Position Measuring Device Grid Scale Absolute Encoding
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Solution Overview
Problem
Existing position measuring devices face challenges with low tolerance for relative displacements and rotations, complex image processing, and susceptibility to contamination, particularly in single-track systems with limited resolution and compact designs.
Innovation Solution
A position measuring device with a single track scale featuring a grid of strip elements with periodic structures for absolute position coding, utilizing a two-dimensional detector arrangement to generate phase-shifted incremental signals and absolute position signals, ensuring high-resolution measurements and robustness against contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-track system with a compact design is used, then the device complexity is reduced and mounting tolerances are improved, but the measurement precision and resolution are worsened
Solution Approach 1:
The patent transitions from one-dimensional incremental encoding to two-dimensional absolute position encoding by arranging structural elements in a grid pattern with rows and columns. The row index provides coarse absolute position information while the column index provides fine resolution, achieving high-resolution absolute measurement within a compact single-track design.
Solution Approach 2:
The measurement track is segmented into multiple independent reading fields arranged in a grid pattern. Each reading field contains structural elements that can be independently detected, allowing the system to determine absolute position through combinatorial encoding of row and column indices while maintaining a compact single-track structure.
2Measurement precision
If a multi-track system with separate absolute and incremental tracks is used, then the measurement precision is improved, but the device complexity and mounting tolerance requirements are worsened
Solution Approach 1:
The patent merges absolute position encoding and incremental measurement functions into a single integrated track. The grid-patterned structural elements simultaneously provide absolute position information through their two-dimensional arrangement and incremental position information through their periodic variation along the measurement direction, eliminating the need for separate multi-track structures.
Solution Approach 2:
The single track with grid-patterned structural elements serves multiple functions: it provides absolute position encoding through the two-dimensional grid arrangement, incremental position measurement through periodic variations, and serves as both the scale and the reference structure, replacing the need for separate absolute and incremental tracks.
3Device complexity
If a single-track system with a very small scanning field is used, then the device complexity is reduced, but the susceptibility to contamination is worsened
Solution Approach 1:
The patent expands the scanning field by utilizing two-dimensional grid-patterned structural elements instead of one-dimensional patterns. This allows the scanning unit to read multiple reading fields simultaneously or sequentially across a larger area, reducing susceptibility to contamination while maintaining the simplicity of a single-track design.
4Ease of operation
If conventional single-track systems are used, then the mounting tolerances are improved, but the signal generation is susceptible to interference and contamination
Solution Approach 1:
The track is segmented into multiple reading fields arranged in a grid pattern, with each field containing multiple structural elements. This segmentation allows the system to generate multiple independent signals that can be combined to produce interference-free absolute position information, improving signal robustness while maintaining easy mounting tolerances.
Solution Approach 2:
The patent uses multiple copies of structural elements within each reading field and across the grid pattern. These redundant copies provide multiple signal sources that can be processed to eliminate interference and contamination effects, ensuring reliable signal generation while maintaining the simplicity of a single-track design with generous mounting tolerances.
Data Source
Figure 1~2
Figure 3a
Figure 3b
AI summary
The present invention relates to a position measuring device for absolute position determination, comprising a scale and a scanning unit movably arranged relative to the scale along at least one measuring direction. The scale has a measuring division to generate a scannable signal pattern, which, along the measuring direction, comprises a grid of strip elements arranged with a scale longitudinal period. For absolute position encoding along a transverse direction oriented perpendicular to the measuring direction, the strip elements have a periodic structure with a scale transverse period. For scanning the signal pattern, the scanning unit comprises a two-dimensional detector arrangement with a plurality of detector elements, consisting of several detector slits, each containing several detector elements.Here, the detector slits are arranged periodically along the measuring direction and the detector elements along the transverse direction, so that at least three periodic partial-incremental signals with respect to relative movements along the measuring direction and at least one absolute position signal per detector slit can be generated from the sampling of the signal pattern (Fig. 2).