Rotating Field Sensor Harmonic Reduction via MR Magnetization Angles
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Solution Overview
Problem
Rotating field sensors face errors in detecting angles due to harmonic components in the output signals of magnetoresistive elements, which are not easily corrected and require complex configurations, especially when magnets are arrayed with arbitrary pitches.
Innovation Solution
A rotating field sensor design incorporating a first and second detection circuit with magnetoresistive elements connected in series, where the magnetization directions of pairs of elements form a predetermined relative angle other than 0° and 180°, allowing for the reduction of harmonic components by combining their potential difference harmonic components, thereby simplifying the configuration and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correction sensing elements are added to eliminate error signals, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent changes the magnetization direction parameter of the pinned layers in magnetoresistive elements. By setting specific relative angles (other than 0° and 180°) between pinned layer magnetization directions, the sensor achieves error signal elimination without requiring additional correction elements, thus improving angle detection accuracy while maintaining simple structure
Solution Approach 2:
Instead of adding correction elements to eliminate errors (conventional approach), the patent inverts the approach by configuring the magnetization directions of existing elements to inherently produce complementary error signals that cancel each other out. This eliminates the need for additional correction sensing elements while achieving the same error reduction effect
2Measurement precision
If multiple magnetoresistive elements with specific arrangements are used to reduce harmonic components, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent changes the magnetization direction parameter of pinned layers to achieve error reduction. By configuring pinned layers at specific relative angles, the sensor reduces harmonic components and improves angle detection accuracy without requiring complex spatial arrangements or precise positioning of multiple elements, thereby maintaining ease of manufacture
3Measurement precision
If magnetoresistive elements are arranged according to specific pitch requirements, then measurement precision is improved, but adaptability deteriorates
Solution Approach 1:
The patent changes the magnetization direction parameter rather than relying on specific spatial arrangements. This approach makes the sensor adaptable to magnets arrayed with arbitrary pitches, as the error reduction mechanism depends on magnetization angles rather than physical distances or positions, thereby improving both angle detection accuracy and adaptability
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 design effectively reduces the harmonic components in the potential difference across magnetoresistive elements, leading to more accurate angle detection with a simpler configuration, reducing the number of elements needed and minimizing temperature-based errors.
Implementation Method 1
magnetoresistive elements (hereinafter, also referred to as MR elements) serving as magnetic detection elements
Data Source
Figure 1~2
Figure 3
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AI summary
A rotating field sensor (5) includes a first detection circuit (21) that outputs a first signal (S1) indicating the intensity of a component of a rotating magnetic field (hollow arrows) in a first direction, a second detection circuit (22) that outputs a second signal (S2) indicating the intensity of a component of the rotating magnetic field in a second direction, and an arithmetic circuit (13) that calculates a detected angle value (θS) based on the first and second signals. Each of the first and second detection circuits includes at least one MR element row (R11...R24). Each MR element row is composed of a plurality of MR elements (R111...R242) connected in series. Each MR element has a magnetization pinned layer (filled arrows). The plurality of MR elements forming each MR element row include one or more pairs of MR elements. In each pair of MR elements, the magnetization directions of the magnetization pinned layers in the two MR elements making up the pair form a predetermined relative angle other than 0° and 180°.