Inductive Position Sensor Winding Cancellation
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Solution Overview
Problem
Inductive position sensors face issues with measuring distortions due to uneven direct coupling between windings, which worsen as the gap between the scale and reading head increases, leading to reduced coupling and accuracy.
Innovation Solution
The windings are divided into pairs of identical elements with specific relative locations and polarities, ensuring opposite polarity couplings between drive and sense windings within each pair, which cancel out direct couplings and maintain consistent signal variations, allowing for a larger gap and reduced distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gap between scale and reading head increases, then mechanical tolerance and smoothing of distortions improve, but coupling strength decreases leading to reduced measurement accuracy
Solution Approach 1:
The windings are divided into multiple identical winding elements arranged in distinct patterns. Each pattern produces a coupling signal, and by combining signals from multiple patterns, the overall coupling strength is enhanced while maintaining the ability to operate at larger gaps where mechanical tolerance is improved.
Solution Approach 2:
Signals from multiple winding element patterns are combined through additive superposition. This merging of signals reinforces the useful coupling signal while the opposing polarity configuration cancels harmful direct couplings, effectively increasing the signal-to-noise ratio and maintaining measurement accuracy at larger gaps.
2Object-affected harmful factors
If direct coupling between windings is reduced by increasing gap, then harmful direct coupling effects decrease, but useful coupling via scale also decreases
Solution Approach 1:
The invention uses the harmful direct coupling effect beneficially by arranging winding elements with opposite polarities. The direct coupling signals from these oppositely polarized elements cancel each other out, converting the harmful direct coupling into a beneficial cancellation mechanism that eliminates distortion while preserving useful scale-mediated coupling.
Solution Approach 2:
The winding elements are arranged in asymmetric polarity configurations where adjacent elements have opposite polarities. This asymmetric arrangement ensures that direct coupling paths between oppositely polarized elements produce canceling effects, while the scale-mediated coupling paths maintain their useful signal transmission.
3Measurement precision
If winding elements are arranged to cancel direct coupling, then measurement distortion decreases, but device complexity increases
Solution Approach 1:
Each local winding element is designed with a specific polarity and position to achieve the cancellation effect locally. By assigning different polarities to different local elements, the system achieves uniform signal output across the entire reading head while maintaining a relatively simple overall structure that can be implemented using standard printed circuit board techniques.
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 accuracy by eliminating direct coupling effects, allowing for a larger gap between the scale and reading head, smoothing out distortions, and maintaining uniform signal variations, suitable for precise applications like digital indicators and calipers.
Implementation Method 1
the signal coupled from one winding to another via the scale's spatially periodic features varies sinusoidally with the reading head's position along the scale
Implementation Method 2
All windings, whether inducing (drive windings) or induced (sense windings), are interlaced in the same area facing the scale's full width
Data Source
AI summary
An inductive position sensor has a spatially periodic scale with a series of conducting or permeable features of pitch T and a reading head with drive windings and sense windings, facing the scale with a spatial period 2T along the scale. The windings are each divided in two identical winding elements,having the same relative location within two identical winding element patterns having a center-to-center distance along the scale of NT+T/2, N being an integer, and connected so that the winding element polarities in each winding are either opposed for drive windings and the same for sense windings or the same for drive windings and opposed for sense windings. Thereby, direct couplings in both patterns cancel each other, while the spatially periodic signals coupled via the scale reinforce each other.