Rotation-Angle Detection Device With Dummy MR Elements
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Solution Overview
Problem
Magnetic sensors for rotation-angle detection face inefficiencies in canceling waveform distortions due to irregular magnetism collection effects and spatial distortions of magnetic flux densities, leading to imbalances in signal cancellation between paired MR elements.
Innovation Solution
A rotation-angle detection device with a detection track comprising first and second magnetic resistance element groups arranged at specific pitches, accompanied by dummy elements to ensure equivalent magnetism collection effects and uniform spatial distribution of magnetic flux densities, thereby improving distortion cancellation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MR elements are arranged according to the waveform-distortion cancellation rule (at non-equidistant pitches), then harmonic distortion cancellation is improved, but magnetism collection uniformity deteriorates
Solution Approach 1:
The detection track is segmented into multiple MR element groups (first detection element group, second detection element group, and dummy magnetic resistance elements) arranged at different positions. Each segment serves a specific function: some segments detect magnetic flux while others serve as references or dummies to maintain uniform spacing. This segmentation allows the system to achieve both distortion cancellation through differential processing and uniform magnetism collection through equidistant physical arrangement.
Solution Approach 2:
Different regions of the detection track are assigned different functions with locally optimized properties. The first and second detection element groups are positioned to detect specific magnetic flux components, while dummy elements are placed to maintain uniform spacing. This local differentiation enables each element to contribute optimally to either distortion cancellation or magnetism collection uniformity, resolving the contradiction between these two requirements.
2Measurement precision
If MR elements are arranged at non-equidistant pitches to cancel third and fifth harmonics, then waveform distortion cancellation is improved, but spatial distribution uniformity deteriorates
Solution Approach 1:
The detection track is designed with equipotential characteristics by arranging all magnetic resistance elements (including dummy elements) at equidistant intervals. This creates a uniform potential distribution across the detection track, ensuring that all elements experience similar magnetic flux conditions. The equipotential arrangement maintains spatial distribution uniformity while the differential processing of specific element groups achieves waveform distortion cancellation.
Solution Approach 2:
The invention changes the arrangement parameter from non-equidistant to equidistant spacing, fundamentally altering the spatial distribution characteristic. By maintaining uniform spacing while using differential processing of specific element groups, the system achieves distortion cancellation without compromising spatial distribution uniformity, thus resolving the contradiction between these two parameters.
3Measurement precision
If paired MR elements are arranged at different positions for distortion cancellation, then harmonic component cancellation is improved, but signal balance deteriorates
Solution Approach 1:
The detection track uses dummy magnetic resistance elements as copies or references for the actual detection elements. These dummy elements replicate the physical structure and spacing characteristics but serve as reference points for differential processing. By comparing signals from actual detection elements with their dummy references, the system achieves harmonic cancellation while maintaining signal balance, as the copying approach ensures consistent magnetic flux collection characteristics.
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 solution enhances the efficiency of canceling waveform distortions by ensuring equivalent magnetism collection effects and uniform spatial distributions, achieving a distortion cancellation rate of 90% or higher, which is practically required for accurate rotation-angle detection.
Implementation Method 1
Magnetic resistance elements (MR elements) such as AMR elements are used for the magnetic sensor, and the magnetic sensor uses properties of the AMR elements that electric resistance changes in proportion to the change in a magnetic field
Implementation Method 2
a magnetic field generated by a multi-pole magnetic pattern on the rotary drum having N and S poles which are provided on an outer circumference and on which magnetization alternately occurs at a magnetization pitch λ
Data Source
AI summary
A detection track includes a first detection element group that includes a plurality of first magnetic resistance elements arranged at a pitch λ/(2n) when an order to cancel target harmonic components among a plurality of harmonic components superimposed on a fundamental component of a detection signal for multi-pole magnetic pattern is assumed as n, and a second detection element group that includes a plurality of second magnetic resistance elements arranged at the pitch λ/(2n), a plurality of first dummy magnetic resistance elements arranged among the first magnetic resistance elements, and a plurality of second dummy magnetic resistance elements arranged among the second magnetic resistance elements. Pitches between adjacent magnetic resistance elements among the first magnetic resistance elements and the first dummy magnetic resistance element are equivalent to one another, and pitches between adjacent magnetic resistance elements among the second magnetic resistance elements and the second dummy magnetic resistance element are equivalent to one another.