scholarly journals Experimental Investigation of Linear Encoder’s Subdivisional Errors under Different Scanning Speeds

2020 ◽  
Vol 10 (5) ◽  
pp. 1766
Author(s):  
Donatas Gurauskis ◽  
Artūras Kilikevičius ◽  
Sergejus Borodinas
Keyword(s):  
Experimental Investigation ◽  
Physical Nature ◽  
Scanning Speed ◽  
Fast Fourier Transformation ◽  
Optical Components ◽  
Optical Scanning ◽  
Speed Test ◽  
Linear Encoder ◽  
Measuring Scale ◽  
Accuracy And Repeatability

Optical encoders are widely used in applications requiring precise displacement measurement and fluent motion control. To reach high positioning accuracy and repeatability, and to create a more stable speed-control loop, essential attention must be directed to the subdivisional error (SDE) of the used encoder. This error influences the interpolation process and restricts the ability to achieve a high resolution. The SDE could be caused by various factors, such as the particular design of the reading head and the optical scanning principle, quality of the measuring scale, any kind of relative orientation changes between the optical components caused by mechanical vibrations or deformations, or scanning speed. If the distorted analog signals are not corrected before interpolation, it is very important to know the limitations of the used encoder. The methodology described in this paper could be used to determine the magnitude of an SDE and its trend. This method is based on a constant-speed test and does not require high-accuracy reference. The performed experimental investigation of the standard optical linear encoder SDE under different scanning speeds revealed the linear relationship between the tested encoder’s traversing velocity and the error value. A more detailed investigation of the obtained results was done on the basis of fast Fourier transformation (FFT) to understand the physical nature of the SDE, and to consider how to improve the performance of the encoder.

Experimental Investigation of an Ultra-High Bypass Ratio Embedded Boundary Layer Ingesting Propulsor for Subsonic Cruise Aircraft

2020 ◽  
Author(s):  
David J. Arend ◽  
John D. Wolter ◽  
Stefanie M. Hirt ◽  
John A. Gazzaniga ◽  
William T. Cousins ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Stability Margin ◽  
Peak Time ◽  
Peak Efficiency ◽  
Speed Test ◽  
Test Conditions ◽  
Bypass Ratio

Abstract An experimental investigation has been completed of the performance and operability of a first of its kind 0.289 scale boundary layer ingesting propulsor within the new 6.5ft × 6ft transonic embedded propulsor testbed of NASA’s 8ft × 6ft Supersonic Wind Tunnel. This propulsor consisted of a coupled inlet and distortion-tolerant fan stage design embedded in a simulated upper aft hybrid wing body aircraft installation. The boundary layer ingesting inlet had a length-to-diameter ratio of 0.67. The distortion tolerant fan was 22 inches in diameter and had a stage pressure ratio of 1.34 and a bypass ratio of 16. The embedded propulsor was evaluated at its Mach 0.78 local freestream conditions. At peak efficiency 100% design speed test conditions, it provided a mass flow weighted inlet total pressure recovery of 96.5% and an adiabatic fan stage efficiency of 87.9%. These values differed meaningfully from the pre-test computational fluid dynamic analysis based design intent. At this operating condition, the effects of inlet-fan coupling extended approximately 0.45 fan diameters upstream into the inlet. The inlet was measured to have a stability margin of approximately 28% and was pre-entry boundary layer separation limited. The fan had approximately 12% of stability margin at 100% corrected speed at which conditions it was flutter limited. It exhibited otherwise flutter free operation over its entire aircraft cruise operating map. Consistently increasing levels of fan stability margin were demonstrated at successively lower fan speeds to in excess of approximately 24% at 80% corrected speed. At each of these reduced speeds, fan stability margin was full annulus stall limited. Inlet airflow distortion remained one-per-rev throughout all tested conditions. At peak efficiency 100% speed test conditions, the boundary layer ingesting inlet airflow had steady state radial and circumferential ARP1420 distortion intensities of 1.2 and 7.2%, respectively. Peak time-variant distortion intensities of 2.3% radial and 8.9% circumferential were also recorded. Comparisons to pre-test computational fluid dynamic predictions are also provided.

scholarly journals Line Beam Scanning-Based Ultra-Fast THz Imaging Platform

2019 ◽  
Vol 9 (1) ◽  
pp. 184
Author(s):  
Huachuan Huang ◽  
Qiao Liu ◽  
Yi Zou ◽  
Liguo Zhu ◽  
Zhenhua Li ◽  
...  
Keyword(s):  
Human Body ◽  
Scanning Speed ◽  
Thz Imaging ◽  
High Quality ◽  
Beam Scanning ◽  
Quality Performance ◽  
Optical Components ◽  
Scanning Angle ◽  
Line Beam ◽  
Scanning Range

In order to realize rapid THz detecting and imaging, a line beam scanning-based ultra-fast THz imaging platform is designed combining simple optical components and lightweight mechanical system. The designed THz imaging platform has the resolution of 12 mm, the scanning angle range of ±10.5°, the scanning speed of 0.17 s/frame, and the scanning range of 2 m × 0.8 m; moreover, it can realize rapid human body THz imaging and distinguish metallic objects. Considering its high-quality performance in THz imaging and detecting, it is believed the proposed line beam scanning-based ultra-fast THz imaging platform can be used in the future in various safe screening applications.

scholarly journals An Analytical and Experimental Investigation of Average Laser Power and Angular Scanning Speed Effects on Laser Tube Bending Process

2017 ◽  
Vol 95 ◽  
pp. 05008 ◽  
Author(s):  
Khalil Ibraheem Imhan ◽  
B.T.H.T. Baharudin ◽  
Azmi Zakaria ◽  
Mohd Idris Shah b. Ismail ◽  
Nasser Mahdi Hadi Alsabti ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Laser Power ◽  
Scanning Speed ◽  
Tube Bending ◽  
Laser Tube ◽  
Average Laser Power ◽  
Bending Process ◽  
Angular Scanning ◽  
Average Laser

EXPERIMENTAL INVESTIGATION OF BOUNDARY LAYER STATE ON THE SURFACE OF HIGH-SPEED TEST VEHICLE MODEL

2019 ◽  
Vol 50 (1) ◽  
pp. 39-52
Author(s):  
Stanislav Sergeevich Alyoshin ◽  
Valerii Nikolaevich Golubkin ◽  
Anatoliy Aleksandrovich Gubanov ◽  
Ivan Valerievich Nazhimov ◽  
Yurii Grigoryevich Shevalev ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
High Speed ◽  
Vehicle Model ◽  
Test Vehicle ◽  
Speed Test

Experimental Investigation on Laser Milling of Al2O3 Ceramic

2013 ◽  
Vol 457-458 ◽  
pp. 160-163 ◽  
Author(s):  
Zhao Mei Xu ◽  
Zong Hai Hong
Keyword(s):  
Experimental Investigation ◽  
Laser Power ◽  
Orthogonal Experiment ◽  
Single Layer ◽  
Scanning Speed ◽  
Circular Cavity ◽  
Range Analysis ◽  
Factors Affecting ◽  
Milling Parameters ◽  
Laser Milling

Milling of Al2O3 ceramic is affected by various factors. Combination of laser milling parameters was optimized based on orthogonal experiment in this study. The affect degree of the parameters on the milling depth was obtained by range analysis ,based on which process parameters were optimized and laser milling experiment was taken on circular cavity using optimized parameters. The results indicated that the sequence of the factors affecting on the milling depth was laser power,scanning speed, overlap amount,defocused quantity successively. By using optimized parameters,milling depth of 0.4mm was obtained for single layer experiment,and milling result was satisfactory. The roughness was increased because the molten on the specimen surface failed to be removed,thus the pressure of the assist huff gas should be increased to improve the surface quality.

Physical Nature of Structure and Properties Degradation of Rail Surface after Long Term Operation

2018 ◽  
Vol 30 ◽  
pp. 39-45
Author(s):  
Victor E. Gromov ◽  
Anton A. Yuriev ◽  
Oleg A. Peregudov ◽  
Sergey V. Konovalov ◽  
Yurii F. Ivanov ◽  
...  
Keyword(s):  
Physical Nature ◽  
Surface Layers ◽  
Term Operation ◽  
Optical Scanning ◽  
Transmission Electron ◽  
Dynamical Recrystallization ◽  
Parameters Measurement ◽  
Diffraction Microscopy ◽  
Electron Diffraction Microscopy

By methods of optical, scanning and transmission electron diffraction microscopy and microhardness and tribology parameters measurement the changes regularities of structure-phase states, defect substructure of rails surface after the long term operation (passed tonnage of gross weight 500 and 1000 mln. tons) were established. It is shown that the wear rate increases in 3 and 3.4 times after passed tonnage of gross weight 500 and 1000 mln. tons, accordingly, and the friction coefficient decreases in 1.4 and 1.1 times. The cementite plates are destroying absolutely and cementite particles of around form with the sizes 10-50 nm are forming after passed tonnage 500 mln tons. The appearance of dynamical recrystallization initial stages is marked after the passed tonnage 1000 mln tons. It is shown that the operation of steel rails is accompanied by full fractures in surface layers with lamellar pearlite grains and the formation of ferrite–carbide mixtures with nanosized particles. The deformation of steel increases the densities of scalar and excess dislocations, the curvature–torsion values of the crystal lattice, and the amplitudes of internal stress fields. The possible mechanisms of established regularities are discussed. It is noted that two competitive processes can take place during rails long term operation: 1. Process of cutting of cementite particles followed by their carrying out into the volume of ferrite grains or plates (in the structure of pearlite). 2. Process of cutting, the subsequent dissolution of cementite particles, transition of carbon atoms to dislocations (into Cottrell atmospheres), transition of carbon atoms by dislocations into volume of ferrite grains or plates followed by repeat formation of nanosize cementite particles.

Detection and Characterization of earth-like Planets

1997 ◽  
Vol 161 ◽  
pp. 299-311 ◽  
Author(s):  
Jean Marie Mariotti ◽  
Alain Léger ◽  
Bertrand Mennesson ◽  
Marc Ollivier
Keyword(s):  
Direct Detection ◽  
Contrast Ratio ◽  
Angular Size ◽  
Physical Nature ◽  
Major Axis ◽  
Infrared Emission ◽  
Space Technology ◽  
Semi Major Axis ◽  
Earth Like Planets ◽  
Visible Wavelengths

AbstractIndirect methods of detection of exo-planets (by radial velocity, astrometry, occultations,...) have revealed recently the first cases of exo-planets, and will in the near future expand our knowledge of these systems. They will provide statistical informations on the dynamical parameters: semi-major axis, eccentricities, inclinations,... But the physical nature of these planets will remain mostly unknown. Only for the larger ones (exo-Jupiters), an estimate of the mass will be accessible. To characterize in more details Earth-like exo-planets, direct detection (i.e., direct observation of photons from the planet) is required. This is a much more challenging observational program. The exo-planets are extremely faint with respect to their star: the contrast ratio is about 10−10at visible wavelengths. Also the angular size of the apparent orbit is small, typically 0.1 second of arc. While the first point calls for observations in the infrared (where the contrast goes up to 10−7) and with a coronograph, the latter implies using an interferometer. Several space projects combining these techniques have been recently proposed. They aim at surveying a few hundreds of nearby single solar-like stars in search for Earth-like planets, and at performing a low resolution spectroscopic analysis of their infrared emission in order to reveal the presence in the atmosphere of the planet of CO H2O and O3. The latter is a good tracer of the presence of oxygen which could be, like on our Earth, released by biological activity. Although extremely ambitious, these projects could be realized using space technology either already available or in development for others missions. They could be built and launched during the first decades on the next century.

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