Contactless Magnetic Linear Position Sensor Using Dual Magnet Geometry
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Solution Overview
Problem
Existing magnetic position sensors face challenges in providing a compact, easy-to-manufacture, and linear signal output without requiring flux directors, while also operating effectively in high temperature, high humidity, and high vibration environments.
Innovation Solution
The solution involves arranging two magnets at a predetermined angle, typically 90 degrees, to produce a substantially uniform magnetic flux density, allowing for contactless linear position measurement by calculating the difference in magnetic fields at the start- and end-points of the travel path, which is linearly dependent on the distance moved. This setup uses small, cylindrical or rod-shaped magnets and can be adapted for various applications by adjusting the angle and sensor placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If one or two larger magnets are used to modify the magnetic flux lines to obtain a linear response, then the measurement precision is improved, but the device complexity and size increase significantly
Solution Approach 1:
The patent divides the magnetic field generation function into multiple smaller magnets arranged in a specific geometric pattern (e.g., square or rectangular configuration with alternating polarities). This segmentation allows the creation of a controlled magnetic flux distribution that produces a linear response, avoiding the need for single large complex magnets while maintaining measurement precision.
2Measurement precision
If flux directors are added to modify the magnetic field to achieve linear output, then the measurement precision is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent removes the need for flux directors by directly configuring the magnets themselves to produce the desired magnetic flux distribution. The magnets are arranged in specific geometric patterns with alternating polarities, which inherently create the linear magnetic field response without requiring additional flux-directing components, thereby simplifying manufacturing.
3Measurement precision
If the magnet dimensions are made as large as the distance range to be measured, then the linear response is improved, but the device size and volume increase
Solution Approach 1:
The patent transitions from using large single-dimension magnets to using multiple smaller magnets arranged in a two-dimensional or three-dimensional geometric configuration. This dimensional change allows the creation of an extended magnetic field coverage area without proportionally increasing the volume of individual magnets, achieving linear response across the measurement range while maintaining compact size.
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
This approach results in a compact, cost-effective, and accurate linear position sensor that provides a linear output, effectively canceling out ambient field contributions and allowing for precise measurement of linear displacements, with potential for scalability and use in diverse applications such as transmission clutches and engine pistons.
Implementation Method 1
two magnets configured to produce a magnetic flux density and magnetic field in a region between the two magnets that is substantially uniform
Implementation Method 2
a magnetic field sensor at a fixed location, or vice versa, to detect the magnetic field produced by the attached magnet
Data Source
AI summary
In a position sensor, two field sensors are placed along a line parallel to the movement to be detected. Two magnets are placed at an angle to each other to generate a magnetic field such that their position is a linear or approximately linear function of the difference between the outputs of the sensors.