Multi-Gradiometer Magnetic Sensor for Angular Position
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Solution Overview
Problem
Magnetic sensors used to determine the angular position of rotatable objects face errors due to disturbances in the magnetic field, and increasing the size of the sensor to enhance accuracy is costly and space-consuming.
Innovation Solution
A magnetic sensor arrangement with multiple gradiometers positioned on axes perpendicular to the rotational axis, with sensing elements spaced far apart to minimize disturbance detection, maintaining a compact size by offsetting the gradiometer centers from the rotational axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor size is increased to enhance accuracy, then measurement precision is improved, but device complexity and space requirements increase
Solution Approach 1:
The magnetic sensor is divided into multiple gradiometer units, each with its own sensing elements arranged in specific patterns. This segmentation allows the system to achieve high measurement precision through multiple measurements and signal processing, rather than requiring a single large sensor element.
Solution Approach 2:
The patent transitions from a single-plane sensing arrangement to a three-dimensional configuration with sensing elements positioned at different heights (first plane and second plane). This dimensional expansion enables the gradiometers to measure magnetic field gradients more accurately without increasing the overall sensor footprint.
2Measurement precision
If sensing elements are positioned closer to the rotational axis, then the sensor can detect smaller magnetic field variations, but the sensor becomes more susceptible to disturbances
Solution Approach 1:
The patent converts the harmful effect of magnetic field disturbances into a useful measurement. By using gradiometers that measure the gradient (rate of change) of the magnetic field rather than the absolute field strength, the system can distinguish between actual angular position information and disturbance signals. The gradient measurement inherently rejects uniform field disturbances while preserving the spatial variation information needed for accurate angle determination.
Solution Approach 2:
The gradiometer configuration acts as an intermediary between the magnetic field source and the measurement system. By measuring the spatial gradient of the magnetic field rather than the field directly, the system mediates the measurement process to filter out disturbances while preserving the angular position signal.
3Reliability
If multiple gradiometers are used to improve measurement accuracy, then reliability is enhanced, but device complexity increases
Solution Approach 1:
Multiple gradiometers are merged into a single integrated sensor unit with a unified structure. The first and second gradiometers share common elements and are positioned in a coordinated three-dimensional arrangement, allowing them to function as an integrated system rather than separate independent sensors, thus reducing overall device complexity.
Solution Approach 2:
The gradiometer assembly serves multiple functions simultaneously: it measures magnetic field gradients in different directions, determines angular position, and rejects magnetic field disturbances. This multi-functionality is achieved through the coordinated arrangement of sensing elements in multiple planes, allowing a single device structure to perform several measurement tasks.
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 configuration enhances the accuracy of angular position determination while maintaining a small sensor size, reducing the likelihood of sensing disturbances and avoiding system errors.
Implementation Method 1
the first set of sensing elements and the second set of sensing elements are configured to sense a set of magnetic field components, that are perpendicular to the center of the rotational axis; and a digital signal processor that may obtain, via the first gradiometer and the second gradiometer, the set of magnetic field components, wherein the set of magnetic field components are measured from a magnetic field generated by a magnet configured to co-rotate with the rotatable object
Data Source
AI summary
An example device includes a first gradiometer that includes a first set of sensing elements aligned along a first axis, a second gradiometer that includes a second set of sensing elements aligned along a second axis, and a controller. The first set of sensing elements and the second set of sensing elements may be configured to sense a set of magnetic field components that are perpendicular to the rotational axis, wherein the first axis is in a first plane and the second axis is in a second plane, and the first plane and the second plane may be perpendicular to a rotational axis of a rotatable object. The controller may obtain, via the first gradiometer and the second gradiometer, the set of components of the magnetic field. The controller may then determine, based on obtaining the set of components of the magnetic field, the angular position of the rotatable object.