torque is generated without considering the rack force, then the control system is simpler, but the tactile feedback cannot accurately reflect the actual operating state and mechanical resistance of the steering gear assembly
Solution Approach 1:
The patent implements a feedback mechanism where the control unit receives information about the actual operating state of the steering gear assembly (including rack force) and uses this feedback to adjust the steering wheel torque generation. The actuator generates torque that reflects the current mechanical conditions, providing accurate tactile feedback to the driver while maintaining controlled complexity in the system.
Data Source
AI summary
Generating a steering wheel torque (ML) on a steering wheel in a vehicle steering system as a tactile feedback. A value for a rack force (FZ) may be obtained, and at least a component (MZ) of an actuator-generated target steering wheel torque (MS) utilizing a characteristic curve (K1) that defines the steering wheel torque (MS) as a function of the rack force (FZ). A steering wheel torque (ML) is generated on the basis of the target steering wheel torque (MS) using an actuator mechanically connected to the steering wheel. A steering system for a vehicle, and a control unit for such a steering system may be configured to perform the functions disclosed herein.