Vehicle Steering System Friction Estimation via Opposite-Phase Shift
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Solution Overview
Problem
Current vehicle steering systems lack effective methods to estimate the friction coefficient of the road surface, which is crucial for maintaining turning stability, especially in independent right-left wheel steering systems.
Innovation Solution
A steering system that includes a pair of wheel steering devices for independent right and left wheel control, employing opposite-phase shift steering to estimate the road surface friction coefficient based on steering forces applied to each wheel, while maintaining vehicle-body slip angle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If opposite-phase shift steering is executed to estimate road surface friction coefficient, then measurement precision of road surface μ is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The steering system performs multiple functions using the same hardware components. The wheel steering devices and controllers not only perform normal steering control but also execute opposite-phase shift steering for road surface friction coefficient estimation. This multi-functionality approach allows the system to gain measurement capabilities without adding dedicated estimation hardware, thereby improving measurement precision while minimizing device complexity increase.
Solution Approach 2:
The steering system uses its own operational characteristics during normal operation to estimate road surface friction coefficient. By analyzing the steering forces and wheel responses during opposite-phase shift steering that is already part of the steering control, the system self-estimates the friction coefficient without requiring external measurement devices, thus avoiding additional system complexity.
2Measurement precision
If opposite-phase shift steering is executed to estimate road surface friction coefficient, then measurement precision is improved, but loss of time occurs due to additional estimation processes
Solution Approach 1:
The road surface friction coefficient estimation process is merged with the normal steering control process. The controller executes opposite-phase shift steering and performs friction coefficient estimation in an integrated manner, using the same sensors, actuators, and control loops. This combining of functions allows the system to obtain estimation data during regular steering operations without requiring separate dedicated time or processes, thereby improving measurement precision while minimizing time loss.
3Measurement precision
If wheel steering devices receive load during opposite-phase shift steering, then measurement precision of steering force is improved, but object-generated harmful factors increase due to additional load on steering system
Solution Approach 1:
The system applies partial opposite-phase shift steering rather than full opposite-phase steering. By using controlled shift amounts that are smaller than maximum possible values, the system generates sufficient steering force variations for accurate friction coefficient estimation while keeping the additional load on the steering devices within acceptable limits. This partial action approach balances measurement precision improvement with minimizing harmful effects on the steering system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate estimation of road surface friction coefficient, allowing for enhanced stability and notification to the driver when driving on low-friction surfaces, thereby improving vehicle control and safety.
Implementation Method 1
estimate a friction coefficient of a road surface on which the vehicle is running based on steering forces respectively applied to the right and left wheels in the opposite-phase shift steering
Data Source
AI summary
A steering system for a vehicle, including: a pair of wheel steering devices that respectively steer right and left wheels independently of each other; and a controller configured to control the pair of wheel steering devices, wherein the controller is configured to: determine a standard steering amount of each of the right and left wheels in accordance with a steering request; execute opposite-phase shift steering in which steering amounts of the respective right and left wheels are shifted in mutually opposite directions by respective shift amounts with respect to the standard steering amounts determined respectively for the right and left wheels; and estimate a friction coefficient of a road surface on which the vehicle is running based on steering forces respectively applied to the right and left wheels in the opposite-phase shift steering.