Variable Magnetization Position Sensor for Accurate Long-Stroke Measurement
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Solution Overview
Problem
Existing magnetic position sensors face limitations such as hysteresis due to ferromagnetic pieces and temperature-dependent remnant induction, which affects their accuracy and practicality for long travel strokes, especially in rotary and curvilinear movements, and require multiple probes increasing costs and complexity.
Innovation Solution
A magnetic position sensor using a permanent magnet with varying magnetization direction, where the tangential, normal, and transverse components of the magnetic field vary sinusoidally, allowing for precise position measurement without relying on remnant induction, and can be implemented with a flexible magnet and magnetosensitive elements to achieve long travel strokes and reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a permanent magnet with constant magnetization is used in a magnetic position sensor, then the sensor structure is simple, but the measurement accuracy is affected by temperature-dependent remnant induction and hysteresis
Solution Approach 1:
The patent changes the magnetization parameter from constant to spatially variable, creating a magnetization pattern that varies along the movement direction. This allows the magnetic field to encode position information directly, making the measurement independent of remnant induction variations and temperature effects.
2Length of moving object
If multiple probes are used to measure long travel strokes, then the measurement range is extended, but the sensor cost and complexity increase
Solution Approach 1:
The patent transitions from using multiple discrete probes along the travel stroke to using a single probe that measures the magnetic field of a magnet with spatially varying magnetization. The position information is encoded in the magnetic field pattern, allowing a single probe to determine position anywhere along the travel stroke by detecting the local field characteristics.
3Strength
If ferromagnetic pieces are used in the sensor structure, then the mechanical strength is improved, but hysteresis effects occur that affect measurement accuracy
Solution Approach 1:
The patent removes ferromagnetic pieces from the sensor structure, replacing them with non-magnetic materials. This eliminates the hysteresis effects caused by ferromagnetic materials while maintaining the necessary mechanical strength through alternative structural design, thereby improving measurement accuracy.
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 position measurement independent of temperature variations and remnant induction, reduces sensor complexity, and allows for cost-effective implementation of long travel strokes in rotary and curvilinear movements by using a flexible magnet and standard magnetoresistive probes, enhancing robustness and precision.
Implementation Method 1
the magnet presents a magnetization direction that varies substantially linearly in the movement direction... generates a magnetic field whose normal component (Y), and at least one of the components constituted by its tangential component (X) and by its transverse component (Z)... vary periodically with N periods
Implementation Method 2
at least one magnetosensitive element that are mounted to move relative to each other... using a flexible magnet and magnetosensitive elements
Data Source
AI summary
A magnetic sensor of rotary, linear, or curvilinear displacement using at least one permanent magnet and at least one magnetosensitive element, which can move with respect to one another. The magnet exhibits a direction of magnetization that varies continuously along the direction of displacement, with the exclusion of a diametral magnetization in the case of a rotary sensor.