Road Surface Friction Estimation with Disturbance Range Correction
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Solution Overview
Problem
Existing driver assistance systems face challenges in accurately estimating the maximum friction coefficient between a road surface and a vehicle's tire, especially when influenced by aperiodic disturbances such as pebbles or road depressions, leading to excessive variation in estimated values.
Innovation Solution
A road surface friction estimation device that calculates a provisional maximum friction value based on detected physical quantities during vehicle travel. It uses a range determination part to establish a determination range based on the average and standard deviation of provisional values, and a second estimation part to correct the provisional value to a more stable estimated maximum friction value when it falls outside this range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the maximum friction coefficient is estimated based on detected physical quantities during vehicle travel, then the estimation responsiveness is improved, but the measurement precision deteriorates due to aperiodic disturbances such as pebbles or road depressions causing excessive variation in estimated values
Solution Approach 1:
The system performs preliminary actions by repeatedly calculating provisional maximum friction values over a predetermined period before final determination. This allows the system to gather multiple data points and establish a determination range (average ± standard deviation) in advance, so that when the final estimation is made, it can filter out aperiodic disturbances by comparing against the pre-established range, thus improving precision without sacrificing responsiveness
Solution Approach 2:
The system implements feedback by using the determination range (based on average and standard deviation of provisional values) to validate subsequent friction coefficient estimations. When a newly calculated provisional value falls outside the determination range, the system detects this as an anomaly caused by aperiodic disturbances and corrects it by adjusting to the upper or lower bound of the determination range, thereby maintaining measurement precision while preserving real-time estimation capability
2Measurement precision
If multiple provisional maximum friction values are calculated and a determination range is established using average and standard deviation, then the measurement precision is improved by filtering disturbances, but the device complexity increases due to additional calculation steps
Solution Approach 1:
The system applies self-service by using its own calculated provisional values to automatically establish the determination range and perform self-correction. The average and standard deviation are computed from the system's own data, and the correction logic automatically adjusts outlying values without external intervention. This self-contained approach improves precision while minimizing additional complexity, as the system serves itself rather than requiring external calibration or complex additional hardware
Data Source
AI summary
A road surface friction estimation device includes: a first estimation part to calculate a provisional maximum friction value based on a physical quantity in relation to friction between a road surface and a tire; a range determination part to determine a determination range of the provisional maximum friction value based on an average value and a standard deviation of the provisional maximum friction values; and a second estimation part to determine the provisional maximum friction value as an estimated maximum friction value when the provisional maximum friction value is within the determination range. The second estimation part determines a corrected value, which is a value within the determination range, as the estimated maximum friction value when the provisional maximum friction value is out of the determination range.