Magnetic Angular Position Sensor with Single-Point Dual-Axis Probe
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Solution Overview
Problem
Existing magnetic rotary position sensors for 360° angles, such as those used in automobile steering columns, face measurement errors due to the placement of multiple probes and increased costs associated with spatially offset integrated circuits, and are limited by the geometry of the steering column, which prevents the magnetosensitive element from being positioned on the axis of rotation.
Innovation Solution
Measuring both radial and tangential or axial components of the magnetic field at a single point outside the axis of rotation of a diametrically magnetized ring or disc magnet, using a pair of magnetic field components out of phase by 90 degrees to decode the angle, and employing a single integrated circuit with a magnetic flux concentrator to normalize and process these signals, thereby reducing costs and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two magnetosensitive probes are used to measure radial and tangential magnetic field components, then angular position can be determined, but measurement errors occur due to bad placement of probes relative to each other
Solution Approach 1:
The patent combines both radial and tangential magnetic field component measurements into a single magnetosensitive probe located on the rotation axis. The probe simultaneously detects Bx (radial component) and By (tangential component) through its two orthogonal sensitive axes, eliminating placement errors between separate probes while maintaining angular position measurement accuracy.
Solution Approach 2:
The patent transitions from measuring only radial magnetic field components (2D approach with probes at 90°) to measuring both radial and tangential components (3D approach with dual-axis sensitivity) at a single point on the rotation axis. This dimensional enhancement allows accurate angular determination without multiple probe placements.
2Measurement precision
If two integrated circuits are used spatially offset by 90° to measure magnetic field components, then angular position can be detected, but the printed circuit surface area increases and connection数量 increases, raising production cost
Solution Approach 1:
The patent merges the functions of two separate integrated circuits into a single integrated circuit located on the rotation axis. This single circuit incorporates both orthogonal magnetosensitive probes and performs both radial and tangential magnetic field component measurements simultaneously, reducing printed circuit surface area and connection数量 while maintaining angular position detection accuracy.
Solution Approach 2:
The single integrated circuit is designed with multi-functionality, incorporating both radial and tangential magnetic field sensing capabilities within one device. This universal approach eliminates the need for separate circuits positioned at 90° offsets, simplifying the overall sensor structure and reducing manufacturing complexity.
3Reliability
If the magnetosensitive element is positioned on the axis of rotation to measure magnetic field components, then measurement reliability improves, but the steering column geometry prevents such positioning
Solution Approach 1:
The patent merges radial and tangential magnetic field component measurements into a single probe on the rotation axis, enabling reliable angular position measurement. This configuration is specifically adapted for through-shaft systems like steering columns, where the magnet rotates on the shaft axis and the probe measures field components at a point outside this axis, accommodating the geometrical constraints while maintaining measurement reliability.
4Ease of manufacture
If a single integrated circuit is used to measure both magnetic field components, then production cost decreases and reliability increases, but the circuit must process and normalize two different sinusoidal signals
Solution Approach 1:
The single integrated circuit performs self-service by automatically normalizing the two different sinusoidal signals (radial and tangential components) internally. The circuit includes signal processing capabilities that handle the different amplitudes and phases of the two components, performing normalization and decoding operations within the same device that generates the quadrature signals, thereby simplifying external circuitry while managing the processing complexity internally.
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 reduces the cost and increases the reliability of the sensor while adapting to different geometrical configurations, including through-axis devices, by using a single integrated circuit and compensating for non-linearity errors in the magnetic field curvature, allowing accurate angular position measurement without mechanical contact or wear.
Implementation Method 1
measuring both radial and tangential or axial components of the magnetic field at a single point outside the axis of rotation of a diametrically magnetized ring or disc magnet
Implementation Method 2
The magnetic field bends near the ferromagnetic disc (which has a large relative permeability). The magnetic field lines are perpendicular to the surface of the magnetic flux concentrator and they pass through the Hall elements, thus making it possible to measure the two magnetic field components in the plane of the probe. In addition, the magnetic field measured by the Hall elements is amplified, because the field lines are concentrated close to the ferromagnetic disc.
Implementation Method 3
The Hall elements on each axis (X and Y or X and Z) are connected to a signal processing circuit which outputs the voltage difference of the two Hall elements (which eliminates the axial component of the magnetic field)
Data Source
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AI summary
The present invention relates to an angular position sensor comprising a moving element consisting of at least one substantially cylindrical permanent magnet (1) rotating about its axis, at least two magnetosensitive elements (2, 3) and at least one processing circuit (4) delivering a signal as a function of the absolute position of the moving element, characterized in that the magnetosensitive elements (2, 3) are located substantially at the same point and in that they measure the tangential component of the magnetic field and the radial and/or axial component of the magnetic field to provide 2 sinusoidal signals substantially out of phase by 90°.