Road Friction Estimation Using Tire Load and Acceleration Feedback
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Solution Overview
Problem
Existing methods for estimating road friction coefficients are inaccurate and unsafe, as they only determine the coefficient when the vehicle is already losing grip, failing to provide precise values in varying road and weather conditions, which can lead to loss of vehicle controllability.
Innovation Solution
A device and method that utilize an acceleration sensor, load determination device, and tire slip determination device, along with a friction coefficient estimator, to cyclically adjust the estimated road friction coefficient based on vehicle acceleration measurements, incorporating a tire model with a feedback loop to adapt the coefficient to actual conditions, allowing for precise estimation in any driving condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel slip/slide measurements are used to estimate road friction, then friction estimation can be obtained during vehicle operation, but the estimation becomes inaccurate when wheel slip/slide occurs
Solution Approach 1:
The patent introduces an intermediary approach by using vehicle dynamics parameters (longitudinal acceleration, steering angle, brake pressure) as mediators to estimate road friction without directly relying on wheel slip measurements. This allows friction estimation to continue during wheel slip events by inferring friction characteristics from the vehicle's response to driver inputs and environmental conditions rather than from direct wheel slip data.
2Ease of manufacture
If friction estimation is based on wheel slip/slide measurements, then the method is simple to implement, but it cannot provide accurate friction values during low-friction events
Solution Approach 1:
The patent creates a universal friction estimation system that functions under multiple driving conditions (both normal and low-friction events) by integrating multiple data sources. The system uses vehicle dynamics parameters, environmental sensors, and driver behavior data together to provide accurate friction estimates across all conditions, making the estimation method universally applicable rather than condition-specific.
3Speed
If direct wheel slip measurements are used for friction estimation, then real-time friction data can be obtained, but the data is unreliable during the very low-friction events that matter most for safety
Solution Approach 1:
The patent implements a feedback mechanism where the friction estimation system continuously monitors vehicle dynamics parameters and compares predicted versus actual vehicle behavior. During low-friction events, the system uses feedback from multiple sensors (accelerometers, steering angle sensors, brake pressure sensors) to adjust and refine friction estimates in real-time, ensuring reliable data availability even during critical safety events.
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 reliable detection of changed road and weather conditions without leaving a stable driving state, providing a precise and adaptive estimation of the road friction coefficient, enhancing vehicle dynamics control and safety.
Implementation Method 1
a sensor device (130) arranged to measure a lateral acceleration of the vehicle during a predetermined manoeuvre
Data Source
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AI summary
The invention relates to a device and to a method for estimating a coefficient of friction of a road, which is present in frictional contact between an underlying surface (8) and tyre (90) of a vehicle, wherein the device (10) comprises a connection (11) for an acceleration sensor (12) for inputting a vehicle acceleration measured value (aT, aL), a load-determining apparatus (13) for determining at least one vertical tyre load (Fzi), a tyre slip-determining apparatus (14) for determining at least one tyre slip (sLi) of the tyres (90) and a coefficient of friction-estimating apparatus (15) for determining and outputting an estimated value for the coefficient of friction (f') of the road, wherein the device (10) also has an acceleration-estimating apparatus (17) which is designed to determine an estimated value for the vehicle acceleration (aL') using a tyre model (22) on the basis of at least the tyre slip (sLi), the vertical tyre load (Fzi) and an estimated value, determined in a preceding cycle, for the coefficient of friction (f') of the road, and the coefficient of friction-estimating apparatus (15) is designed to adapt the output estimated value for the coefficient of friction (f') of the road, in such way that a difference between the estimated value (aL') and the measured value (aL) of the vehicle acceleration is adjusted to a predefineable range.