Method for the numerical evaluation of the color rendering quality of matrix photodetectors

To objectively evaluate the color image of an architectural object when changing its spectral quality and luminance in lighting, it is necessary to ensure its accurate fixation. The measurement of the color coordinates of an object provides the fully capture of its appearance, but this does not allow to get an adequate evaluation of the visual impression without visualizing the lighting scene. This requires a thorough procedure of reproducing the same color coordinates for each point of the image and the object with the same angular coordinates. In this work, an attempt is made to develop a numerical criterion for evaluating the quality of color rendering of the camera as a fixer of color visual impression of the selected scene. The development of a numerical detailed method for evaluation of the quality of color rendering of cameras will allow capturing more reliably such a subjective concept as the correspondence of the visual impression of the real scene and the image file of this scene. The digital format, which contains information about the object, avoids the problems associated with aging of the image. The proposed method of developing ways to numerically evaluate color distortion in photography is considered on the example of digital cameras Nikon D300s, Sony DSC-H5. The described approach for the case of known spectral characteristics allows to unambiguously link the calculated reaction of the camera with the chromaticity coordinates of spectrally pure colors. Modern methods of evaluating the quality of light sources (IES TM-30-15) allow evaluation of the direction of the shift. The proposed indicator – graph E (λi) numerically characterizes the difference between the reaction of the camera and the reaction of the human eye and does not give an idea in which direction there is a difference, conditionally red or blue image compared to the natural scene, but is the simplest and most understandable to the untrained user. It is shown that with an accuracy of measuring spectral characteristics of 1% for the considered example with Nikon D300s, this indicator at different wavelengths is calculated with an uncertainty of not more than 0.002.

INCREASE IN ACCURACY OF MEASURING AIR OBJECTS ANGULAR COORDINATES DURING MULTICHANNEL RECEPTION OF RADIO-LOCATION SIGNAL

Radars with a phased array antenna (PAA) which performs multi-channel radar signal reception are effective means of obtaining radar information about air objects in difficult conditions of air and jamming environment. Radar surveillance for radars with PAA is accompanied by a significant negative effect of tropospheric inhomogeneity, which causes a decrease in the accuracy of measurements of azimuth angles and air object‟s position due to fluctuations of the phase front of the received wave reflected from an air object. According to the results of research, the hypothesis of a normal distribution law of these fluctuations is accepted. The paper presents the results of estimating the root mean square errors of measuring the angular coordinates of the air object, which occur if the fluctuations of the phase front of the received signal‟s wave are not taken into account and analyzes the possibility of reducing such errors when the fluctuations are considered. The possibility of optimizing the angular measurements of air objects in digital radars with PAA is shown, which consists in taking into account the fluctuations of the phase front of the received signal in the algorithm of discrete (fast) Fourier transform, which is widely used to provide spatial measurements in modern digital radar stations. The results of previous studies were generalized, which makes it possible to evaluate the possibility of increasing the accuracy of angular measurements of air objects during multichannel reception of a radar signal in difficult conditions of radar operation.

Quality of Radar Direction-Finding via Conical Scanning

Introduction. Conical scanning is applied for optimizing hardware resources in new devices, as well as when upgrading existing systems. All this explains the relevance of studying this type of direction finding systems.Aim. To adjust and complement the known calculation relations for the variance of direction finding results – an indicator of the quality (accuracy) of direction finding, as well as to determine the possibilities of optimizing direction finding and automatic object tracking processes.Materials and methods. Factors limiting the accuracy of direction finding via conical scanning were analyzed using spectral analysis. Mathematical modeling followed by statistical processing of quantitative results makes it possible to determine the conditions under which the influence of certain factors is predominant, as well as the conditions under which adjustment (completion) of the known calculation relations is required. The specified conditions are the errors at which the objects of direction finding are tracked. New calculation relations for the mentioned adjustment were determined by the methods of statistical radio engineering.Results. The validity of the calculation relations found is confirmed by mathematical modeling. Calculations and modeling lead to the need to optimize parameters for automatic object tracking systems.Conclusion. The study shows that, when choosing parameters for auto-tracking systems with conical scanning, it is important to implement object tracking not with minimal, but rather with optimized tracking errors in angular coordinates, which are to be estimated during direction finding. Moreover, the optimized errors (the values of static errors and the most probable values of the dynamic tracking errors) will require adjustment of the known analytical estimates for the variance of the direction finding results – the qualitative indicator of the direction finder (accuracy indicator). The determined analytical relationships allow such an adjustment to be performed, leading to an increased variance estimate by 10 dB.

A Novel Family of Exact Nonlinear Cascade Control Design Solutions for a Class of UAV Systems

In this work, a novel family of exact nonlinear control laws is developed for trajectory tracking of unmanned aerial vehicles. The proposed methodology exploits the cascade structure of the dynamic equations of most of these systems. In a first step, the vehicle position in Cartesian coordinates is controlled by means of fictitious inputs corresponding to the angular coordinates, which are fixed to a combination of computed torque and proportional-derivative elements. In a second step, the angular coordinates are controlled as to drive them to the desired fictitious inputs necessary for the first part, resulting in a double-integrator 3-input cascade control scheme. The proposal is put at test in two examples: 4-rotor and 8-rotor aircrafts. Numerical simulations of both plants illustrate the effectiveness of the proposed method, while real-time results of the first one confirm its applicability.

Analysis of the stability of automatic tracking of super maneuvering air objects by radio technical tracking systems of the multichannel radar

Multichannel tracking radars with phased antenna arrays are widely used to track air targets. The use of a phased array in combination with digital computing technology allows to control the radar radiation pattern and track several targets in the time distribution mode. Air target tracking in a multichannel radar is provided by subsystems for measuring range, radial velocity and angular coordinates, in most cases, without adaptation to the external influence characteristics. When tracking supermaneuverable air targets, such as 5th and so-called 4++ generation fighters, there is a decrease in the accuracy and stability of tracking relative to the area without maneuver. If the tracking system algorithms are tuned to a low intensity of maneuvering or its absence, a significant increase in the error of tracking the aircraft in the maneuvering section will lead to disruption of auto tracking due to a significant dynamic component of the error. The stability of auto-tracking of maneuvering targets by subsystems of range, radial velocity, and angular coordinates with fixed parameters for the case when the setting of the parameters of the tracking system algorithms coincide with the characteristics of the external influence is analyzes in the paper. The influence of the observation model parameters, the stochastic model of the target movement with exponentially correlated values of the target acceleration, and the measurement period of the target coordinates on the potential tracking accuracy by radio technical tracking systems of the multichannel radar is investigated. To assess the stability of auto-tracking, it is proposed to use the equivalent aperture size of the discriminating characteristic. The influence of the parameters of the target movement stochastic model, the observation model, and the measurement period of the target coordinates on the stability of auto-tracking in terms of range, radial velocity, and angular coordinates is estimated. It is shown that the "weak link" is the radial velocity tracking system. As a result of the research carried out, it becomes possible to further assess the feasibility of adapting the auto-tracking systems to the target maneuvering characteristics and to develop recommendations for choosing the measurement period of the target coordinates.

Identification of maneuvering objects during structural and system control of airspace

Работа посвящена построению процедуры идентификации маневрирующих объектов с использованием критерия идеального наблюдателя и фильтрации параметров трасс при сопровождении средствами мониторинга в интересах структурносистемного контроля воздушного пространства. Для минимизации среднеквадратических ошибок оценок координат и скоростей движения объектов разработаны алгоритмы экстраполяции параметров траекторий путем задания корректирующего шумового ускорения и замены результатов фильтрации оценок координат на измеренные значения при распознавании маневра. Обоснованы параметры фильтрации с шумовым ускорением в зависимости от точности измерений пространственных характеристик и идентификации при группировании однотипных признаков с наибольшими значениями условных вероятностей ситуаций отождествления объектов Purpose. This work addresses construction of the procedure for identifying maneuvering air objects in the process of tracking their routes. Monitoring tools during structural and system air space control are employed. The study is aimed to establish the abilities of correct identification of objects and false alarm at various standard errors of measurements of angular coordinates and to determine ways to increase efficiency of identifications performed due to selection of filtering options during trace tracking. Methodology. Identification of objects was performed according to the ideal observer criterion by comparing estimates of angular coordinates of objects subjected to linear filtering with corrective noise acceleration. In order to minimize root-mean-square errors of coordinates and motion velocity estimates of objects, route parameter extrapolation algorithms are obtained by setting correcting noise acceleration and replacing the results of filtering coordinate estimates with measured values during manoeuvre recognition. Due to a priori uncertainty of route parameters, target tracking was initially performed using recurring linear filtering while maintaining the priority of straight uniform movement. The recognition of the maneuver was carried out as a result of exceeding the difference between the measured and filtered values of the target coordinates of the threshold value. Findings. Filtering parameters with noise acceleration are justified depending on the accuracy of measurements of spatial characteristics and identification when grouping identification features with the highest values of conditional probabilities of situations for the objects under identification. As a result of replacing filtered parameters of alignments containing areas with rotations of 10 and 20, measured values for standard bearing errors (1 ... 2), the maximum error in determining directions for objects reaches 0.8 and 0.9, respectively. When replacing the estimates of the parameters of the alignments obtained using a recurring linear filter without taking into account noise acceleration, the coordinate values measured at the bearing error (0 . 5 ... 2), the errors of the filtered bearing of the targets at the angles of rotation of 10are (0 . 2 ... 1). When maneuvering objects with turns by 20, the largest value of the standard bearing error increases to 1.2. By increasing the accuracy of the diaper from 2 to 0.5, the probability of correct identification of objects in monitoring tools performing noise correction acceleration filtering increases by about 3 times and reaches a value of 0.9. As a result of replacing the estimates of the parameters of the alignments filtered taking into account the corrective noise acceleration with the results of measurements, the probability of correct identification of objects with standard bearing errors of not more than 0.5decreases from 0.9 to 0.85. Originality/value. The identification of maneuvering air objects is performed using filtering of route parameters calculated with the help of the ideal observer criterion. For the most efficient identification, the identification features belonging to the same object must be established according to the highest conditional probability of the identification situation. To minimize errors in estimation of the angular coordinates of objects, a procedure for filtering motion parameters with corrective noise acceleration is implemented

On stability with respect to the part of variables of a non-autonomous system in a cylindrical phase space

The stability problem of a system of differential equations with a right-hand side periodic with respect to the phase (angular) coordinates is considered. It is convenient to consider such systems in a cylindrical phase space which allows a more complete qualitative analysis of their solutions. The authors propose to investigate the dynamic properties of solutions of a non-autonomous system with angular coordinates by constructing its topological dynamics in such a space. The corresponding quasi-invariance property of the positive limit set of the system’s bounded solution is derived. The stability problem with respect to part of the variables is investigated basing of the vector Lyapunov function with the comparison principle and also basing on the constructed topological dynamics. Theorem like a quasi-invariance principle is proved on the basis of a vector Lyapunov function for the class of systems under consideration. Two theorems on the asymptotic stability of the zero solution with respect to part of the variables (to be more precise, non-angular coordinates) are proved. The novelty of these theorems lies in the requirement only for the stability of the comparison system, in contrast to the classical results with the condition of the corresponding asymptotic stability property. The results obtained in this paper make it possible to expand the usage of the direct Lyapunov method in solving a number of applied problems.

Symbolic Evaluation of Expressions from Racah’s Algebra

Based on the rotational symmetry of isolated quantum systems, Racah’s algebra plays a significant role in nuclear, atomic and molecular physics, and at several places elsewhere. For N-particle (quantum) systems, for example, this algebra helps carry out the integration over the angular coordinates analytically and, thus, to reduce them to systems with only N (radial) coordinates. However, the use of Racah’s algebra quickly leads to complex expressions, which are written in terms of generalized Clebsch–Gordan coefficients, Wigner n-j symbols, (tensor) spherical harmonics and/or rotation matrices. While the evaluation of these expressions is straightforward in principle, it often becomes laborious and prone to making errors in practice. We here expand Jac, the Jena Atomic Calculator, to facilitate the sum-rule evaluation of typical expressions from Racah’s algebra. A set of new and revised functions supports the simplification and subsequent use of such expressions in daily research work or as part of lengthy derivations. A few examples below show the recoupling of angular momenta and demonstrate how Jac can be readily applied to find compact expressions for further numerical studies. The present extension makes Jac a more flexible and powerful toolbox in order to deal with atomic and quantum many-particle systems.

Method and algorithm for determining the geographic coordinates of ground objects from an unmanned aerial vehicle

Introduction: As practice shows, the accuracy of determining the coordinates of objects is influenced by many factors associated with the presence of errors in measuring the angular coordinates of the optical system, the distance to the object and the presence of an inhomogeneous terrain. Purpose: Improving the accuracy of determining the geographic coordinates of ground objects from an unmanned aerial vehicle. Results: A method and an algorithm for determining geographic coordinates based on the use of a digital terrain model and optimization methods have been developed. The accuracy of calculating the coordinates of the object is increased by minimizing the error in measuring the declination angle, azimuth to the target and slant range. To confirm the analytical calculations, a field experiment was carried out with a car on the ground. At a considerable distance, at which the slant range was 900 m, several data freeze frames were taken. As a result of calculations, the geographical coordinates of the car were obtained in two ways (traditional and developed). Ultimately, the accuracy of calculating coordinates using the developed method is 4.8 times higher. Practical relevance: The method and algorithms for information processing proposed in the work will make it possible to create a number of hardware and software solutions for guidance and target designation systems.