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Keywords = optical shaft encoder

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11 pages, 2543 KiB  
Communication
Methods for Comprehensive Calibration of a Low-Frequency Angular Acceleration Rotary Table
by Renjian Feng, Jiaxuan Yan, Yinfeng Wu, Ning Yu and Xudong Yin
Sensors 2023, 23(10), 4876; https://doi.org/10.3390/s23104876 - 18 May 2023
Cited by 2 | Viewed by 1767
Abstract
The total harmonic distortion (THD) index and its calculation methods are presented to calibrate the sinusoidal motion of the low-frequency angular acceleration rotary table (LFAART) and make up the incomprehensive evaluation based on the angular acceleration amplitude and frequency error indexes. The THD [...] Read more.
The total harmonic distortion (THD) index and its calculation methods are presented to calibrate the sinusoidal motion of the low-frequency angular acceleration rotary table (LFAART) and make up the incomprehensive evaluation based on the angular acceleration amplitude and frequency error indexes. The THD is calculated from two measurement schemes: a unique scheme combining the optical shaft encoder and the laser triangulation sensor and a regular scheme using the fiber optical gyroscope (FOG). An improved reversing moments recognition method is presented to upgrade the accuracy of solving the angular motion amplitude based on optical shaft encoder output. The field experiment shows that the difference in the THD values achieved using the combining scheme and FOG is within 0.11% when the signal-to-noise ratio of the FOG signal is higher than 7.7 dB, indicating the accuracy of the proposed methods and the feasibility of taking THD as the index. Full article
(This article belongs to the Special Issue Important Achievements in Optical Measurements in China 2022–2023)
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27 pages, 9295 KiB  
Article
Modal Analysis, Metrology, and Error Budgeting of a Precision Motion Stage
by Ahmet Okyay, Kaan Erkorkmaz and Mir Behrad Khamesee
J. Manuf. Mater. Process. 2018, 2(1), 8; https://doi.org/10.3390/jmmp2010008 - 24 Jan 2018
Cited by 2 | Viewed by 7196
Abstract
In this study, a precision motion stage, whose design utilizes a single shaft supported from the bottom by an air bearing and voice coil actuators in complementary double configuration, is evaluated for its dynamic properties, motion accuracy, and potential machining force response, through [...] Read more.
In this study, a precision motion stage, whose design utilizes a single shaft supported from the bottom by an air bearing and voice coil actuators in complementary double configuration, is evaluated for its dynamic properties, motion accuracy, and potential machining force response, through modal testing, laser interferometric metrology, and spectral analysis, respectively. Modal testing is carried out using two independent methods, which are both based on impact hammer testing. Results are compared with each other and with the predicted natural frequencies based on design calculations. Laser interferometry has been used with varying optics to measure the geometric errors of motion. Laser interferometry results are merged with measured servo errors, estimated thermal errors, and the predicted dynamic response to machining forces, to compile the error budget. Overall accuracy of the stage is calculated as peak-to-valley 5.7 μm with a 2.3 μm non-repeatable part. The accuracy measured is in line with design calculations which incorporated the accuracy grade of the encoder scale and the dimensional tolerances of structural components. The source of the non-repeatable errors remains mostly equivocal, as they fall in the range of random errors of measurement in laser interferometry like alterations of the laser wavelength due to air turbulence. Full article
(This article belongs to the Special Issue Precision Manufacturing)
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