ISSN 0021-3454 (print version)
ISSN 2500-0381 (online version)
Summaries of the issue


IMPROVING ACCURACY OF FREQUENCY IDENTIFICATION BY USING A CASCADE OF ADAPTIVE FILTERS Polina Gritsenko, Aranovskiy Stanislav V., Bobtsov Alexey A., Pyrkin Anton Alexandrovich
The problem of frequency identification for a biased sinusoidal signal is considered. The use of an adaptive cascade of band-pass filters together with application of an identification algorithm is proposed to improve accuracy of frequency identification. This method may lead to significant improvement in the identification performance, to attenuation of oscillations in the signal identification error, and to reduction in the error signal bias. Numerical simulations demonstrate the proposed scheme efficiency.
ALGORITHMS FOR CONTROLLING A FLYING ROBOT WHEN THE ROBOT IS TRACKING A MOVING OBJECT Bushuev Alexander B., Grygoriy Shmyhelskiy, Bui Shon Van, Shchaev Egor G., Yury V. Litvinov
Algorithms for controlling an unmanned aerial vehicle (quadrocopter) are considered. The algorithms allow solving the problem of tracking moving objects with the use of video camera mounted on the quadrocopter. An algorithm of quadrocopter piloting along a predetermined path was developed. The algorithm applies an approximation of the original curve with small segments and it allows for simplification of the controlling by utilization of only two commands: forward movement and rotation about the vertical axis (yaw). An approach to object identification from its digital image, based on edge detection is presented. Methods of obtaining of the tracking object displacement while accounting for background inconstancy caused by the camera movements are analyzed. An algorithm for measuring distance to the tracking object using a single camera is developed. The algorithm is based on comparison of two frames taken from different altitudes, and it is a modification of the method of stereoscopic vision when the camera is hard mounted on the quadrocopter. For multiple targets in a frame, a method to measure distances to the targets is proposed. The method applicability does not depend on the targets position in the frame and therefore may be used for safe passing over obstacles along the route. Combined application of the above algorithms is reported to allow obtaining of the full set of parameters describing target position and movement, the parameters may serve as a base for creation of control commands for flying robot necessary to implement a valuable system of tracking moving objects with the use of unmanned aerial vehicles   
AGENT BEHAVIOR DEFINED BY LOGISTIC MAPPING Bushuev Alexander B., Stanislav I. Tomashevich, Alexander A. Kulchitsky, Vladimir S. Vorobev, Olga K. Mansurova
A search algorithm based on biological approach in 3D space system is considered. A search agent in the field of a spatial function serves as the tracing system. Tthe agent purpose is to determine the function extremum domain, and the agent behavior is defined by logistics mapping. the system represents search model in three-dimensional space. Modeling of the agent behavior operating in accordance with a proposed algorithm is carried out. The agent movement quality is characterized by the norm of coordinate vector of deviation of the agent from the search object.
The problem of reduction of computing expenses for digital estimation of power spectral density of a random process with correlogram method using correlation windows is considered. A solution to the problem is obtained with the use of a signanalog stochastic quantization as a primary transformation of the random process under investigation. Estimates of the correlation function calculated from the sign-function signals and discrete-time representation of these signals make is possible to carry out an analytical calculation of the integral cosine transformation of correlation window function when spectral estimation algorithm is designed. The well-known window functions by Bartlett, Hann, Hamming, Blackman, and Nuttall are considered as examples. The developed algorithm for spectral power density estimating does not require direct calculation of the correlation function estimates to be carried out preliminary. The algorithm uses logical operations and simple arithmetic operations of addition and subtraction, and therefire reduces the complexity of digital estimation of power spectral density. 
This paper presents a multiagent simulation of passenger evacuation in case of the inclination of a ship under the storm. Evacuation process depends on many different factors: environmental properties (such as wind velocity, intensity of waves), behavioral aspects of a human and so on. In order to describe a passenger's behavior in an evacuation situation considering the inclination of a ship, we use a force-based model adapted from multiagemt system. Our approach provides an opportunity to estimate evacuation time depending on intensity of waves, rate of sailing and relative direction. Proposed model can be used in couple with ship flooding or fire propagation simulation and also it can be used in decision support systems for crew assistance.  


Optical schematic of an afocal compensator of aberrations composed of two identical telescopic lenses is described. The corrective properties of the compensator are studied. A method for calculation of the schematic based on theory of the third-order aberration theory is presented. As an advantage of the schematic, it is noted that the compensator does not cut back focal length of the optical system and does not affect the system optical power. An example is presented of calculation of the afocal compensator for correction of field aberration in two-component lens.
An autonomous astronomical system for artificial satellite navigation and orientation is presented. The system makes use of “satellite–star” angle measurements with optical-electronic instruments. A reciprocal angles method and a tracking method are developed to solve the navigation problem. In both the methods, the line-of-sight direction is calculated from obtained estimates of the satellite orientation. Along with generation of high-precision navigation data on the satellite under observation, the tracking method reveals the facts of the satellite orbit change (maneuver) even under weak pulse (1—3 m/s). Results of simulation testing of the developed methods are presented. 
The suggestion that output power of a PV solar module may increase due to ambient radiation reflected by a snow covering is tested experimentally.  The current generated by the additional radiation from underlying snow surface is determined. Experiments are performed to estimate the effect of snow on the module surface on the solar cell performance.


The structural solution and speed subsystem synthesis method for 4-loop control system for angle of twin-motor servo drive of biaxial telescope elevation axle are presented. A parametric method of the system synthesis is developed for the case when the executive axle may be represented with a three-mass unbranched mathematical model. A vector-matrix mathematical model of speed subsystem suitable for the dynamic processes analysis is proposed. A comparative analysis of the transient characteristics of speed subsystems designed with the use of the described method and mathematical model is carried out for one- and two-motor servo drive of the telescope. Results of simulation demonstrate that with the two-motor speed, the frequency bandwidth determining its speed, may be twice as large as with the one-motor subsystem.  The difference is achieved due to higher resonant frequency of the two-motor mechanism, and halved the mass ratio defining the regulators parameters. The second factor is the most important, as it allows to double the speed even with close values of the three-mass mechanism resonance frequencies. 
General expressions for frequency transfer function of Butterworth complex bandpass filter are derived with the use of the residue theory. The pulse characteristic of a complex filter is shown to be a complex one, phase-shift between the real and imaginary components of the function equals 90. A method is proposed for calculating the real and imaginary components of the pulse characteristic of a complex Butterworth bandpass filter of arbitrary order. Concrete examples are presented. 


The problems of comparison and selection of engineering design solutions for a mechanical system are analyzed by the example of automatic gripper for handling components of control and protection system of a nuclear reactor (cluster of fuel assembly). Based on the method of expert evaluations proposed by the authors, analysis of the existing (used in the nuclear industry) automatic gripper functioning is carried out, peculiarities and limitations of its design are revealed. A new design for automatic gripper is proposed to provide a higher level of reliability of the system in question. A comparison of two engineering solutions for evaluation of the mechanical device quality is performed. 


Evolution of energy distribution function for photo-excited charge carriers In a semiconductor and dielectric under the action of femtosecond laser pulse is analyzed. The consideration is based on Boltzmann kinetic equation for the carriers with due regard for the effects of interzone absorption as well as intra-zone absorption and collision relaxation. Thermalisation time for photo-excited electrons is estimated. The influence of saturation of interband absorption on concentration of free electrons is studied. Dependence of concentration of photo-excited electrons on energy density in incident femtosecond laser radiation.  


This article discusses implementation of a multi-disciplinary educational environment in the field of computer simulation as a tool to create conditions and to stimulate lifelong learning, creativity and intercultural competencies of future graduates of international double degree Master's programs of ITMO University, Russia and University of Amsterdam, the Netherlands. Teaching methods are based on the diversification of global academic and professional activities of master students by their immersion in group multidisciplinary research projects. Environment’s structure consists of the model of desired competencies of our graduates, which in turn is based on a generalized life cycle of the object of development, e.g. a mathematical model and its specifics in various subject areas. Along with professional and general cultural competencies, special attention is paid to the development of technological competencies for the efficient use of computing systems of different architecture and a variety of programming technologies, as well to the formation of creativity of the graduate.