Gradiometric Angle Sensors Reduce Magnet Cost
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Solution Overview
Problem
Conventional magnetic field angle sensors face challenges such as high cost, sensitivity to external magnetic fields, and reduced accuracy due to assembly tolerances, particularly when using stronger magnets and Hall-effect sensor elements, which limits their applicability in cost-sensitive and robustness-critical applications.
Innovation Solution
A magnetic field angle sensor system with at least three sensor elements arranged around the rotation axis, configured to sense gradients of magnetic field components perpendicular to the axis, using a die with circuitry to determine the rotational position through linear combinations of these gradients, thereby reducing the need for strong magnets and enhancing robustness against external disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If stronger magnets are used to improve magnetic field strength, then magnetic field intensity is improved, but cost increases
Solution Approach 1:
The patent changes the measurement parameter from absolute magnetic field strength to magnetic field gradient. By measuring the gradient (rate of change) of the magnetic field rather than the field strength itself, the system achieves accurate angle sensing with weaker magnets, thereby reducing cost while maintaining performance.
Solution Approach 2:
The patent uses multiple sensor elements (at least three) arranged around the rotation axis to measure different components of the magnetic field gradient. This segmentation of the measurement function across multiple elements enables gradient measurement that is more robust to external disturbances and allows use of weaker magnets.
2Measurement precision
If Hall-effect sensor elements are used to improve linearity, then measurement linearity is improved, but cost increases
Solution Approach 1:
The patent changes from measuring absolute field values to measuring field gradients. This parameter change reduces the linearity requirements for sensor elements because gradient measurements are less sensitive to non-linearities in the sensor response, enabling use of lower-cost sensor technologies.
Solution Approach 2:
The patent uses multiple copies of sensor elements arranged in a gradiometric configuration. By using at least three sensor elements to measure different gradient components and combining their signals, the system achieves robust angle measurement that is less dependent on individual element linearity.
3Adaptability or versatility
If off-axis sensor arrangement is used to accommodate shaft constraints, then adaptability is improved, but sensitivity to external magnetic fields increases
Solution Approach 1:
The patent segments the magnetic field measurement into multiple gradient components measured by separate sensor elements. By measuring gradients in different directions and combining them through linear combinations, the system achieves insensitivity to uniform external magnetic fields while maintaining adaptability for off-axis mounting.
Solution Approach 2:
The patent converts the challenge of off-axis positioning into a benefit by designing a gradiometric measurement system that is inherently insensitive to uniform external fields. The gradient measurement approach naturally rejects uniform field disturbances, turning the off-axis constraint into an opportunity for improved robustness.
4Reliability
If gradiometric measurement with multiple sensor elements is used to reduce sensitivity to external fields, then robustness is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple sensor element measurements into a unified angle determination through linear combinations of gradient components. By integrating the signals from multiple elements and processing them through defined linear combinations, the system achieves robustness against external disturbances while managing complexity through systematic signal processing.
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 provides accurate and robust determination of rotational position with reduced sensitivity to external magnetic fields and assembly tolerances, achieving cost-effectiveness and improved performance by utilizing magneto-resistive or Hall-effect sensor elements in a gradiometric configuration.
Implementation Method 1
at least three magnetic field sensor elements arranged on a first surface of the die around the projection of the rotation axis, the at least three magnetic field sensor elements configured to sense at least two gradients of a magnetic field induced by the magnetic field source
Implementation Method 2
circuitry configured to determine the rotational position of the magnetic field source by determining at least one linear combination of the at least two gradients and deriving the rotational position from the at least one linear combination
Data Source
AI summary
Embodiments relate to magnetic field sensors, such as gradiometric magnetic field angle sensors with generally on-axis arrangements of sensor elements relative to a rotation axis of a magnet. In one embodiment, an angle sensor is arranged on-axis with respect to the rotation axis of a magnet that generates a magnetic field that can be detected by the angle sensor and analyzed to determine an angular position of the magnet. The sensor can comprise a plurality of sensor elements, such as two sensor elements, arranged on a substrate or die in a sensor package. As it rotates, the magnet generates a magnetic field, such as an inhomogenous magnetic field having a component perpendicular to the rotation axis and acting on the angle sensor. The plurality of sensor elements can detect this and other components, for example as a gradiometric sensor in which each element senses at least one component at its respective location, and the signals from the elements are compared to estimate or determine an angular position or degree of movement of the magnet.