Methods for Reducing Subdivision Error within One Signal Period of Single-Field Scanning Absolute Linear Encoder
Fan Yang1,2, Xinji Lu3, Artūras Kilikevičius4
1Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
Sensors (Basel, Switzerland)
|January 21, 2023
Summary
Researchers reduced subdivision error (SDE) in absolute linear encoders by 38% using novel Moiré fringe and phase shift methods. This improves positioning accuracy and low-velocity control in CNC machines.
Area of Science:
- Metrology
- Optical Engineering
- Control Systems
Background:
- Absolute linear encoders are crucial for precise displacement measurement in advanced CNC machines.
- Subdivision error (SDE) significantly impacts positioning accuracy and low-velocity control in these systems.
Purpose of the Study:
- To investigate the working principle of absolute linear encoders.
- To propose and validate methods for reducing SDE in absolute linear encoders.
Main Methods:
- Developed a single-field scanning method utilizing shutter-shaped Moiré fringes.
- Implemented a phase shift technique for index grating to suppress harmonics.
- Established a dedicated SDE measuring device for constant-speed measurements.
Main Results:
- Reduced SDE from ±0.218 μm to ±0.135 μm, a 38.07% improvement.
- Fast Fourier Transform (FFT) analysis confirmed effective suppression of third-, fifth-, and seventh-order harmonics.
- Validated the efficacy of the proposed methods in enhancing encoder performance.
Conclusions:
- The proposed methods significantly reduce subdivision error in absolute linear encoders.
- Improved SDE leads to enhanced positioning accuracy and better low-velocity control in CNC applications.
- Harmonic suppression is key to achieving higher precision in optical encoder systems.
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