Wheel Bearing Sensor Circuit Drift Compensation

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Solution Overview

Problem

Existing sensor-equipped wheel support bearing assemblies face challenges with drift due to environmental temperature and initial strain-induced drift, leading to increased manufacturing costs, complexity in circuit design, and reduced accuracy in load detection due to thermal influences and vibration susceptibility.

Innovation Solution

A compact sensor-equipped wheel support bearing assembly with a calculation processing circuit integrated into a circuit fixing stay on the vehicle body fitting flange, using a strain generating member with contact fixing segments and sensors to detect strain, and an analog-to-digital converter for accurate load estimation, while being protected by a toric protective covering to prevent environmental interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If strain sensors are used to detect load on vehicle wheels, then load detection capability is provided, but sensor drift occurs due to environmental temperature and initial strain upon fitting

Engineering Contradiction:
Improveload detection accuracyVSAvoidsensor drift
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent implements feedback by continuously monitoring sensor output signals and comparing them against reference values. The control circuit adjusts offset adjusting circuits based on feedback from temperature sensors and sensor signal analysis, automatically compensating for drift without manual intervention. This closed-loop feedback system maintains measurement accuracy despite environmental variations.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The sensor system performs self-service through automatic drift compensation mechanisms. The control circuit autonomously detects drift conditions, activates appropriate offset adjusting circuits, and restores accurate measurement capability without requiring external calibration or manual adjustment. The system serves itself by monitoring its own performance and correcting deviations.

Inventive Principle:
Principle #25Self-service

2Measurement precision

If offset adjustment circuits are added to compensate for sensor drift, then measurement accuracy is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:
Improvesensor output accuracyVSAvoidcircuit configuration
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs dynamic circuit configuration where offset adjusting circuits are selectively activated based on operating conditions. The control circuit dynamically switches between different offset compensation strategies (temperature-based, signal-based, or combined) depending on the detected drift source, optimizing the balance between accuracy and complexity for each specific situation.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system changes operational parameters by adjusting offset values in response to detected drift conditions. The control circuit modifies circuit parameters (offset amounts, activation states) based on temperature readings and sensor signal characteristics, dynamically adapting the measurement system to current environmental and operational conditions without permanent structural changes.

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If multiple strain sensors are deployed on the wheel bearing assembly, then load detection coverage is improved, but susceptibility to thermal influences and vibration increases

Engineering Contradiction:
Improveload detection coverageVSAvoidthermal influence and vibration susceptibility
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces temperature sensors as intermediary elements that mediate between the environmental thermal conditions and the strain sensors. These intermediary temperature sensors detect thermal changes and trigger compensatory actions in the control circuit, which then adjusts the strain sensor readings to account for thermal effects, protecting the measurement system from direct thermal interference.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The system uses feedback from temperature sensors and sensor signal analysis to detect thermal drift and vibration-induced errors. The control circuit processes this feedback information and applies corrective offset adjustments to the strain sensor outputs, continuously compensating for harmful environmental factors affecting multiple sensors deployed on the bearing assembly.

Inventive Principle:
Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution enables accurate and reliable load detection with reduced manufacturing costs and improved assemblability, minimizing errors and delays in load estimation, enhancing the controllability and stability of automotive vehicles.

Implementation Method 1

a strain sensor fixed to this strain generating member for detecting a strain occurring in the strain generating member

Methodology Applied
Scientific EffectStrain detection: Piezoresistive Effect

Data Source

PatentEP2578895B1Sensor-equipped wheel bearing
Publication Date: 2019.09.04 NTN CORP
  • EP2578895B1 patent drawingFigure 1
  • EP2578895B1 patent drawingFigure 2
  • EP2578895B1 patent drawingFigure 3

AI summary

A sensor equipped wheel support bearing assembly having good assemblability with a compact structure and capable of accurately detecting load acting on a bearing of a vehicle wheel is provided. One of an outer member and an inner member that serves as a stationary member has a vehicle body fitting flange to be fitted to a knuckle. One or more load detecting sensor unit is provided on the stationary member and includes a strain generating member having two or more contact fixing segments fixed to the stationary member, and one or more sensors fitted to the strain generating member for detecting a strain occurring in the strain generating member. A circuit fixing stay is provided on a side face of the vehicle body fitting flange and a calculation processing circuit is fitted to this stay for calculating and processing an output signal of the sensor.