Wheel Load Estimation Using Weighted Frequency Band Ratios
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Solution Overview
Problem
Existing wheel load estimation methods, such as those described in JP 2019-113373A, do not account for the non-uniform change in the gain of the frequency spectrum with respect to changes in wheel load across different frequency bands, leading to inaccuracies in wheel load estimation.
Innovation Solution
A wheel load estimation device and method that calculates front-to-rear and left-to-right load ratios using specific frequency bands and weighted linear combinations of gain ratios, derived from wheel speed information, to accurately estimate wheel loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain in the frequency spectrum of wheel acceleration is used to estimate wheel load, then the estimation can be performed with simple equipment, but the accuracy is insufficient because the gain does not exhibit uniform change with respect to wheel load across the entire frequency band
Solution Approach 1:
The frequency spectrum is divided into multiple frequency bands (first frequency band and second frequency band) instead of using the entire frequency spectrum. This segmentation allows the system to capture the non-uniform relationship between gain and wheel load at different frequencies, improving estimation accuracy while maintaining simple equipment requirements.
Solution Approach 2:
Different frequency bands are treated with different weighting coefficients in the linear combination. The first frequency band and second frequency band have different characteristics in terms of gain change with wheel load, so assigning different weights optimizes the local contribution of each band to the overall estimation, resolving the non-uniformity issue.
2Measurement precision
If the gain integral of the frequency spectrum is used to calculate load ratios, then the calculation is simple, but the estimation accuracy is insufficient due to non-uniform gain change across frequency bands
Solution Approach 1:
The frequency spectrum is segmented into multiple bands, and the gain is calculated separately for each band. This segmentation enables the system to account for the non-uniform relationship between gain and wheel load at different frequencies, improving accuracy while maintaining computational simplicity through the use of linear combination with weighting coefficients.
Solution Approach 2:
Weighting coefficients are introduced to adjust the contribution of each frequency band to the overall gain calculation. By changing the parameters (weighting coefficients) based on the characteristics of different frequency bands, the system achieves more accurate wheel load estimation while keeping the calculation process relatively simple.
Data Source
AI summary
A wheel load estimation device includes a wheel speed acquisition unit, a frequency characteristic ratio calculation unit, a load ratio calculation unit, and a wheel load calculation unit. The wheel speed acquisition unit acquires wheel speed information of each wheel included in the vehicle. The frequency characteristic ratio calculation unit calculates a front-to-rear frequency characteristic ratio and a left-to-right frequency characteristic ratio. The load ratio calculation unit calculates the front-to-rear load ratio and the left-to-right load ratio. The wheel load calculation unit calculates, a wheel load ratio representing a relative wheel load among the wheels included in the vehicle, for at least one of the wheels of the vehicle. The load ratio calculation unit calculates the front-to-rear load ratio by taking a linear combination of the calculated two or more front-to-rear gain ratios using weights that are different from one another.