Position Measuring Scale With Offset Graduation Tracks
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Solution Overview
Problem
Position-measuring devices face inaccuracies due to non-optimal adjustments, particularly when '1 out of 8 gaps' in incremental tracks cause phase shifts and measurement errors, especially in optical scanning systems where illumination and detector alignment are not perfectly parallel.
Innovation Solution
A scale with two P-periodic graduation tracks offset transversely to the measuring direction, each with integrated reference markings offset relative to one another, and a structured detector with sensors arranged to omit certain sensors at varying distances to cancel out measurement errors when linked suitably.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference markings are integrated at regular intervals in the incremental track, then absolute position determination is improved, but measurement precision deteriorates due to phase shifts from non-optimal adjustments
Solution Approach 1:
The incremental track is divided into multiple segments (first and second incremental tracks) with different periods. Each segment handles a specific measurement range, allowing the system to maintain high precision across the entire measurement range while reducing the impact of phase shifts from non-optimal adjustments.
Solution Approach 2:
The patent introduces a third dimension by adding a second incremental track with a different period (1.25x the first track's period). This dimensional expansion allows the system to compensate for phase shift errors through multi-track evaluation, improving measurement reliability under non-optimal adjustment conditions.
2Device complexity
If a single incremental track with reference markings is used, then device complexity is reduced, but measurement precision deteriorates due to uncompensated phase shifts
Solution Approach 1:
The scale is segmented into multiple incremental tracks with different periods rather than using a single complex track. This segmentation allows each track to be simpler in design while collectively providing high measurement precision through their combined evaluation.
Solution Approach 2:
The patent uses a composite approach by combining multiple incremental tracks with different periods (1:1.25 ratio) to create a multi-track evaluation system. This composite structure achieves high measurement precision that would be difficult to obtain with a single track design.
3Adaptability or versatility
If the measurement range is extended using multiple tracks, then adaptability is improved, but device complexity increases due to multiple detector tracks and sensors
Solution Approach 1:
The detector is designed with multi-functionality by using the same detector track structure for both the first and second incremental tracks. The detector can evaluate both tracks simultaneously, reducing the need for separate detector structures and thereby reducing overall device complexity despite the extended measurement range.
Solution Approach 2:
The patent maintains homogeneity in the detector design by using identical detector track structures for both incremental tracks. This homogeneous approach simplifies the overall detector design and reduces complexity compared to using different detector structures for different measurement ranges.
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 significantly reduces measurement errors by ensuring that phase shifts from non-optimal adjustments are compensated, resulting in more accurate position values even when the device is not optimally adjusted.
Implementation Method 1
a structured photodetector with numerous sensor fields, which records many periods of the scale simultaneously
Data Source
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AI summary
The basic principle of a scale (M) or a position measuring device according to the invention is the displacement of reference markings (R) in graduation tracks (TS1, TS2) offset transversely to the measuring direction (X) by fractions of the distance (A) between the reference markings (R) within a graduation track (TS1, TS2). This provides a way to eliminate or at least significantly reduce the negative effects of the disturbance of the periodicity (P) of a graduation track (TS1, TS2) caused by the reference markings R.