Inductive Encoder Winding Layout for Harmonic Error Reduction
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Solution Overview
Problem
Inductive position encoders face challenges in achieving a combination of compact size, high resolution, accuracy, low cost, robustness to contamination, and robustness to misalignments while providing spatially filtered detector signals to reduce harmonic errors.
Innovation Solution
The electronic position encoder employs a scale with a periodic pattern of signal modulating elements and a detector portion with sensing elements arranged in specific configurations to generate and respond to changing magnetic flux, featuring shifted sensing element effective areas and spatial filtering to suppress unwanted harmonic components, thereby improving accuracy and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inductive encoder configurations are used, then manufacturing simplicity is maintained, but measurement precision and robustness to misalignments deteriorate due to harmonic errors
Solution Approach 1:
The sensing winding is divided into multiple discrete sensing elements (first sensing element, second sensing element, third sensing element) with different orientations. Each element responds to different components of the magnetic flux, and their signals are combined to cancel harmonic errors. This segmentation enables precise measurement while maintaining a relatively simple overall structure.
Solution Approach 2:
Different sensing elements are assigned different orientations and positions within the detector portion. The first sensing element has a specific orientation, while the second and third sensing elements have orientations shifted by predetermined angles. This local differentiation in quality (orientation) allows each element to capture specific magnetic flux components, improving measurement precision through selective sensing.
2Volume of moving object
If compact encoder size is achieved, then device dimensions are reduced, but measurement accuracy deteriorates due to limited space for sensing elements
Solution Approach 1:
The sensing elements are arranged in a three-dimensional configuration within the detector portion, with orientations distributed in different spatial dimensions. The second and third sensing elements are oriented at predetermined angles relative to the first, utilizing angular dimensionality to maximize sensing capability within a compact volume. This dimensional arrangement enables high measurement precision without increasing the overall detector volume.
3Measurement precision
If spatial filtering is implemented to reduce harmonic errors, then measurement accuracy is improved, but device complexity increases due to additional sensing elements and signal processing
Solution Approach 1:
Multiple sensing elements with different orientations are merged into a single detector portion that processes signals collectively. The signals from the first, second, and third sensing elements are combined through signal processing to achieve spatial filtering and harmonic error reduction. This merging approach consolidates the filtering function within the detector structure, improving measurement precision without proportionally increasing overall device complexity.
4Reliability
If robustness to misalignments is enhanced through multiple sensing elements, then reliability improves, but manufacturing cost increases
Solution Approach 1:
The detector portion with multiple sensing elements serves multiple functions simultaneously: it detects magnetic flux components in different orientations, performs spatial filtering to reduce harmonic errors, and provides robustness to misalignments through redundant sensing. This multi-functionality is achieved within a single integrated detector structure, improving reliability without requiring separate systems for each function, thereby controlling manufacturing costs.
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 encoder's ability to accurately measure relative positions with reduced harmonic errors, offering improved spatial filtering and robustness against misalignments while maintaining economical fabrication and low costs.
Implementation Method 1
The field generating coil is configured to generate a changing magnetic flux in the interior area in response to a coil drive signal
Implementation Method 2
Each respective set of sensing elements is configured to provide detector signals which respond to a local effect on the changing magnetic flux
Data Source
AI summary
An inductive position encoder includes a scale, detector, and signal processor. The scale includes a periodic pattern of signal modulating elements (SME) arranged along a measuring axis (MA) with spatial wavelength W1. The detector comprises sensing elements and a field generating coil that generates changing magnetic flux. The sensing elements comprise conductive loops that provide detector signals responsive to a local effect on the magnetic flux provided by adjacent SME's. The conductive loops have an average MA dimension that spatially filters a 3rd spatial harmonic signal component and are located along the MA according to an “inter-loop” shift relationship wherein first and second equal numbers of positive and negative polarity loops, are shifted in opposite directions by W1/4K (K=3, 5, 7, 9). Third and Kth spatial harmonic components are both reduced in the detector signals while using a novel “layout friendly” loop arrangement to solve longstanding detrimental layout problems.