Slit Position Calibration for Absolute-Angle Errors
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Solution Overview
Problem
Existing position detection apparatuses face errors in slit number determination due to large absolute angle errors, leading to incorrect interpolation angles and potential wrong difference values in correction tables, which can result in inaccurate position calculations.
Innovation Solution
A calibration apparatus and method that acquires detection positions, calculates errors between actual and ideal slit positions, determines overlapping slit numbers, and generates correction values to unify errors, using Fourier series expansion for precise correction functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the slit number is determined based on the absolute angle without error correction, then the position detection process is simple, but the slit number may be wrong when the absolute angle error is large, leading to incorrect correction values being read from the correction table
Solution Approach 1:
The patent performs preliminary calibration to generate correction values before actual position detection. The calibration process pre-calculates correction values for various absolute angle errors and stores them in a correction table. During operation, the system simply retrieves the appropriate correction value based on the detected absolute angle error, avoiding complex real-time calculations while ensuring accurate slit number determination.
Solution Approach 2:
The patent introduces a correction table as an intermediary between the absolute angle measurement and the slit number determination. The correction table stores pre-calculated correction values that mediate the relationship between the measured absolute angle (which may contain errors) and the correct slit number. This intermediary structure allows the system to handle measurement errors without requiring complex real-time error analysis.
2Measurement precision
If correction values are generated for each detection position, then the position detection accuracy is improved, but the data processing and correction value generation complexity increases
Solution Approach 1:
The patent segments the position detection range into multiple detection positions and generates correction values for each segment. By dividing the overall detection range into smaller segments, the system can manage the complexity of correction value generation more effectively. Each segment's correction values are generated independently, allowing for more precise local corrections without overwhelming the processing system.
Solution Approach 2:
The patent changes the parameter of detection position into discrete segments rather than treating it as a continuous variable. This parameter change allows the system to generate correction values for specific discrete positions, making the correction process more manageable. The Fourier series expansion is then used to interpolate between these discrete points, achieving high precision without requiring correction values for every possible position.
3Measurement precision
If the Fourier series expansion is used to calculate correction function parameters, then the correction precision is improved, but the calculation time and processing complexity increase
Solution Approach 1:
The patent performs the computationally intensive Fourier series expansion calculations during the calibration phase, before actual position detection begins. The correction function parameters are pre-calculated and stored. During operational use, the system only needs to evaluate the already-established correction function, which is much faster than performing full Fourier series expansion in real-time. This separates the heavy computational workload from the time-critical detection operations.
Data Source
AI summary
Provided is a calibration apparatus including: an acquisition unit for acquiring a detection position of a mobile body for each actual position of the mobile body; a calculation unit for calculating, for a detection position of each actual position of the mobile body, an error between a slit position signal for detecting a slit position and an ideal slit number corresponding to the actual position; a determination unit for determining whether two or more actual positions having at least partially different slit numbers in units of first slits of a predefined number correspond to a same detection position; and a generation unit for generating, in response to the two or more actual positions corresponding to a same detection position, a correction value for correcting an error by a magnitude between errors at the two or more actual positions with respect to the slit position signal at the detection position.