Vernier Encoder Scale Track Boundary Pattern Arrangement
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Solution Overview
Problem
Vernier encoders with multiple track scales face position detection errors due to mechanical backlash, causing cross-talk and accuracy issues when the sensor and scale are relatively shifted in the scale width direction, which existing solutions attempt to mitigate by increasing sensor size or using complex signal processing.
Innovation Solution
A vernier encoder scale design that allows increased relative movement between the sensor and multiple track scale in the scale width direction without enlarging the sensor or encoder, by strategically arranging periodic patterns with different periods and optimizing their positions relative to the track boundary to minimize cross-talk and maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor size is increased to reduce cross-talk caused by mechanical backlash, then position detection accuracy is improved, but the encoder size increases
Solution Approach 1:
The scale is divided into multiple scale tracks (first scale track, second scale track, etc.) arranged in the scale width direction. Each scale track contains periodic patterns that are read by corresponding light receivers in the sensor. This segmentation allows the sensor to read multiple tracks simultaneously, and through signal processing (adding or subtracting sensor output signals from different tracks), cross-talk caused by mechanical backlash is suppressed while maintaining high position detection accuracy without increasing sensor size.
2Measurement precision
If the distance between light emitter and light receiver is increased to suppress cross-talk, then position detection accuracy is improved, but the encoder size increases
Solution Approach 1:
Instead of increasing the distance in the optical path direction (Z direction) between the light emitter and light receiver, the solution arranges multiple scale tracks in the scale width direction (Y direction), which is orthogonal to the position detection direction. This dimensional change allows cross-talk suppression through track separation rather than through increased optical path distance, thereby avoiding an increase in encoder size while maintaining high position detection accuracy.
3Measurement precision
If multiple scale tracks are used to suppress cross-talk, then position detection accuracy is improved, but device complexity increases
Solution Approach 1:
Multiple scale tracks are arranged adjacently in the scale width direction, and multiple light receivers are arranged to face corresponding periodic patterns in different scale tracks. The sensor unit integrates these light receivers and reads periodic patterns from multiple scale tracks simultaneously. Through signal processing (combining sensor output signals from different tracks), cross-talk is suppressed and high position detection accuracy is achieved. This merging approach distributes the complexity across multiple simple tracks rather than requiring a single complex track.
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 design enhances synchronization and position detection accuracy by suppressing the influence of relative positional shifts, allowing for high-accuracy position detection without increasing the encoder's size, even with significant backlash, and improves the robustness of position detection across varying shifts.
Implementation Method 1
the sensor optically or magnetically reads the periodic pattern in the scale to produce an electric signal (sensor output signal) corresponding to the periodic pattern
Implementation Method 2
The scale is provided with a periodic pattern periodically transmitting or reflecting light
Implementation Method 3
The scale is provided with a periodic pattern periodically transmitting or reflecting light or periodically changing intensity of magnetic field
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
The scale (2) for a vernier encoder including a sensor (7) relatively movable with the scale in a first direction and configured to read periodic patterns provided in the scale. The scale includes first and second scale tracks (8, 11) each including multiple periodic patterns (111, 112, 211, 212) having mutually different periods in the first direction and being arranged parallel in a second direction. The multiple periodic patterns form, between the first and second scale tracks, multiple pairs of periodic patterns to be used for producing multiple periodic signals, each periodic signal being produced by vernier operation. In at least one of the first and second scale tracks, a first periodic pattern (111, 211), which is used for producing a shortest period periodic signal among the multiple periodic signals, is provided closest to a boundary (31) between the first and second scale tracks among the multiple periodic patterns.