Wheel Speed-Based Ground Load Estimation for Uneven Roads
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Solution Overview
Problem
Conventional techniques for estimating ground contact load in vehicles do not accurately reflect the influence of road surface unevenness, leading to insufficient accuracy in estimating vehicle ground contact load.
Innovation Solution
A ground contact load estimation device and method that utilize a wheel speed sensor to acquire physical quantities such as wheel angular speed, steady load, and inertia load, and include a road surface load estimation section with a first gain calculation and tire effective radius variation calculation to estimate road surface load, reducing the influence of wheel angular speed variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a vehicle motion model is used to estimate ground contact load from detected vehicle state quantities, then the estimation can be performed using conventional sensors, but the influence of road surface unevenness is insufficiently reflected, leading to reduced estimation accuracy
Solution Approach 1:
The patent applies preliminary action by calculating the tire effective radius variation based on wheel angular speed variations before using it to estimate road surface load. This pre-calculation of radius variation allows the system to account for road surface unevenness effects in advance, improving the accuracy of ground contact load estimation without requiring additional sensors during the actual measurement process.
Solution Approach 2:
The patent changes parameters by introducing the tire effective radius as a variable parameter that varies with road surface conditions. Instead of assuming a constant tire radius, the system calculates radius variations from wheel angular speed data and uses these variations to determine road surface load, thereby adapting the estimation model to reflect actual road surface influences.
2Device complexity
If wheel angular speed variation is directly used to calculate tire effective radius variation, then the calculation is simple, but the variation in wheel angular speed excessively influences the estimation result, reducing accuracy
Solution Approach 1:
The patent introduces a second gain as an intermediary factor between wheel angular speed variation and tire effective radius variation. This second gain moderates the direct influence of wheel angular speed variations, preventing excessive sensitivity while still capturing the essential relationship. The second gain acts as a mediator that balances calculation simplicity with estimation accuracy by scaling the radius variation appropriately.
Data Source
AI summary
The present invention achieves a technique that makes it possible to estimate a ground contact load of a vehicle with sufficiently high accuracy. A ground contact load estimation device (100) acquires a wheel angular speed, a steady load, and an inertia load of a vehicle, uses the steady load and the inertia load to cause a first gain calculation section (122) to calculate a first gain, multiplies a variation in wheel angular speed by a second gain so as to cause a tire effective radius variation calculation section (121) to calculate a tire effective radius variation, and multiplies the tire effective radius variation by the first gain so as to estimate a road surface load.