Steering Torque Modifier for Understeer Feedback
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Solution Overview
Problem
Existing steering systems, particularly steer-by-wire (SbW) systems, struggle to provide sufficient tactile feedback to drivers during limit understeer or oversteer conditions, which can impair the driver's ability to control the vehicle effectively.
Innovation Solution
The method involves calculating handwheel torque modifiers based on yaw rate and yaw acceleration errors, which are then applied to adjust the reference torque. This adjustment enhances tactile feedback to the driver, indicating the vehicle's state of understeer or oversteer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If steer-by-wire systems are used to enable precise steering control, then steering precision is improved, but tactile feedback to the driver is reduced
Solution Approach 1:
The system implements a feedback mechanism where yaw rate and yaw acceleration sensors detect actual vehicle motion, compare it with reference values, and generate torque modifiers that are applied to the handwheel torque control. This closed-loop feedback restores tactile feedback about vehicle state (understeer/oversteer) to the driver through the steering wheel, resolving the information loss caused by steer-by-wire decoupling.
Solution Approach 2:
The patent introduces an intermediary control system that includes a yaw rate sensor, yaw acceleration sensor, and torque modifier calculator. This intermediary layer translates vehicle dynamic state into tactile feedback forces applied to the handwheel, mediating between the decoupled steering input and vehicle response while preserving driver awareness of vehicle behavior.
2Loss of information
If traditional steering systems are used to provide natural tactile feedback, then driver awareness of vehicle state is improved, but control precision during limit conditions is reduced
Solution Approach 1:
The system dynamically adjusts handwheel torque based on real-time vehicle state through torque modifiers that change with yaw rate error and yaw acceleration error. This dynamic adjustment provides context-appropriate tactile feedback that adapts to driving conditions, enhancing driver awareness during transient and limit conditions while maintaining precision through electronic control.
Solution Approach 2:
The patent changes the parameter of handwheel torque by applying torque modifiers that are functions of yaw rate error and yaw acceleration error. This parameter modification allows the system to vary tactile feedback characteristics based on vehicle dynamic state, providing enhanced driver awareness during understeer and oversteer conditions while maintaining control precision.
3Loss of information
If handwheel torque is increased to provide stronger feedback during understeer, then driver awareness is improved, but steering effort increases
Solution Approach 1:
The system applies counterbalancing torque modifiers that provide tactile feedback about understeer condition without creating excessive steering effort. The yaw rate error-based torque modifier generates a counteracting force that informs the driver of the understeer state while the electronic control system manages the magnitude to avoid excessive steering effort, balancing information provision with operational ease.
Data Source
AI summary
A method for controlling handwheel torque in a steering system of a vehicle includes obtaining at least one of a reference yaw rate of the vehicle and a reference yaw acceleration of the vehicle, obtaining at least one of a yaw rate error and a yaw acceleration error based on the at least one of the reference yaw rate and the reference yaw acceleration, obtaining a handwheel torque modifier based on the at least one of the yaw rate error and the yaw acceleration error, adjusting a reference torque using the handwheel torque modifier, and controlling the handwheel torque using the reference torque as adjusted using the handwheel torque modifier.