Brake Friction State Estimation Without Normal Force Sensors
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Solution Overview
Problem
Existing methods for determining friction coefficients in brake systems require multiple physical parameters to be continuously recorded, including normal forces, which complicates the process and increases the need for sensors, making them less suitable for use in existing vehicles with low conversion costs.
Innovation Solution
A method that determines friction coefficients using only relative speeds and temperatures, with experimentally determined constants, eliminating the need for normal force measurements and simplifying the process by using simulated temperature values, allowing for on-board computation in vehicles without the need for additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If normal forces are measured to determine friction coefficients, then measurement precision is improved, but device complexity increases due to additional sensors and recording processes
Solution Approach 1:
The patent extracts and eliminates the requirement for normal force measurement from the friction coefficient determination process. By reformulating the calculation to use only relative speed and temperature parameters, the method removes the need for force sensors and their associated recording systems, thereby reducing device complexity while maintaining measurement capability through alternative physical parameters
Solution Approach 2:
The patent replaces the mechanical measurement approach (force sensors for normal force) with a thermal and kinematic approach (temperature sensors and speed sensors). This substitution uses temperature and relative speed as proxy indicators that can be measured more simply and fed into the polynomial calculation to derive friction coefficients without direct mechanical force measurement
2Reliability
If multiple physical parameters are continuously recorded, then reliability of friction coefficient determination is improved, but ease of operation worsens due to complex recording and processing requirements
Solution Approach 1:
The patent extracts and removes normal force measurement from the continuous recording requirements, reducing the number of parameters that need to be monitored in real-time operations. This simplifies the operational burden on vehicle systems while maintaining reliable friction coefficient determination through the remaining temperature and speed parameters combined with pre-determined polynomial constants
Solution Approach 2:
The patent performs preliminary determination of polynomial constants during brake testing before actual vehicle operation. This pre-processing step transfers complexity from operational use to setup phase, so that during normal vehicle operation, only simple temperature and speed measurements are needed without complex real-time processing, thereby improving ease of operation while maintaining reliability
3Measurement precision
If temperature measurements are used to determine friction coefficients, then measurement precision is improved, but device complexity increases due to additional sensors
Solution Approach 1:
The patent replaces mechanical force measurement with thermal measurement. By using temperature sensors instead of force sensors, the system substitutes a different physical domain (thermal) for the original mechanical domain. This substitution enables friction coefficient determination through temperature and speed data processed via polynomial relationships, achieving the desired measurement precision while using sensors that may be more integrated into existing brake system monitoring infrastructure
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 approach enables precise determination of friction coefficients with reduced operational complexity, enabling improved braking control and safety, and is suitable for use in existing vehicles with low conversion costs, ensuring precise braking distances and comfort.
Implementation Method 1
temperatures T in contact between the first friction partner and the second friction partner are determined by means of a temperature simulation, wherein contact temperatures between the first friction partner and the second friction partner are determined, for example, via a one-dimensional heat conduction equation
Data Source
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AI summary
A method for determining friction states between friction partners of a brake, wherein friction coefficients (µ) are determined from relative velocities (v) between the friction partners, temperatures (T) in contact between the friction partners, and experimentally determined constants (p). It is proposed that the friction coefficients (µ) be determined from summands s = pijviTj with a first numerator (i) and a second numerator (j), where the constants (p) are determined beforehand from experiments or brake test runs with defined contact forces (F) of a first friction partner against a second friction partner, as well as by comparisons (10) of experimental friction coefficients (µv) determined from the experiments or brake test runs with polynomials of degree n formed from the summands (s). This results in an efficient and at the same time accurate assessment of the friction states.