Road Friction Estimation Using Lateral Acceleration Without Sideslip
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Solution Overview
Problem
Existing methods for estimating road-surface friction coefficient and sideslip angle are interdependent, making it difficult to accurately estimate these parameters and adjust control in driving support systems, particularly for two-wheel vehicles.
Innovation Solution
The device and method accurately estimate road-surface friction coefficient and enable easy control adjustment by calculating lateral acceleration using wheel speed, vehicle-body roll angular velocity, and yaw rate, and performing ground coordinate conversion without relying on sideslip angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sideslip angle and road-surface friction coefficient are estimated using interdependent methods, then both parameters can be obtained, but the estimation accuracy deteriorates and control adjustment becomes difficult
Solution Approach 1:
The patent segments the estimation process into independent components: lateral acceleration is calculated separately using wheel speed and angular velocity sensors, then road-surface friction coefficient is estimated independently from this calculated acceleration without requiring sideslip angle. This segmentation breaks the interdependence cycle and improves both estimation accuracy and control adjustability.
Solution Approach 2:
The patent introduces calculated lateral acceleration as an intermediary parameter that mediates between sensor measurements and road-surface friction coefficient estimation. By using this intermediary derived from geometric relationships and sensor data, the system avoids the circular dependency between sideslip angle and friction coefficient while maintaining estimation accuracy.
2Reliability
If traditional vehicle model calculation methods are used to estimate road-surface friction coefficient, then comprehensive vehicle dynamics are considered, but the estimation becomes complex and difficult to adjust
Solution Approach 1:
The patent extracts the essential lateral acceleration component from complex vehicle dynamics models by using direct sensor measurements (wheel speed, angular velocity) and geometric relationships. This extraction simplifies the estimation process while maintaining reliability by focusing on the most critical parameters without the complexity of full vehicle model calculations.
Data Source
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AI summary
A road-surface friction coefficient estimation device includes: a lateral acceleration calculator configured to calculate an acceleration in a lateral direction using a wheel speed detected by a wheel speed sensor mounted in a vehicle, a vehicle-body roll angular velocity detected by an angular velocity sensor mounted in the vehicle, and a vehicle-body lateral velocity and a yaw rate calculated from a geometric relationship; a coordinate converter configured to convert an acceleration detected by an acceleration sensor mounted in the vehicle to a measured acceleration in the lateral direction subjected to ground coordinate conversion; and a road-surface friction estimator configured to estimate a road-surface friction coefficient using a road-surface friction model on the basis of the calculated acceleration in the lateral direction and the measured acceleration in the lateral direction.