Absolute Code Scale With Alternating Sequences For Position Encoding
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Solution Overview
Problem
Existing linear position encoder systems face challenges in achieving high precision and accuracy, especially in sub-millimeter or sub-micrometer ranges, while also being susceptible to transverse deviations that can affect measurement accuracy, and require complex analysis and external aids for initialization and compensation.
Innovation Solution
An absolute code scale composed of alternating sections of two different absolute code sequences with distinct phase shifts, allowing for self-initialization and tolerance to thermal expansions, enabling precise position determination without complex analysis and external aids, and accommodating transverse deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a single absolute code sequence is used for position encoding, then the measurement range is limited, but extending the measurement range requires multiple codes which increases system complexity
Solution Approach 1:
The code scale is divided into multiple alternating sections, each section containing a different absolute code sequence (first code sequence, second code sequence, third code sequence). This segmentation allows the system to cover a longer measurement range by switching between different code sequences rather than using one complex long-range code, thereby reducing overall system complexity while extending measurement capability.
Solution Approach 2:
The patent introduces a temporal or spatial dimension to the coding scheme by alternating between different absolute code sequences in successive sections. Instead of using a single complex code that would require complex analysis, the system uses multiple simpler codes in sequence, adding the dimension of code sequence selection to the position encoding process.
2Measurement precision
If high precision position determination is achieved through complex analysis methods, then measurement accuracy improves, but the system becomes more susceptible to interference and requires external aids
Solution Approach 1:
The alternating absolute code sequences are designed to be self-differentiating, allowing the read head to automatically determine which code sequence is present and decode the position information without requiring external initialization aids or complex analysis algorithms. The code structure itself provides the necessary information for self-identification and self-decoding.
Solution Approach 2:
Each section of the code scale has a specific local quality characterized by its unique absolute code sequence. The first section uses a first code sequence, the second section uses a second code sequence, and so on. This local differentiation allows the system to determine position accurately by simply identifying which section is being read and decoding the corresponding code, without requiring complex global analysis.
3Reliability
If the code scale is made tolerant to thermal expansions, then reliability improves, but the position resolution may be compromised
Solution Approach 1:
The patent employs multiple absolute code sequences with different characteristics (different periods, different coding schemes) in alternating sections. This allows the system to change the effective coding parameter being used depending on the section, providing tolerance to thermal expansions through code selection while maintaining position resolution through appropriate code design in each section.
Data Source
AI summary
Some embodiments of the invention relate to an absolute code scale of an angle or linear position encoder, which is composed of a first absolute code sequence having a first primary code period length, which is periodically continued, and at least one second absolute code sequence having a second primary code period length, which is periodically continued. The first and the at least one second absolute code sequence are codeword-foreign in relation to one another in this case.Along the absolute code scale, in each case one section from the first and one section from the at least one second absolute code sequence are successively arranged alternately and in this case the absolute code sequences are each shifted in relation to one another in the different sections from the same absolute code sequence along this arrangement.