Absolute Position Detection with Error Correction for Encoders
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Solution Overview
Problem
Existing Vernier type absolute encoders fail to accurately calculate absolute positions when motes and scratches are present on the scale, leading to erroneous detection signals and incorrect position calculations.
Innovation Solution
A position detecting apparatus with a scale featuring multiple pattern arrays of different cycles, an obtaining unit for signal acquisition, a first deriving unit for temporal position calculation, a second deriving unit for displacement measurement, and a determinator that compares differences in temporal positions and displacement amounts to determine the accurate position, thereby preventing erroneous calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Vernier type absolute encoder uses multiple pattern arrays with different pitches for absolute position detection, then measurement precision is improved, but reliability deteriorates when motes and scratches are present on the scale
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the consistency between incremental position changes and absolute position calculations. When a discrepancy is detected (indicating erroneous detection due to motes or scratches), the system flags the absolute position calculation as unreliable and uses only incremental positioning until the next valid absolute reference is obtained. This feedback loop resolves the contradiction by dynamically adjusting which measurement method is trusted based on real-time signal quality.
Solution Approach 2:
The patent performs preliminary validation of detection signals by comparing incremental position changes with absolute position differences before accepting absolute position data. The system pre-checks whether the difference in absolute positions between two points matches the integrated incremental displacement, and only accepts absolute position calculations that pass this validation. This preliminary action prevents erroneous data from corrupting the positioning system while maintaining high measurement precision when conditions are favorable.
2Measurement precision
If encoder operates at low speed to avoid erroneous detection in incremental measurement, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The patent dynamically switches between incremental and absolute positioning modes based on real-time speed conditions and signal quality. At low speeds where incremental measurement is reliable, the system uses incremental mode for continuous high-resolution tracking. At high speeds where incremental measurement may err, the system transitions to absolute positioning with validation. This dynamic adaptation resolves the contradiction by optimizing the measurement method according to operational conditions rather than being constrained to a single speed regime.
Data Source
AI summary
A position detector, includes: a scale having pattern arrays formed in different cycles in a movement direction an obtaining unit which obtains signals in accordance with the pattern arrays; a first deriving unit which derives a temporal position of the scale relative to the obtaining unit based on the signals; a second deriving unit which derives a displacement amount of the scale relative to the obtaining unit based on one or more signals of the signals; and a determinates which determines a determined position of the scale relative to the obtaining unit based on the temporal position and the displacement amount, wherein the determinator determines the determined position based on a result of comparison between a difference between first and second temporal positions respectively calculated by the first and second deriving units at first and second positions and a displacement amount from the first position to the second position.