Coilless Magnetostrictive Stress Sensor for Brake Caliper Force Measurement
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Solution Overview
Problem
Traditional stress sensors have limitations in design flexibility and sensitivity, particularly in applications like electric motor-operated brake calipers, where accurate force measurement is crucial and existing coilless sensors lack robustness in measuring low inductance values and impedance changes.
Innovation Solution
A coilless stress sensor system utilizing a band of conductive and magnetostrictive material with a processor to measure inductance, resistance, and impedance changes, and a 4-wire connection measuring circuit to enhance sensitivity and accuracy, allowing for use in various applications including electric brake caliper assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional wire coil stress sensor is used, then the sensor can measure stress through inductance changes, but the sensor lacks design flexibility and has manufacturing tolerance issues with air gaps
Solution Approach 1:
The patent merges the coil and core member into a single integrated magnetostrictive band structure. The conductive magnetostrictive material serves both as the sensing element and the magnetic core, eliminating the need for separate coil windings and air gaps. This integration provides design flexibility while eliminating manufacturing tolerance issues associated with air gaps between separate components.
Solution Approach 2:
The patent uses composite magnetostrictive materials that combine electrical conductivity and magnetostriction in a single material system. This allows the sensor to function without separate coil and core components, providing design flexibility while maintaining manufacturing precision through the elimination of air gaps.
2Manufacturing precision
If a coilless sensor is used to eliminate air gaps, then manufacturing precision improves, but the sensor lacks robustness in measuring low inductance values and impedance changes
Solution Approach 1:
The patent changes the measurement parameters by measuring not only inductance but also resistance and impedance of the magnetostrictive band. This multi-parameter measurement approach provides robustness in detecting stress-induced changes, enabling accurate measurement of low inductance and impedance variations while maintaining the manufacturing precision benefits of the coilless design.
Solution Approach 2:
The patent introduces a measuring circuit as an intermediary system that processes the electrical signals from the magnetostrictive band. This measuring circuit, combined with the processor, enables robust measurement of low inductance and impedance changes by properly conditioning and analyzing the signal, while the coilless design maintains manufacturing precision.
3Device complexity
If a simple measuring circuit is used, then device complexity is reduced, but sensitivity and accuracy for force measurement are insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the processor receives measurements from the measuring circuit and calculates stress values. This feedback loop enables the system to process multiple parameters (inductance, resistance, impedance) and provide accurate force measurements while maintaining reasonable device complexity through automated signal processing.
Solution Approach 2:
The patent makes the measuring circuit multi-functional by enabling it to measure multiple electrical parameters (inductance, resistance, impedance) simultaneously. This multi-functionality increases sensitivity and accuracy for force measurement without proportionally increasing device complexity, as a single circuit performs multiple measurement tasks.
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 system provides improved sensitivity and design flexibility for stress measurement, enabling accurate force detection in diverse applications with low inductance and impedance measurement capabilities, and is suitable for electric brake caliper assemblies.
Implementation Method 1
The core member is formed from a magnetostrictive material. A stress applied to the core member changes the magnetic permeability of the core member.
Implementation Method 2
An electrical current flowing through the wire coil establishes a magnetic field that surrounds the wire coil and propagates into the core member.
Data Source
AI summary
A system for measuring stress including a coilless sensor including at least one band of electrically conductive and magnetostrictive material, the band having a first end and a second end defining a gap therebetween, a measuring circuit electrically connected to the first and second ends of the coilless sensor, the measuring circuit being configured to pass a current through the coilless sensor and measure at least one of an inductance, a resistance and an impedance of the coilless sensor in response to the current, and a processor in electrical communication with the measuring circuit, the processor being configured to calculate an amount of stress being applied to the coilless sensor based upon the measured inductance, resistance and impedance.