Rear Wheel Speed Estimation From Front Wheels During Corner Braking

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Solution Overview

Problem

Existing methods fail to accurately determine the speed of rear wheels during blocking or slipping conditions, especially when direct measurement is impossible due to sensor failure, and struggle to provide precise speed evaluation for tight bends.

Innovation Solution

A module evaluates the speed of rear wheels indirectly using the speeds of the front wheels, employing a formula that incorporates the average and maximum speeds of the front wheels with a correction coefficient to estimate the rear wheel speed, enabling precise evaluation even in tight turns.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If direct measurement of rear wheel speed is used, then measurement precision is improved, but reliability deteriorates when sensor failure or wheel lockup/slippage occurs

Engineering Contradiction:

Improverear wheel speed measurement precisionVSAvoidmeasurement reliability under failure conditions

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent uses front wheel speed measurements as an intermediary to indirectly determine rear wheel speed. Instead of directly measuring the unreliable rear wheel speed, the system measures front wheel speeds and uses geometric relationships (turning radius, wheelbase) to calculate the corresponding rear wheel speed, thereby avoiding direct contact with the unreliable measurement source

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If front wheel speeds are used to evaluate rear wheel speed, then reliability is improved by avoiding sensor failure on rear wheels, but measurement precision deteriorates due to indirect calculation

Engineering Contradiction:

Improvemeasurement reliability under failure conditionsVSAvoidrear wheel speed evaluation precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent dynamically adjusts the evaluation parameters based on vehicle operating conditions. The correction coefficient is modified according to whether the vehicle is turning or moving straight, and the system selects different calculation methods based on available sensor data, thereby optimizing precision across different operating scenarios while maintaining reliability

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a simple average of front wheel speeds is used, then device complexity is reduced, but measurement precision deteriorates in turning conditions

Engineering Contradiction:

Improveevaluation system complexityVSAvoidrear wheel speed precision in tight bends

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent implements a dynamic evaluation system that adapts its calculation method based on real-time vehicle conditions. The system determines whether the vehicle is turning or moving straight, selects appropriate front wheel speed measurements, and applies dynamic correction coefficients to maintain precision across varying operating conditions without requiring complex hardware

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP3853683B1Motor vehicle control module and method, comprising an evaluation of rear wheel speed based on the front wheels only

Publication Date: 2023.12.27 HITACHI ASTEMO FRANCE

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AI summary

Disclosed is an evaluation of the speed of movement of a rear wheel (3G) of a motor vehicle on the ground, in particular on the inside of a bend, which is made exclusively according to the speeds of the front wheels (2D, 2G), in situations in which a direct measurement is not possible or in order to accurately evaluate occurrences of wheel lock-up or wheel slip. The invention can be applied to improving the braking setpoints when cornering.