Steer-By-Wire Feedback Torque for Adhesion Limit Awareness
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Solution Overview
Problem
In vehicles with steer-by-wire systems, drivers lack the ability to feel when the vehicle is operating near or at its limit of adhesion due to the absence of a direct mechanical connection between the driver and the wheels.
Innovation Solution
A method and system that provides driver feedback through actuators and electro-mechanical devices in the steer-by-wire system, using a reference and target model to estimate responsive rack forces and determine a corrected responsive rack force, which is then used to generate a driver feedback torque to simulate the feel of approaching adhesion limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a steer-by-wire system is used to provide steerage via actuators without direct physical linkage, then the complexity of the steering system is reduced and control precision is improved, but the driver's ability to feel when the vehicle is operating near or at its limit of adhesion is lost
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors wheel forces and adhesion conditions, then provides tactile feedback to the driver through the steering wheel actuator. This closed-loop feedback system restores the driver's awareness of adhesion limits while maintaining the precision benefits of steer-by-wire control.
Solution Approach 2:
The steering wheel actuator serves as an intermediary that transfers information about wheel forces and adhesion conditions to the driver. Instead of direct mechanical linkage, the actuator mediates between the electronic control system and the driver's tactile senses, providing force feedback that indicates approaching adhesion limits.
2Loss of information
If direct physical linkage is used between driver and wheels, then the driver can feel when the vehicle is operating near or at its limit of adhesion, but the steering system complexity increases and control precision decreases
Solution Approach 1:
The patent replaces the direct mechanical linkage system with an electro-mechanical steer-by-wire system. Sensors, actuators, and control algorithms substitute for traditional mechanical connections, enabling precise digital measurement and control of steering parameters while maintaining driver feedback through controlled force application to the steering wheel.
3Reliability
If steer-by-wire actuators are used without force transferring mechanical connection, then system reliability is improved through reduced mechanical wear, but the driver loses tactile feedback about wheel adhesion conditions
Solution Approach 1:
The system employs feedback mechanisms that monitor wheel forces, suspension kinematics, and adhesion conditions, then translate this information into tactile feedback forces applied to the steering wheel. This maintains driver awareness of adhesion conditions while preserving the reliability benefits of reduced mechanical wear in the steering system.
Data Source
AI summary
A steer-by-wire system configured for providing driver feedback to enable a driver of a vehicle to feel when the vehicle may be operating near or at its limit of adhesion. The driver feedback may be determined based on a corrected responsive rack force derived as a function of an observed responsive rack force, a reference responsive rack force, a target responsive rack force, and/or a minimum saturation value.