Wheel Traction Estimation Using Electromagnetic Speed Sensing
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Solution Overview
Problem
Existing methods for estimating the coefficient of friction between vehicle tires and road surfaces lack accuracy and reliability, especially in complex road topologies and varying weather conditions, which can impact vehicle safety.
Innovation Solution
An onboard measurement system that radiates electromagnetic energy and receives reflections to measure longitudinal acceleration and speed, allowing for the estimation of a virtual wheel radius, which is used to distinguish between different road surfaces and conditions, thereby estimating the coefficient of friction with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to estimate the coefficient of friction, then the estimation can be obtained, but the accuracy and reliability are insufficient, especially in complex road topologies and varying weather conditions
Solution Approach 1:
The patent replaces conventional mechanical sensor-based measurement systems with an electromagnetic radiation-based measurement system. The system radiates electromagnetic energy and receives reflections to measure longitudinal acceleration and speed, thereby estimating virtual wheel radius and coefficient of friction without direct mechanical contact with the road surface. This substitution enables accurate measurements in complex road topologies and varying weather conditions where mechanical sensors would fail.
Solution Approach 2:
The patent introduces electromagnetic energy as an intermediary medium to indirectly measure road surface properties. Instead of directly measuring friction between tires and road, the system uses electromagnetic radiation reflection characteristics to infer longitudinal speed and acceleration, which are then used to calculate the coefficient of friction. This indirect measurement approach allows reliable estimation under varying weather and road conditions.
2Measurement precision
If an onboard measurement system radiating electromagnetic energy is used, then high accuracy measurement of longitudinal speed and differentiation of road surfaces is achieved, but the device complexity increases
Solution Approach 1:
The onboard measurement system is designed to perform multiple functions: it measures longitudinal speed, determines longitudinal acceleration, estimates virtual wheel radius, and differentiates road surface conditions all through a single electromagnetic radiation and reception mechanism. This multi-functionality reduces the need for separate specialized sensors for each measurement type, thereby managing device complexity while achieving high measurement precision across multiple parameters.
3Measurement precision
If multiple data acquisitions are performed to build a data pool for accurate coefficient of friction estimation, then the estimation accuracy improves, but the measurement time and latency increase
Solution Approach 1:
The system continuously performs data acquisitions and builds a data pool of virtual wheel radius measurements in advance, even before a specific coefficient of friction estimation is needed. By maintaining an ongoing data collection process during normal vehicle operation, the system accumulates sufficient data for accurate estimation without requiring extended measurement periods when estimation is actually required, thus reducing latency while maintaining precision.
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 highly accurate measurement of longitudinal speed with low latency and can differentiate between various road surfaces, enhancing safety by accurately estimating the coefficient of friction, even in complex ambient road topologies.
Implementation Method 1
an onboard measurement system that radiates electromagnetic energy and receives reflections of the electromagnetic energy reflected from ambient terrestrial objects
Implementation Method 2
measuring a longitudinal acceleration and a longitudinal speed of the vehicle relative to a plurality of ambient terrestrial objects
Data Source
AI summary
A method, comprising: measuring a rotational speed of a wheel of a vehicle, determining a longitudinal acceleration of the vehicle relative to a plurality of ambient terrestrial objects using a measurement system onboard the vehicle, determining a longitudinal speed of the vehicle relative to the plurality of ambient terrestrial objects using the measurement system, judging a slippage state of the vehicle using the longitudinal acceleration, and if a result of the judging indicates the vehicle is in a low-slippage state, estimating a coefficient of traction using the rotational speed and the longitudinal speed, wherein the measurement system is structured to radiate electromagnetic energy and to receive reflections of the electromagnetic energy reflected from the plurality of ambient terrestrial objects.