Angular Minutes Research Articles

Improvement of the method of verification of the drift of the gyrovertical on the UAV during aerial photography using the liquid horizon

The analysis of literary sources and patent documentation showed that among the means of orientation of UAVs in space, systems based on fibre optic gyroscopes have the highest accuracy, which allow determining the pitch and roll values of UAVs with an accuracy of 1.2ʹ-3ʹ. A negative feature of UAV navigation systems in space is the instability of vertical reproduction over time, characterized by its drift.To reduce the influence of the drift of the main vertical sensor, there is its verification by an additional true vertical sensor based on the liquid horizon. At the level of the invention, the gyrovertical verification method has been improved for the use on moving objects intended for shooting, in particular on UAVs. The verification method is implemented by a device based on an optical-electronic liquid horizon, which allows to increase the accuracy of reproduction of the true vertical in comparison with the analogue by about 2 times. The formulas for calculating the dimensions of the hermetic ampoule of the optical-electronic unit for measuring the position of the liquid horizon are given, depending on the sensitivity of the reproduction of the true vertical. A mathematical rationale for determining the position of the dynamic equilibrium of the liquid surface during its damping oscillations in a hermetic ampoule in areas of uniform and rectilinear movement of the carrier of the filming equipment is given, which contributes to increasing the reliability of its determination. As a result, it is possible to verify the drift of the main gyrovertical sensor in angular minutes. Implementation of the development will contribute to increasing the accuracy of obtaining coordinate information using moving carriers of filming equipment, in particular, UAVs equipped with mechanical or fibre-optic gyroscopes.

Analysis of real-world visual ergonomics at the visual display unit.

In this interventional study, the ergonomic workplace set-up and the impact of character size on subjectively estimated working productivity and computer vision syndrome (CVS) were evaluated in the field. The number of displays and their size, resolution, surface structure, position in the room and relation to the eye were evaluated for 152 units. CVS was assessed using the CVS-Questionnaire. Habitually used character size for an uppercase E was recorded and compared to the ISO 9241-303:2011, national standards (e.g., ANSI/HFES 100-2007) and national guidelines (e.g., German DGUV Information 215-410). In case of failure to comply with these standards, character size was increased to 22 angular minutes to reach the recommended ranges. Reasons for returning to former or smaller character sizes were recorded, and subjectively perceived changes in productivity were estimated by the participants using a visual analogue scale before and 2 weeks after the intervention using a questionnaire. The average visual display unit consisted of two non-glare (matt) 24″ widescreen monitors that were located approximately 73 cm (primary) and 76 cm (secondary) from the eyes. The mean (SD) habitually set character size was 14.29 angular minutes (3.53) and therefore both statistically and clinically significantly too small compared with ISO 9241-303:2011 (p < 0.001). Increasing the character size to 22 angular minutes produced a 26% reduction in subjectively rated productivity (p < 0.001). No significant correlation between character size and symptoms of CVS was demonstrated. In the workplaces investigated, recommendations for character size were not adhered to. This resulted in a reduction in productivity and was not compatible with some of the work requirements, for example, obtaining a broad overview of a spreadsheet.

ADJUSTMENT OF LARGE SOLAR OVEN FLAT HELIOSTAT HELIOSTATS

This paper presents an improved method for adjusting individual mirrors –facets of heliostats of a Big Solar Furnace (BSF) with a heat output of 1000 kW in Uzbekistan. Due to the fact that a BSF consists of 22,790 pieces of individual mirrors, the adjustment - setting a specific geometric position of these mirrors is very important. The process of adjusting the mirrors is very time consuming and lengthy. Often exactly the adjustments are influenced by subjective factors by the aligners. In order to improve the performance and accuracy of the alignment, the facet of heliostats has applied the Technical Vision System (TVS), as well as improved the process of assessing the state of alignment and the processing of alignment data. The TVS consisting of a video camera, an interface, a personal computer and special software allows you to visually and accurately assess the alignment conditions of the heliostat facets before and after the alignment process. Allows you to save the data in computer memory for further processing and analysis. Allows you to create a database of the alignment status of each of the 62 heliostats of LSF. Special software developed by us allows you to quickly and accurately determine the deviations of the heliostat facets from the calculated geometric points in angular minutes. Based on the data obtained, you can build histograms, graphs, etc. for visual analysis of the heliostat alignment states before and after the alignment process.

Synchronous Software Control over 62 Heliostats for Enhancing Function Capabilities of a Big Solar Furnace

A comparative analysis of the performance accuracy of the tracking systems of process and energy heliostats was carried out based on the long-term experience of operating a two-mirror big solar furnace (BSF). It is shown that a new additional automatic control system (ACS) is being developed for the upgrade intended to expand the function capabilities of the BSF. The automated control system must maintain dynamics while simultaneously tracking the intersection of two axes of elliptical optical images of the Sun or other celestial objects in the focus of the concentrator from all 62 heliostats simultaneously. In addition, the software-based ACS in development should maintain the previously embedded functions of the automatic temperature control system (ATCS) with the departure of the center of elliptical optical images from all 62 heliostats within 25 angular minutes in order to expand the zone of uniform density. It is proven that the newly developed system of software-based management of heliostats must expand their function capabilities. The optical and geometric parameters (manufacturing accuracy, focal length, and aperture angle) of this installation allow using the solar installation as an astronomical telescope with a midsection size of 42 × 54 m2 for registering secondary Cherenkov radiation from gamma-ray sources in the night sky, creating a favorable zone for obtaining a powerful stream of laser beams, as well as efficiently synthesizing molecular hydrogen by thermolysis and electrolysis. It is shown that the automatic software control packages already created or in the process of being created must synchronously and regularly ensure the coincidence of centers of the Sun’s optical images, which have their own variable shapes and densities, depending on the value of the aperture angle with the focal point of the concentrator, for each of the 62 heliostats.

Angular Stability Control System for Linear Pie-Zoelectric Motor

The paper is devoted to the system for measuring the stability of the angles Yaw (θz), Pitch (θy) and Roll (θx) of a linear piezoelectric motor type LPM5 / BSP-1540SL, which allowed to measure the angular deviations of the piezoelectric carriage depending on its position. The system was based on the use of the auto-collimation method, which provided the measurement of the angular discrepancy between its own optical axis of the auto-collimator and the normal to the plane of the mirror-reflecting surface. To measure the angular deviation of the carriage of the engine was used AK-0,5U auto-collimator with an optical resolution of 0.5 arc seconds. The auto-collimator scale was marked up in steps of 0.5 arcmin (30 arcsec), and its informative optical reference was made as a green intersection. This feature was later used to determine its position on the image obtained with the CCD matrix OV5647. The image obtained from the matrix had a resolution of 1024x768 pixels. In the matrix image, the distance between adjacent labels (auto-collimator scale step) was ~ 35 pixels, that is, the electronic resolution of the matrix was near to ~ 1 arc second. For control the engine speed and its position was used an optical encoder iC-PX3212 with a resolution of 2.6 µm. The control system also includes a single-board computer RaspberryPi 3B + , which allowed to control the engine via USB data protocol, receive images via MIPI-CSI protocol, process images from the array, and output it to the monitor via HDMI. During the experiment, 376 images were obtained (188 images when measuring Pitch, Yaw angles, and 188 images when measuring Roll angle). Image processing was performed using PIL (image) and numpy libraries in Python programming language. Was demonstrated the possibility of measuring angular stability over a large distance of movement with an accuracy of 5 arc.sec. On the basis of the experimental results obtained, it was found that most changed the angles of Pitch and Roll (~ 3 angular minutes). The results obtained by measuring the angles of Pitch, Yaw and Roll make it possible to develop a model of errors of a multi-axis micromanipulation system in order to take them into account when designing the control system.

Features of the Spectral Characteristics of Narrow-Band Optical Filters with Oblique Incidence of the Radiation Beam

The performance of narrow-band optical filters on the basis of frustrated total internal reflection was analyzed taking into account the Gaussian distribution of the angle of radiation incidence. The spectral characteristics of these optical filters are modelled with and without divergence of the incident beam. It is shown that, when measuring the spectral characteristics of optical filters, the divergence of the incident radiation beam should not be greater than a certain limit value that does not exceed several angular minutes.

Особенности спектральных характеристик узкополосных светофильтров при наклонном падении пучка излучения

Spectral characteristics of narrow-band optical filters based on frustrated total internal reflection is analyzed considering the Gaussian distribution of angle of incidence. The spectral characteristics were calculated with and without incident beam divergence. We showed that when the spectral characteristics of these optical filters is measured, the incident beam divergence should not exceed a certain limit value, which is a few angular minutes.

РЕЗУЛЬТАТИ ФОТОМЕТРИЧНОГО ОПТИЧНОГО МОНІТОРИНГУ ЧОТИРЬОХ АКТИВНИХ ЯДЕР ГАЛАКТИК У 2018–2019 РОКАХ

Active galactic nuclei (AGN) are a source of very high energies. Blazars are a subclass of active galactic nuclei that can be observed in the optical spectral range. The aim of the study is some BL Lacertae type blazars, which are characterized by a non-emission optical spectrum and exhibit brightness variations at all wavelengths. The results of systematical monitoring of selected objects from the CTA (Cherenkov Telescope Array) optical follow up list, started in January 2018 are presented. The observations are carried out with the AZT-8 (D = 70 cm, F = 2.8 m) telescope of the observation station Lisnyky of Taras Shevchenko National University of Kyiv. In 2018 the telescope AZT-8 was included in the list of supporting instruments in the CTA consortium. The AZT-8 equipped with the PL4710-1-BB-E2V CCD (1027×1048 pixels, 13×13 µm/pixel, scale is 0.95 “/pixel, field of view is 16.2 angular minutes) and broadband Johnson/Bessel UBVRI filters. For processing the software Maxim DL was used. During processing accounting of substrate (bias), dark current, flat-field were taken into account. The fluxes of energy from objects of research with the help of standard stars has been turned into visible stellar magnitudes. Light curves for four objects: 1ES 1011+496, PKS 1222+216, 1ES 1426+428, PKS 1510-089 were plotted. Variability of color indexes with time was investigated. In addition, we determined the variability amplitude and tested all these objects for Intraday Variations (IDV), Short (STV) and Long term variability (LTV) where it was possible. A short-term brightness change (STV) with an amplitude of 0.5 to 1 in all filters (UBVRI) of the Johnson/Bessel system for AGN 1ES 1011+496, PKS 1510-089 was determined. For objects 1ES 1426+428 and PKS 1222+216, the brightness variations do not exceed the total error (instrumental and methodical). The total error is ∆Σ ≈ 0.060.1 magnitude.

Horizon Line Stability Observations over the Sea

Increasing the stability and reliability of navigation for mobile objects of different classes is becoming increasingly significant. Satellite navigation systems have a fundamental defect: a vulnerability to hacking and spoofing. Observation of the horizon line is significant for two applications. The first is stellar inertial navigation systems. In this case, the horizon line can be used for local vertical estimation. Errors in local vertical estimation directly affect coordinate errors. The second is correlation-extremal navigation based on the observed horizon line shape (when islands or continents are observed from aerial vehicles). In both cases, instability of the horizon line produces navigation errors. A measurement procedure for horizon line position estimation was proposed and realised. Around-the-clock horizon line shooting was undertaken in 2013. Processing of the results shows a horizon line direction instability of about 5–7 angular minutes during the day time.

Применение глобальных моделей гравитационного поля для обработки высокоточного нивелирования

The article studies the properties of the high-degree gravity field model EGM-2008 in the calculation of integral characteristics at large distances several times greater than the spatial resolution of the model. As an example of an indirect evaluation of a high-degree model, a gravimetric correction was computed into the sum of the measured elevations along the line of the high-precision I class leveling of the Krasnovodsk – Chardzhou line located in Turkmenistan. Using the calculator ICGEM, the Bouguer anomalies were calculated at each point of the line, then the attraction of the Bouguer layer (used heights are from catalog) excluded for the transition to free-air anomalies. In parallel, for a direct evaluation of the model, a regular grid of Bouguer anomalies with a step of 2 angular minutes within line area was also obtained, which were then compared with the anomalies from the gravity map J-40 of scale 1

Subgrain boundaries in single crystal blade airfoil of aircraft engine

The single crystal turbine blades of aircraft engine were obtained by directional solidification of Ni‐based superalloy via Bridgman technique at withdrawal rate of 5 mm/min. The CMSX‐4 industrial alloy were used for crystallization. After crystallization the blades were subjected to heat treatment. The Laue diffraction, X‐ray diffraction topography and SEM methods were used to investigate the subgrain structure of blade airfoils. It was stated that subgrain boundaries with the misorientation angle ranging from over a dozen to a few dozen angular minutes occurred in the airfoil. The number of low‐angle boundaries in the cross‐section near the tip of the blade airfoil is higher than that in the cross‐sections located near the root area. It is caused by formation during crystallization of additional low‐angle boundaries in thin‐walled airfoil area and their propagation toward the tip of airfoil. The number of low‐angle boundaries in cross‐section located near the tip of airfoil can be determined by three mechanisms: dendrites “deflection” on surface of mould; creation of internal stress regions in the thin‐walled area of blade airfoil and propagation of two additional boundaries from root to the airfoil.

Implementation of an algorithm for determining the spatial coordinates and the angular orientation of an object based on reference marks, using information from a single camera

An algorithm for determining the spatial coordinates and angular orientation of an object with reference emitters using a single calibrated camera is considered. The algorithm is based on a sequential solution of a perspective-four-point task and more precise definition of reference emitter’s spatial coordinates using the Levenberg – Marquardt optimization method. It is shown that while in the camera field of view there are four reference emitters with a priori known distances between them measured with up to 0.15 mm precision, it is possible to determine the angular orientation of the object in real time with an error less than 20 angular minutes.

J27 System For Assessment Of The Visual Smooth Pursuit Impairment In Huntington Disease

<h3>Background</h3> During the development of Huntington disease smooth pursuit may become impaired, decreasing the gain of the pursuit and releasing the saccadic intrusions. Although UHDRS includes the pursuit evaluation, it estimates the performance of this oculomotor function only qualitatively. Meanwhile its quantitative evaluation without eye movement recording equipment is practically impossible. It barely allows to notice large saccadic intrusions and it cannot detect reduction of the gain. Furthermore UHDRS motor score uses four point scale to assess the pursuit, rating it from “normal”, through “jerky”, “incomplete range” and “cannot pursue”. Such a subjective method strongly depends on examiner’s skill and experience. <h3>Technique</h3> We designed the system that allows objective measurement of smooth pursuit parameters and its quantification. Additionally, the immobilisation of the head usually required in studying smooth pursuit is unnecessary. The sensor is placed on the subject’s head along with the laser servo projector mounted on forehead plate allowing for viewing the moving target on the wall. Eye movement measuring system uses infrared reflectometry, providing high temporal and spatial resolution (1kHz, 5 angular minutes). Such a device, along with accompanying custom-designed software, allows automatic detection of saccadic intrusions as small as 1 degree. <h3>Conclusions</h3> The developed instrumentation demonstrated the capability for immediate and quantitative assessment of the smooth pursuit quality. Furthermore, it is characterised by easy application and minimal intrusiveness.

Algorithms for Embedded Controllers in Microgyros

Usage of micromechanical gyros (MMG) in space systems is restricted due to their low precision. For this reason development and investigation of methods and algorithms of increasing the precision is a very important problem. Studies have shown that the usage of firmware control in inertial units allows modification of parameters of gyros in the course of their maintenance. Such estimate allows increasing precision of inertial measurement considerably. The paper presents a method and an algorithm for increasing the accuracy of micromechanical gyroscopes. The method is based on using the Kalman filter for estimation of motion of sensing mass relative to the output axis. This estimation is very effective because deflections of sensing mass relative to the output axis are small in practice (on the order of several angular minutes for micromechanical gyros RR scheme). For this reason the level of noise in the measurements is very significant. The paper presents a result of investigations of ability to use Kalman filter for estimating parameters of MMG and the angular rate of the mobile craft in which this gyroscope is installed. Results of simulation are given and issues of implementation are considered.

A predictive model of geosynchronous magnetopause crossings

The experimental data on GOES magnetic measurements and plasma measurements on LANL geosynchronous satellites is used for selection of 169 case events containing 638 geosynchronous magnetopause crossings (GMCs) in 1995 to 2001. We study the necessary conditions for the geosynchronous magnetopause crossings using scatter plot of the GMCs in the coordinate space of Psw versus Bz. In such representation the upstream solar wind conditions demonstrate sharp envelope boundary under which no GMCs are occurred. The boundary has two strait horizontal branches where Bz does not influence on the magnetopause location. The first branch is located in the range of Psw=21 nPa for large positive Bz and is associated with an asymptotic regime of the pressure balance. The second branch asymptotically approaches to the range of Psw=4.8 nPa under very strong negative Bz and it is associated with a regime of the Bz influence saturation. We suggest that the saturation is caused by relatively high contribution of the magnetosphere thermal pressure into the pressure balance on the magnetopause. The intermediate region of the boundary for the moderate negative and small positive IMF Bz can be well approximated by a hyperbolic tangent function. We interpret the envelope boundary as a range of necessary upstream solar wind conditions required for GMC in the point on the magnetopause located mostly close to the Earth ("perigee" point). We obtain that the dipole tilt angle and dawn-dusk asymmetry influence on the "perigee" point location. We find that the aGSM latitude of this point depends linearly on the dipole tilt angle with the slope about -0.5. The aGSM longitude of the "perigee" point decreases with IMF Bz with a rate of about 2 angular minutes per 1 nT. An empirical model predicting the magnetopause crossing of the geosynchronous orbit in the "perigee" point is proposed.

On sun tracking accuracy of concentrators

For exact and inexact concentrators, the influence of the accuracy of Sun tracking on the characteristics of the concentrated spot was investigated. It was found that, for solar furnaces, the tracking accuracy can be no higher than 4 angular minutes and, for solar energy facilities, it can be no higher than 7 angular minutes.

Construction of Telescope Inaccuracy Model According to Data of Satellites Laser Ranging

The method of constructing error model of pointing the telescope to the target is present in the article. It bases on using the angular encoders data (azimuth and elevation). This angles are fixed in time in the satellite laser ranging. The data is presented in the codes of angles (in inside frame) and the moments of time, in which they are fixed. The consistence of procedures and result of received model are presented in article. Also advantages and disadvantages of the new model are considered in comparison with the method of stars observers. The method tested on the 40 passes of the satellites. The model constructing in station “Kyiv-Golosiiv” in 2003 year is used for the comparison.[1]. The accuracy of this model is on the level 15 arcsec. TARGET SETTING For successful observation of any object it is necessary to point at it instrument, with a help of which we will do observation and track it with necessary accuracy during all necessary time. Accuracy of pointing and tracking depends on type of observations and can be changed from dozens of angular minutes to fractions of angular seconds. So, the higher accuracy of pointing and tracking we need the more careful we will study and take into account reasons, which lead to inaccuracy. It was always paid much attention to the questions of construction of telescope inaccuracy model. It is necessary to pay attention to some of the following works [1]-[4]. For example, for radio-telescopes which function in VLBI network, created standard complex of software for observation of radio sources with aim of defining more precisely of telescope model parameters, because these radio-telescopes function under total control of computer, that is in automatic regime. Tendency of development of SLR technique directed to creation of automatized systems that can do observation of satellites in semiautomatic and automatic regimes. For this purpose it is necessary to provide accuracy of pointing by laser beam at observed object and make it’s tracking with accuracy that does not exceed a half of beam width. Reasons of not accurate laser beam pointing at satellite can be inaccuracy in telescope assembling and searching ephemeris. Inaccuracy in searching ephemeris can be compensated by moving calculated position of satellite along orbit. This correction can be done automatically during observation session changing “ephemeris” time of observations since we get reflected from satellite signals. More than that, at regular observations we can determine corrections to searching ephemeris ARTIFICIAL SATELLITES, Vol. 41, No. 3 2006 DOI: 10.2478/v10018-007-0010-8 Unauthenticated Download Date | 6/20/16 7:16 AM

Multi-viewing zone screen for multiview 3-D displays

A new type of multi-viewing zone screen for multiview 3-D display is described. The screen is made by stacking a Fresnel lens and a reflective prism array plate. The screen performs both focusing and beam dividing functions and directs very narrow light beams to three viewing zones for three spectators. The results of experimental testing of the screen have demonstrated that current technology of Fresnel lens and prism grooves on PMMA(Ploymethyl Methacrylate) allows manufacture of screen having a pixel size of about 1-2 mm. This size is reasonable enough for a screen with dimensions about 1m size. Optical qualities of Fresnel lenses and grooved prism arrays achieve an angular resolution for the screen of several angular minutes.

Experiments on meso-optical fourier transform microscope with double focusing

There are described two experiments on meso-optical Fourier transform microscope with double focusing, one with nuclear emulsion, exposed by the accelerated Ne-nucleus, and another, in which the primary particles were the accelerated Oxigen-nucleus. It is shown that the measurement error of the orientation angle θ xy is equal to ±1.5 angular minutes. Three kinds of the geometrical distortions in the nuclear emulsion have been detected.

X‐ray two‐crystal diffractometer for testing of plane analyser crystals

AbstractA two‐crystal diffractometer (TCD) for testing the mosaic structure of LiF crystals is presented. Peculiarities are the adapted sensivity (angular minutes), short measuring times, large registered areas and the possibility of application for various kinds of surface treatment.