Longitudinal Stiffness Estimation via Wear and Load Compensation
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Solution Overview
Problem
Current systems for estimating road surface friction are unreliable and inaccurate due to the inability to achieve the necessary levels and persistence of vehicle motion excitation, and they ignore significant factors that affect estimation accuracy.
Innovation Solution
A tire-based system and method that estimates longitudinal stiffness using load measurement, tire-based sensor input parameters, and a wear state estimator, with a longitudinal stiffness adaptation model that compensates for factors like air cavity pressure, temperature, and tire wear, to improve friction estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vehicle motion excitations (accelerating, decelerating, steering) are used to estimate road friction, then friction estimation can be performed, but the required level and persistence of excitation cannot be achieved in practice
Solution Approach 1:
The patent changes the estimation approach from requiring vehicle motion excitations to using tire-specific parameters (inflation pressure, temperature, wear state, construction characteristics) that can be measured without requiring specific driving maneuvers. This allows friction estimation under normal driving conditions without needing to force the vehicle into particular motion states.
Solution Approach 2:
The patent replaces the mechanical excitation requirement with a model-based estimation system that uses sensor measurements of tire parameters. Instead of relying on mechanical vehicle motions to generate estimation signals, the system substitutes this with a computational model that processes tire pressure, temperature, wear, and construction data to estimate friction coefficients.
2Measurement precision
If current friction estimation schemes are used, then estimation can be performed, but significant factors affecting accuracy are ignored
Solution Approach 1:
The patent incorporates additional tire parameters (inflation pressure, temperature, wear state, construction characteristics) into the estimation model to improve accuracy. By changing the set of parameters considered in the estimation, the system captures more of the physical factors that influence tire-road friction, thereby improving measurement precision.
Solution Approach 2:
The patent performs preliminary estimation of individual tire parameters (wear state, temperature, pressure) before combining them in the friction estimation model. This staged approach allows each parameter to be independently characterized and then integrated into the final friction coefficient estimation, improving overall accuracy while managing complexity.
3Measurement precision
If tire-specific parameters and wear state are incorporated into the estimation model, then friction estimation accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent segments the friction estimation problem into separate sub-estimations for different tire parameters (wear state, temperature, pressure, construction characteristics). Each parameter is estimated or measured independently, and then their effects are combined in the friction model. This segmentation reduces the complexity of the overall system by breaking it into manageable, independent components.
Solution Approach 2:
The patent introduces a wear state estimator as an intermediary component that bridges the gap between raw sensor data and the friction estimation model. This intermediary processes tire acceleration data to estimate wear state, which then serves as an input to the friction model. This modular intermediary approach improves accuracy while keeping the system architecture manageable.
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
The system provides a reliable and robust method for estimating road surface friction, enhancing the accuracy of vehicle control systems by incorporating tire-specific parameters and adapting to varying conditions, leading to improved vehicle safety and control.
Implementation Method 1
The wear state estimator preferably generates the wear state estimation from a detected shift in a vertical mode of the one tire
Data Source
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AI summary
A tire-based system and method for estimating a longitudinal stiffness between a tire (12) and a road surface is disclosed. The system comprises at least one tire (12) mounted to a wheel hub and supporting a vehicle (14); load measurement means for determining a load level (42) on the at least one tire (12); wear estimation means (38) for estimating a wear state of the at least one tire (12); tire-based sensor input means for measuring and/or providing tire-based input parameters (44); and longitudinal stiffness adaptation model means for deriving a longitudinal stiffness estimation (46) scaled by the load level, the tire-based sensor input parameters, and the wear state.