Inductive Encoder Coil End Gradient and Shielding Design
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Solution Overview
Problem
Existing inductive position encoder systems face limitations in achieving a combination of high signal strength, compact size, high resolution, cost-effectiveness, and robustness to misalignment and contamination, particularly due to issues like 'end effects' that affect measurement accuracy.
Innovation Solution
The electronic position encoder incorporates a multi-layer circuit element with a field generating coil configuration and sensing elements, featuring end gradient arrangements that reduce field strength near the ends of the measurement axis, and a conductive shield region to mitigate periodic errors and misalignment sensitivity, using Type A and Type B end gradient configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional field generating coil configurations are used, then signal strength is maintained, but end effects cause measurement errors and reduce accuracy
Solution Approach 1:
The patent applies local quality by implementing end gradient arrangements that create non-uniform field strength distribution along the measurement axis. The field generating coil configuration includes first and second elongated portions with different dimensional characteristics at different locations, causing the magnetic flux to vary locally along the x-axis direction. This local variation in field quality compensates for end effects and improves measurement accuracy at the ends of the measurement range.
Solution Approach 2:
The patent employs asymmetry through the field generating coil configuration where the first and second elongated portions have different dimensions and are positioned asymmetrically relative to the signal modulating elements. The first elongated portion has a first dimension and the second elongated portion has a second dimension, creating an asymmetric magnetic flux distribution that counteracts end effects and improves measurement precision.
2Volume of moving object
If the detector portion size is reduced for compactness, then device size decreases, but misalignment sensitivity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the dimensional parameters of the field generating coil configuration and the spacing between the detector portion and the signal modulating elements. By carefully selecting the dimensions of the elongated portions and the gap distance, the system achieves compactness while maintaining robustness to misalignment through appropriate parameter selection.
3Measurement precision
If traditional coil configurations are used, then manufacturing is simpler, but signal strength and resolution are limited
Solution Approach 1:
The patent applies segmentation by dividing the field generating coil into multiple discrete elongated portions (first elongated portion and second elongated portion) that are separately positioned and dimensioned. This segmented configuration allows independent optimization of each portion's dimensions and positioning to maximize signal strength and resolution while maintaining manufacturability through standard PCB fabrication processes.
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 measurement accuracy and robustness by reducing end effects and misalignment sensitivity, allowing for a more compact and cost-effective design with improved signal strength and resolution.
Implementation Method 1
a first-track field generating coil portion configured to nominally surround a first-track generated field area aligned with the first pattern track and generate a first-track changing magnetic flux in the first-track generated field area in response to the coil drive signal
Implementation Method 2
a conductive shield region to mitigate periodic errors and misalignment sensitivity
Data Source
AI summary
An electronic position encoder includes a scale and detector. The detector includes a field generating coil (FGC) having elongated portion configurations (EPCs) bounding a generated field area (GFA) aligned with sensing elements in a sensing area, to provide position signals responsive to the scale interacting with the generated field. Sensing elements and EPCs are fabricated in “front” layers of the detector portion. The EPCs include end gradient arrangements (EGAs) configured to reduce field strength in the generated field area as a function of position along the x-axis direction for positions approaching the end of the GFA. A shielded transverse conductor portion (TCP) fabricated in a “rear” layer connects the EPCs and/or EGAs of the FGC via feedthroughs. A conductive shield region (CSR) configuration in a CSR layer between the front and rear layers intercepts at least a majority of a projection of the TCP toward the front layers.