Belarusian State Aviation Academy

The problem of analytical synthesis of the control acceleration of an unmanned aerial vehicle (UAV) of a multirotor type is being solved in relation to a light quadrocopter with a high flight duration. The optimal control is analytically determined for a given minimized quality functional in the form of the minimum time required to transfer the UAV from a given initial to a given final position in space. A mathematical model of the movement of the UAV mass center in a given plane relative to the earth's surface is considered. A feature of the proposed technique is the solution of the problem of maximum speed (forced control) based on the consideration of the laws of kinematics of uniformly accelerated motion of a rigid body. For given characteristics of the maximum allowable speed and control acceleration of the UAV, the moments of switching of the control signal are analytically calculated, which can be implemented in the UAV autopilot. This allows, in contrast to classical methods for solving the problem of forced control, to get rid of the need to solve a two-point boundary value problem and consider additional transversality conditions. The computer simulation of the obtained analytical results in the form of processes of changing the control acceleration, as well as the UAV motion parameters, has shown the efficiency of the proposed technique and the prospects for its use at the initial stage of the synthesis of the UAV control system.

Abstract The authors consider main elements of the global navigation satellite system (GNSS) and peculiarities of its operation in the multi-system mode and with a pseudolite as an augmentation. A simulation modeling complex for orbital groupings of systems forming the GNSS was presented. By comparing the results of natural experiments and mathematical modeling the performance of the complex with regard to the BeiDou system was estimated. The vertical dilution of precision was estimated for all possible modes of GNSS application as well as with a pseudolite used. The technique of finding an optimal pseudolite position was proposed and efficiency of its use in all possible modes of GNSS application was estimated.KeywordsGlobal navigation satellite systemMulti-system modeAugmentationPseudoliteVertical dilution of precisionOptimization

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The study on forming the expansion of fluidized bed of conductive particles is carried out.

A new kinetic calculation approach for the complex process of the heavy tar thermal decomposition under non-isothermal conditions is proposed based on modification of Coats-Redfern method.

The article presents the results of computational and experimental studies of the distribution of a model material (plastic spherical particles with a size of 6 mm) along the height of a laboratory two-dimensional apparatus of the fluidized bed of the periodic principle of action. To experimentally determine the distribution of the solid phase over the height of the apparatus, digital photographs of the fluidized bed were taken, which were then analyzed using an algorithm that had been specially developed for this purpose. The algorithm involved splitting the image by height into separate rectangular areas, identifying the particles and counting their number in each of these areas. Numerical experiments were performed using the previously proposed one-dimensional cell model of the fluidization process, constructed on the basis of the mathematical apparatus of the theory of Markov chains with discrete space and time. The design scheme of the model assumes the spatial decomposition of the layer in height into individual elements of small finite sizes. Thus, the numerically obtained results qualitatively corresponded to the full-scale field experiment that had been set up. To ensure the quantitative reliability of the calculated forecasts, a parametric identification of the model was performed using known empirical dependencies to calculate the particle resistance coefficient and estimate the coefficient of their macrodiffusion. A comparison of the results of numerical and field experiments made us possible to identify the most productive empirical dependencies that correspond to the cellular scheme of modeling the process. The resulting physical and mathematical model has a high predictive efficiency and can be used for engineering calculations of devices with a fluidized bed, as well as for setting and solving problems of optimal control of technological processes in these devices for various target functions.

We present a moments-based approach to the performance analysis of L-branch equal-gain combining and maximal-ratio combining receivers, operating in independent or correlated, not necessarily identically distributed, Weibull fading. For both equal-gain combining and maximal-ratio combining receivers the moments of the output signal-to-noise ratio are obtained in closed-form. An accurate approximate expression is derived for the moment-generating function of the output signal-to-noise ratio of the equal-gain combining receiver utilizing the Padé approximants theory, while a closed-form expression for the corresponding MGF of the maximal-ratio combining receiver, is obtained. Significant performance criteria, such as average output signal-to-noise ratio, amount of fading and spectral efficiency at the low power regime, are extracted in closed-forms, using the moments of the output signal-to-noise ratio for both independent and correlative fading. Moreover, using the well-known moment-generating function approach, the outage and the average symbol error probability for several coherent, non-coherent, binary, and multilevel modulation schemes, are studied. The average symbol error probability of dual-branch equal-gain combining and maximal-ratio combining receivers is also obtained when correlative fading is considered in the diversity input branches. The proposed mathematical analysis is illustrated by various numerical results and validated by computer simulations.

Transmit diversity under transmission of signals from the base station to mobile station using the code-division multiple-access (CDMA) system allows us obtaining the performance gains close to the mobile station receiver diversity without complexity of the mobile station receiver antenna array. The multipath diversity can be achieved using the pre-RAKE precoding at the transmitter that could be employed and there is no need to install the RAKE receiver at the mobile station. We investigate several transmitter diversity techniques employed by wideband CDMA (W-CDMA) systems. We also study a possibility to combine transmitter diversity and precoding that achieves the gain of maximum ratio combining of all space and frequency diversity branches jointly with long-term prediction algorithm. It was demonstrated that the performance of the space-time pre-RAKE method approaches the performance of the maximum ratio combining for all space and frequency diversity branches. It is shown that all closed loop methods depend on the long range prediction to approximate the ideal performance in the fast fading environment.

The article discusses a mathematical model of wind, taking into account its stochastic component and wind of a steady direction, presents the results of a comparative analysis of the effect of wind parameters on the total wind velocity vector acting on unmanned aerial vehicles (UAV). The main non-line arities of the autopilot servo elements and their influence on the output signal are considered. The reaction of the contour of the UAV flight altitude stabilization to the wind is considered, taking into account the nonlinearity of the servo drive elements. Proved the need to take into account the wind in the synthesis of automatic control systems (ACS) and the contours of the angular stabilization of the drone at stages where the flight speed of the drone is less than 30 m / s.