Vehicle Longitudinal Speed Determination Using Wheel Forces
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Solution Overview
Problem
Existing methods for determining longitudinal vehicle speed are limited by their reliance on mathematical models with limited validity, requiring increased computing effort for more accurate calculations.
Innovation Solution
A method using an ESP sensor system with a speed sensor, yaw rate sensor, and lateral acceleration sensor to determine individual wheel longitudinal forces, calculating vehicle longitudinal speed based on these forces, and incorporating a non-linear Luenberger observer to estimate road surface friction and wheel dynamics with reduced computational effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If non-linear models or non-linear algorithms are used to determine vehicle speed, then measurement precision is improved, but computing effort increases
Solution Approach 1:
The patent transforms the complex non-linear vehicle dynamics problem into a linear estimation problem by changing the parameters being estimated. Instead of directly estimating vehicle speed from non-linear wheel speed data, the method estimates wheel longitudinal forces as intermediate parameters, then derives vehicle speed from these forces using a linear relationship (F=ma). This parameter transformation maintains high measurement precision while significantly reducing computing effort.
2Device complexity
If mathematical models with limited validity are used, then computing effort is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces wheel longitudinal forces as an intermediary parameter between wheel speed measurements and vehicle speed calculation. This intermediary allows the use of simplified linear models while maintaining accuracy by capturing the essential physics through the force parameter, which serves as a bridge between the measured wheel quantities and the desired vehicle speed.
Solution Approach 2:
The patent segments the vehicle dynamics problem into independent wheel-level analyses. By determining longitudinal forces for each wheel separately based on individual wheel speed measurements and then combining these to obtain vehicle speed, the method achieves high precision through distributed measurement while using computationally efficient linear calculations at each segment.
3Device complexity
If wheel speeds are determined solely from mathematical models, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism by using measured wheel speeds to update and refine the estimation of wheel longitudinal forces. The measured wheel speed data feeds into the force estimation process, and the resulting force estimates are used to calculate vehicle speed with improved accuracy. This feedback loop ensures that the system adapts to actual vehicle conditions while maintaining a relatively simple sensor configuration.
Data Source
Figure 1~4
AI summary
In a method for determining the vehicle longitudinal speed in a vehicle, a wheel longitudinal force is determined in an estimating equation as a function of the wheel speeds, and the vehicle longitudinal speed is ascertained as a function of the wheel longitudinal force.