Radially Magnetized Isotropic Multi-Pole Magnet for Angular Position Sensing
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Solution Overview
Problem
Existing angular position sensor systems are not robust enough against position errors due to axial distance and radial offset variations, and they degrade over time due to mechanical drift and vibrations, leading to reduced accuracy.
Innovation Solution
An angular position sensor system utilizing a multi-pole ring magnet with an isotropic magnetic material, where the magnetic field is magnetized such that it creates a remanent magnetic field with constant in-plane field gradients, reducing sensitivity to axial distance and radial offset errors, and is designed to maintain accuracy despite mechanical drift and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anisotropic permanent magnets with vertically magnetized surfaces are used, then the magnetic field strength is sufficient, but the sensor system becomes highly sensitive to axial distance and radial offset position errors
Solution Approach 1:
The patent changes the magnetization parameters from vertical (axial) magnetization of anisotropic magnets to radial magnetization of isotropic magnets. This parameter change transforms the magnetic field distribution characteristics, creating constant in-plane field gradients that are independent of axial distance and radial offset, thereby resolving the contradiction between robustness against position errors and measurement precision
Solution Approach 2:
The patent applies different magnetization directions at different locations around the magnet circumference. Each radial segment of the magnet is magnetized in the radial direction, creating localized magnetic field contributions that collectively produce the desired constant gradient field pattern, making the sensor response uniform across different positions
2Reliability
If complex algorithms or higher number of sensor elements are used to improve robustness, then position error compensation improves, but device complexity increases
Solution Approach 1:
The patent extracts the position error compensation function from the algorithmic processing domain and transfers it to the magnetic field generation domain. By designing the magnet geometry and magnetization pattern to inherently produce constant field gradients, the system eliminates the need for complex position error compensation algorithms, reducing device complexity while maintaining robustness
3Measurement precision
If mechanically tighter tolerances are applied to reduce position errors, then angular position accuracy improves, but manufacturing cost and difficulty increase
Solution Approach 1:
The patent changes the magnetic field gradient parameters from position-dependent (conventional magnets) to position-independent (radially magnetized isotropic magnets). This parameter change makes the sensor system's measurement precision independent of mechanical alignment tolerances, allowing for easier manufacturing and assembly while maintaining high angular position 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 sensor system achieves enhanced robustness and accuracy by maintaining a consistent magnetic field orientation, reducing position errors and mechanical drift impacts, and providing improved performance in the presence of vibrations.
Implementation Method 1
the magnet creates a remanent magnetic field which, for each point of an imaginary circle located in a plane perpendicular to said axis
Implementation Method 2
a sensor device for measuring a magnetic field created by the permanent magnet and/or for measuring values derived therefrom
Data Source
Figure 1(a)~1(b)
Figure 2(a)~3
Figure 4(a)~5(c)
AI summary
A permanent magnet (101) in the form of a multi-pole magnet, comprising an isotropic magnetic material, having a central axis (A), magnetised such that the magnetic field, considered on a virtual circle (c) lies substantially in a virtual plane (ε) tangential to the circle, and rotates inside that virtual plane, depending on the position on the circle. A method (1300) of producing a magnet comprising: a) providing a shaped body comprising an isotropic magnetic material; b) providing at least four electrical conductor segments; c) simultaneously make currents flow in each conductor segment. A magnet made in this way. Use of such a magnet for angular position sensing. An angular position sensor system (100) comprising such a magnet.