Displacement Detecting Device Self-Calibration Curve
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Solution Overview
Problem
Existing displacement measuring devices, such as encoders, face measurement errors due to scale distortion during installation, which are difficult to correct without expensive and labor-intensive setup of highly accurate displacement sensors, and self-calibration methods are limited by sensor spacing and cost.
Innovation Solution
A displacement detecting device with a movable detecting unit having multiple detection portions and a calculating portion that generates a self-calibration curve by varying the distances between detection points, allowing for accurate measurement error correction without a laser interferometer or reference scale, enabling finer graduations and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors are arranged at predetermined intervals for self-calibration, then measurement error can be calibrated without highly accurate displacement sensors, but the sampling interval becomes equal to the arrangement pitch, limiting the frequency of measurement error that can be calibrated
Solution Approach 1:
The detecting unit is divided into multiple detection portions (at least three) arranged along the scanning direction with different spacing. This segmentation allows the system to obtain measurement data at multiple positions simultaneously, effectively reducing the sampling interval below the physical spacing between detection portions through computational processing.
Solution Approach 2:
The patent transitions from a single-line sensor arrangement to a multi-dimensional detection configuration where detection portions are distributed across different positions. By combining data from these multiple spatial positions and applying signal processing techniques, the system achieves effective sampling at intervals finer than the physical sensor spacing.
2Manufacturing precision
If the pitch of arrangement of sensors is narrowed to increase sampling frequency, then higher frequency measurement error can be calibrated, but the minimum physical distance required to avoid interference limits how narrow the pitch can be
Solution Approach 1:
The patent introduces computational processing as an intermediary between the physical sensor arrangement and the measurement output. By using calculation portions to process signals from multiple detection portions with different spacing, the system achieves fine sampling resolution without requiring physically close sensor placement, thus avoiding sensor interference.
Solution Approach 2:
The patent replaces the mechanical constraint of sensor spacing with a computational solution. Instead of relying on physical proximity to achieve fine sampling intervals, the system uses mathematical processing of signals from spatially distributed detection portions to achieve equivalent or superior sampling resolution.
3Measurement precision
If a highly accurate displacement sensor such as a laser interferometer is used for error evaluation, then accurate measurement error data can be obtained, but the cost and labor for setting up and maintaining such sensors becomes excessive
Solution Approach 1:
The patent implements self-service calibration where the encoder system uses its own detection portions to generate calibration data. The detecting unit with multiple detection portions performs self-measurement, and the calculation portion processes this data to create correction information, eliminating the need for external highly accurate displacement sensors and their associated setup and maintenance requirements.
Solution Approach 2:
The patent creates a simplified copy of the measurement function using the encoder's own detection portions rather than requiring a full-scale laser interferometer system. By using multiple detection portions with different spacing to simulate the measurement process, the system achieves calibration capability without replicating the complex infrastructure of professional measurement equipment.
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 allows for accurate calibration of measurement errors at a lower cost by setting a sampling interval shorter than the detection portion spacing, improving encoder accuracy without the need for expensive sensors.
Implementation Method 1
a scale which has an optical lattice; a detecting unit which is disposed so as to be movable in a scanning direction relative to the scale and which has n (n is an integer not smaller than 3) detection portions... arranged in the scanning direction for detecting position information from the optical lattice
Data Source
AI summary
A displacement detecting device includes: a scale which has an optical lattice; a detecting unit which is disposed so as to be movable in a scanning direction relative to the scale, inclusive of at least a first detection portion, a second detection portion and a third detection portion, arranged in the scanning direction for detecting position information from the optical lattice; and a calculating portion configured to obtain a self-calibration curve on graduations of the scale by specifying positions of the detection portions and calculating measurement error based on the position information detected by the detecting unit, wherein: the detecting unit is provided so that a distance between the first detection portion and the second detection portion and a distance between the second detection portion and the third detection portion are different from each other and do not form an integral multiple.