Absolute Rotary Encoder Decentering Correction
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Solution Overview
Problem
Conventional absolute rotary encoders face challenges in accurately detecting absolute positions due to decentering issues, which limit their mounting range and accuracy.
Innovation Solution
The proposed solution involves a reflective optical absolute rotary encoder with dual sensors and processors that generate and process two-phase pseudo sine wave signals from periodic patterns with different pitches, allowing for decentering correction and expanding the attachment allowable range by averaging position signals from multiple sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional absolute rotary encoder uses single sensor reading, then device complexity is low, but measurement precision deteriorates due to decentering errors
Solution Approach 1:
The scale is divided into multiple tracks (first track and second track) with different periodic patterns. Each track is read by a dedicated sensor, allowing independent processing of decentering components from each track and improving overall measurement precision through segmentation of the measurement function.
Solution Approach 2:
Multiple sensors reading different tracks are combined through signal processing. The processor combines the first and second periodic signals to generate corrected position signals that cancel decentering errors, merging multiple measurement sources to achieve higher precision.
2Measurement precision
If decentering correction is implemented, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system extracts decentering components from the periodic signals and uses this feedback information to correct the position measurements. The processor continuously monitors the signals, identifies decentering patterns, and applies corrections to maintain measurement precision.
Solution Approach 2:
The invention changes the parameters of the periodic patterns by using multiple tracks with different periods and phases. This allows the system to distinguish between true position changes and decentering effects, enabling correction without significantly increasing processing complexity.
3Adaptability or versatility
If multiple sensors with different periodic patterns are used, then adaptability expands, but device complexity increases
Solution Approach 1:
The encoder system is designed to handle multiple reading scenarios through universal signal processing. The same processor handles both single-track and multi-track reading modes, and can accommodate different periodic patterns, making the system adaptable to various mounting conditions while using a unified processing approach.
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 effectively corrects decentering errors and enhances the accuracy of absolute position detection, thereby expanding the mounting range and reliability of the encoder.
Implementation Method 1
a first sensor and a second sensor which read first and second tracks, respectively, the first and second sensors being arranged in a radial direction to face each other
Implementation Method 2
generates a first position signal based on first and second periodic signals based on a signal obtained by reading the first and second tracks by the first sensor
Data Source
Figure 1
Figure 2~3
Figure 4A~4C
AI summary
An encoder comprises first and second sensors which reads first and second tracks, the first and second sensors being arranged in a radial direction to face each other, and a processor which generates a first position signal based on first and second periodic signals based on a signal obtained by reading the first and second tracks by the first sensor, and generates a second position signal based on third and fourth periodic signals based on a signal obtained by reading the first and second tracks by the second sensor, wherein the processor generates an absolute position signal indicating an absolute position of at least one of the scale, the first sensor, or the second sensor based on the first and second position signals and the first and third periodic signals.