Multipole Magnetic Sensor Layout for Stray Field Compensation
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Solution Overview
Problem
Sensor devices are adversely affected by magnetic stray fields, leading to inaccurate measurements in environments where such fields are present, particularly in applications like EPS systems.
Innovation Solution
A sensor device design incorporating a multipole magnet and stator pairs with magnetic flux concentrators and magnetic field sensors arranged to compensate for the influence of rotation-independent magnetic stray fields through difference or summation of sensor signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic field sensors are used to detect the magnetic field induced by the multipole magnet, then the sensor device can measure rotation or position, but the measurements are corrupted by magnetic stray fields present in the environment
Solution Approach 1:
The sensor device is divided into multiple stator pairs (first stator pair and second stator pair) with corresponding magnetic field sensors. Each stator pair independently detects the magnetic field, and their signals are combined through difference formation or summation to cancel out the influence of magnetic stray fields while preserving the rotation-dependent signal.
Solution Approach 2:
The magnetic stray field, which was previously a harmful factor corrupting measurements, is converted into a beneficial element for compensation. By arranging multiple sensors and stator pairs symmetrically and combining their signals through difference formation or summation, the stray field influence appears equally in all sensor signals and can be mathematically eliminated, turning the harmful universal interference into a cancelable common-mode signal.
2Reliability
If multiple stator pairs and magnetic field sensors are added to compensate for magnetic stray fields, then measurement reliability improves, but device complexity increases
Solution Approach 1:
Multiple stator pairs and magnetic field sensors are merged into a unified sensor device structure where the first stator pair and second stator pair share common components and spatial arrangement. The magnetic flux concentrator and magnetic field sensors serve dual purposes by participating in both the measurement of rotation-dependent magnetic fields and the compensation of rotation-independent magnetic stray fields, thereby improving reliability without proportionally increasing complexity.
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 device provides measurements that are independent of magnetic stray fields, ensuring accurate and reliable operation even in environments with magnetic interference.
Implementation Method 1
a multipole magnet, which is rotatable relative to the two stator pairs, wherein a magnetic field is induced as a result of the rotation of the multipole magnet relative to the stator pairs
Implementation Method 2
a magnetic flux concentrator configured to concentrate the induced magnetic field at the location of the first magnetic field sensor and at the location of the second magnetic field sensor
Implementation Method 3
a first magnetic field sensor configured to output a first sensor signal; a second magnetic field sensor configured to output a second sensor signal
Implementation Method 4
The magnetic flux concentrator and the two magnetic field sensors are arranged in such a way that an influence of a rotation-independent magnetic stray field on the two sensor signals is compensated for upon difference formation or summation applied to the two sensor signals
Data Source
AI summary
A sensor device includes a first stator pair, consisting of a first and second ferromagnetic stators and a second stator pair, consisting of the second ferromagnetic stator and a third ferromagnetic stator. The sensor device includes a multipole magnet, rotatable relative to the two stator pairs. A magnetic field is induced as a result of the rotation. The sensor device includes first and second magnetic field sensors configured to output first and second sensor signals, respectively. The sensor device includes a magnetic flux concentrator configured to concentrate the induced magnetic field at the location of the first magnetic field sensor and at the location of the second magnetic field sensor. The magnetic flux concentrator and the two magnetic field sensors are arranged such that an influence of a rotation-independent magnetic stray field on the sensor signals is compensated for upon difference formation or summation applied to the sensor signals.