Position Detection Device Edge Validity Filtering
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Solution Overview
Problem
Existing position detection systems, such as optical encoders, are susceptible to errors caused by foreign matter and noise, leading to inaccurate position detection.
Innovation Solution
A position detection device that includes an edge detection unit for binarizing image signals, an edge evaluation unit for determining edge validity, a code string generation unit for generating code strings, a coarse position calculation unit for calculating positions in bit period units, a phase calculation unit for determining relative deviations, and an absolute position calculation unit for combining coarse and phase data to achieve robust and accurate position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If edge detection is performed by binarizing image signals, then position detection resolution is improved, but susceptibility to foreign matter and noise increases
Solution Approach 1:
The patent segments the edge detection process into multiple independent evaluation criteria (bit period comparison, histogram analysis, adjacency verification). Each criterion independently evaluates edge validity, and the results are combined to determine final edge acceptance. This segmentation allows the system to maintain high resolution while cross-validating edges against multiple standards, thereby reducing susceptibility to noise and foreign matter.
Solution Approach 2:
The patent implements feedback mechanisms where edge detection results are continuously evaluated and refined. The edge evaluation unit uses feedback from multiple evaluation criteria (bit period comparisons, histogram distributions, adjacency checks) to adjust and verify edge determinations. This feedback loop ensures that only reliable edges are accepted, maintaining both high resolution and robustness against disturbances.
2Measurement precision
If correlation calculation is performed between code string and code pattern, then position detection accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent performs preliminary actions by pre-processing the code pattern and image signal before the main correlation calculation. The code string is generated from detected edges using established rules, and the image signal is binarized in advance. This preliminary preparation simplifies the subsequent correlation calculation between the code string and code pattern, reducing computational complexity while maintaining high accuracy.
Solution Approach 2:
The patent extracts only the essential information needed for position detection from the complex image signal. By binarizing the image and generating a condensed code string from detected edges, the system extracts the critical positional data while discarding unnecessary information. This extraction reduces the computational burden of the correlation calculation while preserving position detection accuracy.
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
The device effectively suppresses error detection of edges, enabling highly accurate and robust position detection by removing invalid edges affected by foreign matter and noise.
Implementation Method 1
a light-receiving element for receiving light irradiated from a light source toward a scale having a code pattern
Data Source
AI summary
To obtain a position detection device capable of detecting highly accurate and robust position by suppressing affect of error detection of an edge, provided is a configuration for performing a validity determination of edges detected by binarizing an image signal (21) converted by a light-receiving element (3) for receiving light irradiated from a light source (1) toward a scale (2) having a code pattern, and performing position detection after removing the edges determined to be invalid as edges that have been affected by foreign matter and the like among the edges on which the validity determination has been performed.