Friction Estimation via Controlled Wheel Slip
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Solution Overview
Problem
Existing driver assistance systems, such as AEBS, rely on initial estimates of road friction that may deviate from actual conditions, leading to suboptimal performance if the initial estimate differs from the actual coefficient of friction.
Innovation Solution
A method where a first wheel of a vehicle is braked to induce a controlled slip, allowing determination of the coefficient of friction based on its behavior, which is then used to estimate the friction for other wheels under the assumption of homogeneous grip, with the first wheel being subjected to lower load and braked more severely than the second wheel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wheel is braked to induce strong slip for accurate friction determination, then measurement precision improves, but vehicle deceleration increases causing potential loss of control
Solution Approach 1:
The invention segments the wheel braking process into two distinct phases: a first braking phase with lower deceleration for accurate friction measurement, and a second braking phase with higher deceleration for actual braking performance. This segmentation allows the system to separate the measurement function from the braking function, achieving precise friction determination without compromising vehicle control.
Solution Approach 2:
The system performs preliminary friction measurement during the first braking phase before executing the main braking operation. By determining the coefficient of friction in advance through controlled slip induction at lower deceleration, the system prepares accurate friction data that will be used to optimize the second braking phase, ensuring both measurement accuracy and braking effectiveness.
2Loss of time
If initial friction estimate is used for braking systems, then system response time is reduced, but braking performance deteriorates when estimate deviates from actual friction
Solution Approach 1:
The system performs preliminary friction measurement during the first braking phase before executing the main braking operation. By determining the coefficient of friction in advance through controlled slip induction at lower deceleration, the system prepares accurate friction data that will be used to optimize the second braking phase, ensuring both measurement accuracy and braking effectiveness.
Solution Approach 2:
The system uses the measured coefficient of friction from the first braking phase to provide feedback for optimizing the second braking phase. This feedback mechanism ensures that the braking system adapts to actual road conditions, improving braking performance and reliability while maintaining rapid response time.
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
This method provides a more reliable and rapid determination of road friction, enabling improved calibration and performance of braking systems, particularly during emergency braking scenarios.
Implementation Method 1
a first wheel of a vehicle is braked in such a way that slippage between the first wheel and a roadway is smaller than slippage between a second wheel of the vehicle and the roadway... a coefficient of friction between the first wheel and the roadway is determined based on the behavior of the first wheel during braking
Data Source
Figure 1
AI summary
The invention relates to a method for determining coefficients of friction, wherein a first wheel of a vehicle is braked in such a way that a slip between the first wheel and a roadway is less than a slip between a second wheel of the vehicle and the roadway. A coefficient of friction between the first wheel and the roadway is determined on the basis of the behavior of the first wheel during the braking.