Magnetic Sensor Offset for Axial Position Detection
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Solution Overview
Problem
Magnetic position sensor systems face challenges in accurately determining the axial and angular positions of a magnet without physical contact, especially in environments with external disturbances and temperature variations, while maintaining robustness and efficiency.
Innovation Solution
A magnetic sensor system comprising a magnet and a sensor device offset from the axis, using specific magnetic field components and gradients to determine axial and angular positions through processing circuits that calculate sums and thresholds, allowing for robust position detection regardless of the magnet's rotation or angular orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a magnetic sensor system uses a simple or cheap magnetic structure, then manufacturing cost is reduced, but measurement precision and robustness against external disturbances deteriorate
Solution Approach 1:
The patent applies asymmetry by positioning the magnetic sensor device at a non-zero distance (offset) from the magnet's rotation axis. This asymmetric configuration creates a unique magnetic field signature that enables accurate position determination while using simple magnet structures. The offset position allows the sensor to detect both radial and axial magnetic field components, providing sufficient information for precise measurement without requiring complex magnetic structures.
Solution Approach 2:
The patent utilizes another dimension by measuring magnetic field components in multiple spatial dimensions. The sensor device measures both radial (Br) and axial (Bz) magnetic field components, and the method involves calculating derivatives with respect to different spatial coordinates. This multi-dimensional measurement approach enables accurate position determination using simple magnetic structures by exploiting the spatial variation of the magnetic field.
2Reliability
If the sensor device is located at a non-zero distance from the axis, then robustness against angular position variations is improved, but measurement precision deteriorates due to weaker magnetic field signals
Solution Approach 1:
The patent applies parameter changes by utilizing derivatives of magnetic field components with respect to spatial coordinates. Instead of directly using the magnetic field components Br and Bz, the method calculates partial derivatives (∂Br/∂r, ∂Br/∂z, ∂Bz/∂r, ∂Bz/∂z). This transformation of parameters enhances the signal characteristics and enables accurate position determination even when the sensor is offset from the axis, maintaining both robustness and precision.
3Adaptability or versatility
If the system measures both axial and angular positions, then versatility is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing a single sensor system that can determine both axial position (z) and angular position (φ) of the magnet. The same offset-positioned magnetic sensor device and processing circuit that measure radial and axial magnetic field components can compute both position types by applying different calculations to the same raw measurements. This multi-functional approach enables the system to provide comprehensive position information without requiring separate sensor systems for each measurement type.
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 effectively determines axial and angular positions with high accuracy and robustness against external disturbances and temperature variations, improving reliability and efficiency in applications like push-button systems.
Implementation Method 1
the magnet generates a magnetic field extending into a surrounding space
Data Source
Figure 1~1(j)
Figure 1(k)~1(n)
Figure 2
AI summary
A magnetic sensor system comprising a magnet and a sensor device. The magnet has a shape and is movable along an axis (A) between a first position (z1) and a second position (z2), and is optionally also rotatable about this axis. The magnetic sensor device comprises a plurality of magnetic sensitive elements for measuring at least two orthogonal magnetic field components or at least two orthogonal magnetic field gradients, and a processing circuit for determining an axial position of the magnet or whether the magnet is located in said first or second position (z1, z2) based on the first and second magnetic field components or gradients, and optionally also for estimating or calculating an angular position of the magnet. A method of determining said axial and/or angular position. A magnetic sensor device.