Electromagnetic Induction Encoder Parallel Coil Design
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Solution Overview
Problem
Conventional electromagnetic induction type encoders face challenges in obtaining strong signal detection due to signal attenuation caused by impedance in scale coils, making it difficult to achieve high precision and reduce encoder size.
Innovation Solution
The configuration includes adding coil lines to both sides of scale coils with different or equal areas and thicknesses, allowing for increased induced current and improved signal intensity without altering the magnetic field distribution, enabling more precise measurements and downsizing the encoder.
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 of scale coils becomes long causing signal attenuation
Solution Approach 1:
The patent combines multiple scale coil rows by electrically connecting them in parallel through conductor lines. This merging approach maintains the offset cancellation capability of multiple rows while reducing the effective impedance, thereby preventing signal attenuation and maintaining strong induced currents in the receiver coils.
Solution Approach 2:
The scale coils are designed to serve multiple functions simultaneously: they generate magnetic fields for position detection, cancel offset through symmetric arrangement, and maintain low impedance through parallel connection. This multi-functionality allows the system to achieve both offset reduction and signal strength without compromise.
2Volume of moving object
If scale width is reduced to downsize encoder, then encoder width is reduced, but signal intensity decreases
Solution Approach 1:
By connecting multiple scale coil rows in parallel, the patent effectively reduces the impedance of each coil. This allows the use of shorter scale coils within a reduced encoder width while maintaining sufficient signal intensity, as the parallel connection compensates for the reduced individual coil length.
Solution Approach 2:
The patent changes the electrical parameters of the scale coil system by connecting multiple coils in parallel, which reduces the overall impedance. This parameter change allows the system to maintain strong induced currents even with shorter scale coils in a compact encoder design.
3Measurement precision
If multiple tracks with different scale pitches are used to measure absolute position, then absolute position measurement is enabled, but the scale coil line becomes longer causing signal attenuation
Solution Approach 1:
The patent applies parallel connection of scale coils across multiple tracks with different scale pitches. This merging of electrical paths reduces the effective impedance for each track, enabling absolute position measurement across multiple scales while preventing signal attenuation that would otherwise result from the extended coil lines.
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 signal intensity, improves measurement accuracy by increasing the S/N ratio, and reduces encoder width, allowing for more precise and compact designs.
Implementation Method 1
the encoder detects a relative displacement between the scale 10 and the grid 12 on the basis of a flux change detected at the receiver coil via the scale coil when the transmitter coil is excited
Implementation Method 2
a flux change detected at the receiver coil via the scale coil when the transmitter coil is excited
Data Source
AI summary
In an electromagnetic induction type absolute position measuring encoder having two or more tracks which includes: two or more rows of scale coils, each row including scale coils numerously arranged on a scale along a measuring direction so as to have a scale pitch different from that of another row; and transmitter coils and receiver coils provided on a movable grid relative to the scale in the measuring direction so as to face the scale coils, and which can measure an absolute position of the grid with respect to the scale on the basis of a flux change detected at the receiver coil via the scale coil when the transmitter coil is excited, coil lines are added to at least one side of the scale coils in the measuring direction at least in one of the tracks.