Steering Return Moment via Rack Force
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Solution Overview
Problem
Existing electromechanical and steer-by-wire steering systems face issues with control stability, predictability, and complexity in determining target steering moments, leading to unwanted steering behavior and inefficiencies in adapting to vehicle parameters and road friction changes.
Innovation Solution
A method that determines the steering return moment requirement based on rack force, which is independent of steering feel tuning, using a proportional control loop with function values derived from rack force and vehicle speed, allowing for direct consideration of road friction and improved control speed and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If driver moment and steering wheel angular velocity are used as input variables for determining damping moment and hysteresis moment, then steering feel can be adjusted, but control stability deteriorates due to intrinsic feedback loops
Solution Approach 1:
The patent extracts the problematic feedback loop by replacing driver moment and steering wheel angular velocity with rack force as the input variable. Rack force is measured directly from the steering system and does not depend on the actuator output, thereby removing the intrinsic feedback loop that causes control instability while preserving the ability to adjust steering feel through proportional control.
Solution Approach 2:
The patent introduces rack force as an intermediary variable that mediates between the steering system's mechanical state and the control algorithm. This intermediary provides a stable, direct measurement that is independent of the actuator's steering feel adjustments, allowing the system to maintain control stability while still enabling steering feel customization through proportional control gains.
2Adaptability or versatility
If steering moment is used as input variable for determining return moment and damping moment, then steering feel can be adapted, but control speed deteriorates due to additional processing loops
Solution Approach 1:
The patent extracts the unnecessary processing step by using rack force directly instead of computing steering moment from multiple other variables. This eliminates an entire layer of calculation and feedback processing, significantly increasing control speed while maintaining the ability to adapt steering feel through proportional control parameters.
3Adaptability or versatility
If multiple input variables including driver moment are used for determining individual moments, then steering feel can be customized, but device complexity increases
Solution Approach 1:
The patent extracts and removes the complex multi-variable computation chain by replacing it with a single direct measurement of rack force. This simplifies the control algorithm significantly, reducing the number of required sensors and calculations, while steering feel customization is maintained through proportional control gains applied to the rack force signal.
4Adaptability or versatility
If scaling factors are applied to account for vehicle parameters like weight, then steering feel consistency can be improved, but the system requires additional adjustments of multiple functions
Solution Approach 1:
The patent applies universality by using rack force as a single input variable that inherently captures the effects of vehicle parameters such as weight and road friction. This single measurement serves multiple functions simultaneously, eliminating the need for separate scaling factors and multiple adjustment functions, thereby maintaining steering feel consistency across different vehicle configurations without increasing system complexity.
Data Source
AI summary
The present disclosure relates to a method for determining a steering return moment requirement of a steering device of a vehicle, to a steering system, to a computer program product, and to a computer-readable storage medium. The steering device is part of a steering system of the vehicle, and is coupled to at least one actuator. The actuator is configured to apply a steering moment to the steering device. The method comprises at least the step of determining the steering return moment requirement based on at least one rack force of the steering system. The steering return moment requirement forms at least a portion of a target steering moment which can be applied to the steering device by the at least one actuator.