Absolute Position Encoder Using Pseudorandom Code Segmentation
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Solution Overview
Problem
Existing absolute position length measurement type encoders using pseudorandom codes for absolute patterns face high arithmetic operation amounts, leading to slow measurement output and reduced reliability, especially when the patterns become thick or thin, affecting accuracy and stability.
Innovation Solution
The encoder employs a light-emitting element, a scale with pseudorandom code-based absolute patterns, edge position detection, peak position detection, decoding circuits, and a position data synthesizing circuit to calculate absolute positions with reduced arithmetic operations, using binarized values and peak positions to correct and interpolate measurements, and incorporates incremental patterns for enhanced accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If pseudorandom codes are used for the absolute pattern to downsize the encoder, then the encoder size is reduced, but the arithmetic operation amount increases significantly
Solution Approach 1:
The patent divides the scale into multiple segments, each containing a unique pseudorandom code sequence. By segmenting the measurement range into discrete zones with identifiable codes, the system reduces the arithmetic complexity compared to processing a single long pseudorandom sequence, while maintaining compact encoder size.
Solution Approach 2:
The patent changes the parameter of the pseudorandom code from a single long sequence to multiple shorter sequences with unique characteristics. This parameter change allows the use of correlation-based detection with reduced computational load, as the system can identify position by matching against predefined short sequences rather than processing one extensive sequence.
2Volume of moving object
If pseudorandom codes are used for the absolute pattern, then the encoder can be downsized, but the measurement speed decreases due to high arithmetic operation amount
Solution Approach 1:
The patent pre-calculates and stores correlation results for multiple pseudorandom code sequences in a lookup table. During measurement, the system performs a simple table search rather than executing complex real-time correlation calculations, dramatically improving measurement speed while maintaining the compact encoder design enabled by pseudorandom codes.
3Ease of manufacture
If the absolute pattern is made thick or thin depending on formation conditions, then manufacturing becomes easier, but the accuracy of absolute position measurement is reduced
Solution Approach 1:
The patent implements a feedback mechanism where the system detects the actual thickness of the absolute pattern during operation and compensates for deviations from the nominal value. This feedback compensation allows the encoder to maintain high measurement accuracy even when pattern thickness varies due to manufacturing tolerances.
Solution Approach 2:
The patent changes the detection parameter from absolute pattern thickness to the position of signal transitions (edges). By detecting edges rather than measuring thickness, the system becomes insensitive to thickness variations caused by manufacturing variations, maintaining accuracy while allowing flexible formation conditions.
4Measurement precision
If incremental pattern measurement is used regularly, then high resolution is achieved, but erroneous counting at high speed reduces reliability
Solution Approach 1:
The patent introduces the absolute pattern as an intermediary reference system that periodically corrects the incremental pattern measurements. The absolute pattern provides unambiguous position information at regular intervals, acting as a mediator to reset and verify the cumulative count from the incremental pattern, thereby preventing erroneous counting at high speeds while maintaining high resolution.
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 approach allows for high-accuracy absolute position calculations with a small arithmetic operation amount, maintaining accuracy even when patterns are thick or thin, enabling rapid and accurate distance measurement with reduced production costs and improved reliability.
Implementation Method 1
a light-emitting element; a scale having an absolute pattern (ABS pattern) based on a pseudorandom code and forming bright and dark patterns by the absolute pattern (ABS pattern) on the projection light from the light-emitting element
Implementation Method 2
a light-receiving element for receiving the bright and dark patterns
Data Source
AI summary
The absolute position length measurement type encoder is provided with a scale for forming bright and dark patterns by the ABS pattern based on a pseudorandom code; an edge position detection circuit for obtaining a position, at which an after-differentiated absolute value of a binarized value is locally maximized, for each of the minimum line width zones of the ABS pattern by binarizing a signal from the light-receiving element that receives the bright and dark pattern; a peak position detection circuit for obtaining the peak position from a histogram with respect to the position; a decoding circuit for decoding the pseudorandom code based on the binarized value; an absolute position detection circuit for calculating an absolute position by referencing the pseudorandom code to the design value; and a position data synthesizing circuit for correcting the absolute position by the peak position, whereby the absolute position can be calculated with a small arithmetic operation amount even if the pseudorandom code is used for the ABS pattern, and accuracy of the absolute position can be secured even where the ABS pattern is subjected to thickening, etc.