Absolute Position Code Using Coprime Sequence Segments
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Solution Overview
Problem
Existing absolute position measuring devices face challenges in achieving high resolution within a measuring range due to the complexity of decoding multiple code words, which requires large decoding tables and leads to long calculation times.
Innovation Solution
The use of multiple code sequences of different lengths, arranged in a common track with segments of at least three code elements, where the lengths of the code sequences are coprime, allowing for unique absolute encoding and decoding using shorter tables, combined with an incremental track for further resolution through interpolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple code sequences of different lengths are used to achieve high resolution absolute position encoding, then measurement precision is improved, but device complexity increases due to the need for multiple decoding tables and longer calculation times
Solution Approach 1:
The code track is divided into multiple code sequences of different lengths (e.g., 3, 5, 7 code elements) that are arranged in a predetermined sequence. Each code sequence can be decoded independently using separate decoding tables, segmenting the complex decoding task into smaller, manageable parts that can be processed in parallel or sequentially with reduced computational burden.
Solution Approach 2:
The patent transitions from a single-dimensional code word approach to a multi-dimensional approach by using multiple code sequences of different lengths arranged in a predetermined sequence. This dimensional expansion allows the system to encode more position information while enabling modular decoding through multiple smaller tables rather than one large table.
2Measurement precision
If a large decoding table is used to store all possible code words for high resolution, then measurement precision is improved, but loss of time increases due to longer calculation times for decoding
Solution Approach 1:
The large decoding table is segmented into multiple smaller decoding tables, each corresponding to a specific code sequence length. Instead of searching through one large table containing all possible code words, the system uses multiple small tables that can be queried independently and rapidly, significantly reducing the time required to decode the absolute position.
Solution Approach 2:
The decoding tables are pre-computed and stored in memory during system initialization or manufacturing. This preliminary action allows the runtime decoding process to simply look up pre-calculated values rather than performing complex calculations, reducing decoding time while maintaining high position resolution.
3Measurement precision
If more code elements are arranged in sequence to increase the number of codable positions, then measurement precision is improved, but device complexity increases due to longer code words requiring larger decoding tables
Solution Approach 1:
The long code word is segmented into multiple shorter code sequences of different lengths (e.g., 3, 5, 7 code elements). Each segment is decoded using a corresponding small decoding table, avoiding the need for one large decoding table. This segmentation maintains the ability to encode a large number of positions while keeping the decoding structure manageable and less complex.
Solution Approach 2:
Instead of using a single code sequence that covers the entire measuring range (which would require a very long code word and large decoding table), the patent uses multiple partial code sequences of different lengths that together cover the full range. Each sequence handles a portion of the encoding task, allowing the system to achieve high resolution without the complexity of a single comprehensive code word.
Data Source
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AI summary
An absolute position code (1) is designed as a single-track code. It consists of a plurality of code sequences (A, B) which have different lengths (LA, LB) and which, when combined, absolutely encode a measurement range in an unambiguous manner. For this purpose, code elements of the plurality of code sequences (A, B) are arranged according to a predetermined sequence which forms a segment that in turn is repeatedly arranged one after the other within the measurement range. In order to be able to absolutely encode an as wide a measurement range as possible in an unambiguous manner, each of the segments comprises at least three code elements. In order to determine an unambiguous position (POS) within the measurement range of the position code (1), a decoding device (3) is provided which has a table (TA, TB) for each of the two code sequences (A, B) for decoding. The absolute position (POS) is determined from the obtained partial positions (xA, xB) within the plurality of code sequences (A, B).