Electromagnetic Inductive Encoder Single-Track Absolute Positioning
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Solution Overview
Problem
Existing electromagnetic inductive encoders require multiple tracks to calculate the absolute position of a read head relative to a scale, leading to increased size and cost, as forming absolute patterns randomly on the scale is difficult, necessitating the combination of incremental signals for position calculation.
Innovation Solution
An electromagnetic inductive encoder with a scale pattern that includes first and second patterns, allowing the reception coil to receive positive and negative currents respectively, enabling the generation of a pseudo-random code signal from a single track for absolute position calculation, reducing the number of tracks needed and allowing flexibility in scale design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple tracks are used to calculate absolute position by combining incremental signals, then the absolute position calculation capability is improved, but the scale size increases
Solution Approach 1:
The patent merges the functions of multiple tracks into a single track by using multiple reception coils arranged in the measurement direction. Each reception coil detects signals from scale patterns at different positions, and the computation unit combines these signals to calculate absolute position, thereby achieving the functionality of multiple tracks while using only one physical track
Solution Approach 2:
The patent transitions from using multiple tracks in the orthogonal direction to using multiple reception coils in the measurement direction. This dimensional shift allows the system to maintain absolute position calculation capability while reducing the scale's width in the orthogonal direction, thus solving the contradiction between measurement capability and scale size
2Measurement precision
If multiple tracks are used to calculate absolute position, then the absolute position calculation capability is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple track functions into a single track by implementing multiple reception coils along the measurement direction. This reduces the number of physical tracks from multiple to one, thereby simplifying the device structure while maintaining the capability to calculate absolute position through signal combination in the computation unit
3Measurement precision
If multiple tracks are used to calculate absolute position, then the absolute position calculation capability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent merges multiple track functionalities into a single track with multiple reception coils, reducing the total amount of wiring patterns and scale structure that need to be manufactured. This simplification directly reduces manufacturing complexity and cost while preserving the absolute position calculation capability through computational signal processing
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 enables the calculation of absolute position from a single track, reducing the size and cost of the scale while maintaining flexibility in design, and improving signal efficiency by alternately juxtaposing transmission and reception coils.
Implementation Method 1
a transmission coil that transmits a magnetic flux to the scale pattern to cause the scale pattern to produce electromotive current
Implementation Method 2
a reception coil that receives, in a form of current, a change in the magnetic flux created by the electromotive current and sent from the scale pattern
Data Source
AI summary
There is provided an electromagnetic inductive encoder that allows reduction in the number of tracks on a scale for reduction in the size of the scale. The electromagnetic inductive encoder includes a scale having a scale pattern, a head, and computation unit. The head includes transmission unit, which includes transmission coils, and reception unit, which includes reception coils. The scale pattern has a first pattern, which causes the reception coils to receive positive current, and a second pattern, which causes the reception coils to receive negative current. The computation unit includes a determination unit, which, when the positive current is detected, determines that the current is associated with the first pattern, and, when the negative current is detected, determines that the current is associated with the second pattern, a signal generation unit, which generates a signal formed of “1” representing the first pattern and “0” representing the second pattern based on the result of the determination, and a position calculation unit, which calculates the position of the head based on the signal generated by the signal generation unit.