TMR Position Sensor Harmonic Cancellation
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Solution Overview
Problem
Conventional position detecting devices using AMR elements face challenges with low resistance change rates under magnetic fields, leading to signal distortion and reduced accuracy due to the large size of these elements, which complicates the arrangement of multiple detecting elements needed to cancel harmonics and maintain precise position detection.
Innovation Solution
The use of TMR elements with a specific pattern arrangement and bias magnetic field application to reduce odd-order harmonics and improve signal linearity, allowing for accurate position detection with a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AMR elements are used as magnetism detecting elements, then position detection can be performed, but the resistance change rate with respect to magnetic field is small and the element size is large, making it difficult to arrange multiple detecting elements compactly to cancel harmonics
Solution Approach 1:
The patent changes the fundamental detection mechanism from AMR (anisotropic magnetoresistance) to TMR (tunnel magnetoresistance) elements. This parameter change in the detection technology provides a resistance change rate that is 10 times or more larger than AMR elements, enabling compact arrangement of multiple detecting elements while maintaining position detection accuracy and facilitating harmonic cancellation.
Solution Approach 2:
The patent arranges multiple TMR detecting elements in specific spatial patterns (such as 2x2 matrices or linear arrangements) to detect and cancel odd-order harmonics. By utilizing spatial dimensionality and specific geometric arrangements, the system achieves harmonic cancellation while maintaining compact size, resolving the contradiction between detection accuracy and arrangement complexity.
2Reliability
If multiple magnetism detecting elements are arranged to cancel odd-order harmonics, then signal linearity improves, but the element size and arrangement complexity increase
Solution Approach 1:
The transition to TMR elements changes the resistance change rate parameter, allowing multiple detecting elements to be arranged in compact patterns. This enables effective harmonic cancellation for improved signal linearity without proportionally increasing device complexity, as the TMR elements themselves are more space-efficient than AMR elements.
Solution Approach 2:
The patent segments the detection function into multiple TMR elements arranged in specific patterns (such as 2x2 matrices or linear arrangements spaced at specific intervals). Each element contributes to detecting and canceling specific odd-order harmonics, achieving signal linearity improvement through functional segmentation while maintaining compact overall device size.
3Measurement precision
If TMR elements are used with specific pattern arrangement, then odd-order harmonics are reduced and signal linearity improves, but the device structure becomes more complex
Solution Approach 1:
The detection function is segmented into multiple TMR elements arranged in specific patterns such as 2x2 matrices or linear arrangements. Each segment detects specific harmonic components, and through differential connection, odd-order harmonics are canceled. This segmentation achieves signal linearity improvement while the modular pattern arrangement keeps the overall structural complexity manageable.
Solution Approach 2:
Multiple TMR detecting elements are merged into integrated detection units with specific spatial arrangements. The elements are connected in differential configurations that combine their output signals to cancel odd-order harmonics. This merging approach achieves signal linearity improvement while consolidating the complex arrangement into unified detection modules.
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 approach enables accurate position detection with reduced signal distortions and improved sensitivity, enhancing the precision and efficiency of position detection in position detecting devices.
Implementation Method 1
a magnetism detecting element (21) configured to detect a leakage magnetism from the scale (11) and output a signal corresponding to a recording signal
Implementation Method 2
bias magnetic field generation sections (31, 32) arranged near the magnetism detecting element (21)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A magnetism detecting element detects a leakage magnetism from a scale, on which a magnetic signal with a constant period is recorded, and a relative position between the scale and the magnetism detecting element is detected. The magnetism detecting elements are arranged, along a detection direction of the magnetic signal relative to the scale, in a pattern with a pitch of 1/2n (n is a prime number of 3 or more) of a wavelength λ' of a signal output by the element. Furthermore, as the pattern for cancelling m odd-order harmonics, the m-th power of 2 magnetism detecting elements are arranged within a range in which a pitch distance L of the magnetism detecting element farthest in the detection direction is expressed by L=(λ'/2)×(1/3+1/5+1/7+... 1/(2m+1)).