Electromagnetic Encoder Scale Coil Segmentation for Signal Crosstalk
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Solution Overview
Problem
Conventional electromagnetic induction type encoders face challenges in achieving strong signal detection due to signal attenuation and crosstalk, which affects measurement accuracy and precision, especially when trying to reduce encoder width and scale width.
Innovation Solution
The implementation of an electromagnetic induction type absolute position measuring encoder with two or more tracks of scale coils having different pitches, where at least one loop-shaped additional scale coil is added between the original scale coils, and the receiver coil covers both original and additional scale coils, enhancing signal strength and reducing crosstalk effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If three rows of scale coils are arranged to reduce offset, then offset is reduced, but the line length of scale coils becomes long causing signal attenuation
Solution Approach 1:
The invention divides the scale coil structure into multiple independent rows (first row with first scale coils, second row with second scale coils) having different line lengths. This segmentation allows each row to serve a specific function: the first row with longer line length reduces offset, while the second row with shorter line length maintains strong signal generation, thereby resolving the contradiction between offset reduction and signal strength.
2Length of stationary object
If scale width is reduced to downsize encoder, then encoder width is reduced, but signal attenuation increases due to longer scale coil line length
Solution Approach 1:
The invention segments the scale coil system into multiple rows with different characteristics. The second row of scale coils is specifically designed with shorter line length to compensate for signal attenuation that would otherwise occur when reducing encoder width. This allows the encoder to be downsized while maintaining adequate signal strength through the optimized second row.
Solution Approach 2:
The invention creates a composite scale coil system combining two types of scale coils with different line lengths and positions. This composite structure leverages the advantages of both configurations: the first row provides offset reduction capability while the second row ensures sufficient signal generation, enabling encoder downsizing without sacrificing signal strength.
3Measurement precision
If multiple tracks with different scale pitches are added to improve measurement precision, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The invention implements multi-functionality by having two rows of scale coils serve different purposes within the same encoder system. The first row primarily reduces offset, while the second row primarily generates strong signals. Both rows work together to achieve high measurement precision, thereby obtaining multiple benefits (offset reduction + strong signal) without proportionally increasing device complexity.
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 increases signal detection strength, improves measurement precision by enhancing the signal-to-noise ratio, allows for downsizing the encoder, and enhances wide-range accuracy by minimizing crosstalk-induced current effects.
Implementation Method 1
The electromagnetic induction type encoder detects an amount of relative movement between the scale 10 and the grid 12 from a flux change detected at the receiver coil via the scale coil when the transmitter coil is excited.
Implementation Method 2
The electromagnetic induction type encoder detects an amount of relative movement between the scale 10 and the grid 12 from a flux change detected at the receiver coil via the scale coil when the transmitter coil is excited.
Data Source
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AI summary
An electromagnetic induction type absolute position measuring encoder having two or more tracks, includes: two or more rows of scale coils (14-1), each of the rows including a large number of scale coils (14-1) arranged on a scale along a measuring direction so as to have a scale pitch (λ1; λ2) different from that of another row; a transmitter coil (24-1) and a receiver coil (20-1) arranged on a grid movable relative to the scale in the measuring direction so as to face the scale coils (14-1); and the track constituted by the scale coils (14-1), the transmitter coil (24-1) and the receiver coil (20-1), the encoder being capable of measuring an absolute position of the grid with respect to the scale from a flux change detected at the receiver coil (20-1) via the scale coils (14-1) when the transmitter coil (24-1) is excited, in which at least one loop-shaped additional scale coil (14-1b) is added between the scale coils (14-1) in at least one of the tracks. Accordingly, an induced current at the scale coil (14-1) when the transmitter coil (24-1) is excited is increased, thereby improving a detection signal strength at the receiver coil (20-1), and an induced current due to a crosstalk magnetic field is reduced. As a result, a measuring accuracy is improved.