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On the Effect of Current Stabilizer on Dynamics of a Small Hybrid Wind Power Generator

The use of small wind power generators remains quite relevant. In particular, they can be efficient for charging batteries in remote locations where there is no centralized power supply (including in the Arctic, Far East, etc.). They can also be used as part of missions to planets with atmospheres. One of the promising design solutions for a small wind power generator with a vertical axis of rotation is a hybrid device. It consists of two wind turbines that have a common axis of rotation: external (Darrieus wind turbine) and internal (Savonius rotor). This scheme represents a compromise between the relatively high power coefficient of the Darrieus turbine and the good startup characteristics the Savonius rotor. It is known that one of the typical battery charging modes is constant current charging. Here we consider a hybrid installation, the generator of which is connected to a current stabilizer. The load is simulated with an active resistance. It is assumed that the generator is a DC generator. A closed mathematical model of the studied system is constructed. The aerodynamic load is described using the quasi-steady approach. It is assumed that the characteristic time of electrical processes is much smaller than the characteristic time of mechanical processes. The influence of load resistance on the behavior of the system is investigated. It is shown that, under certain conditions, several steady modes (up to five) exist in the system. In this case, at least two of them are attracting. Therefore, the hysteresis of the angular speed of the steady mode is possible when the load resistance changes. It should be noted that in a number of situations, an unstable steady mode (which corresponds to a lower angular speed of the turbine than a stable one) may be preferable (for example, to reduce the load on bearings). In this regard, a resistance control strategy has been proposed to ensure stabilization of the unstable stationary regime.

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Method of Motion Path Planning Based on a Deep Neural Network with Vector Input

The article deals with the problem of path planning in a two-dimensional environment based on deep learning neural networks. Deep neural networks require large amounts of data and place high computational requirements on computing tools. The lack of sufficient data leads to a decrease in the accuracy of the neural network, and high computational requirements at the learning stage limit the use of this technology in engineering practice. In this paper, the forms of representation of the environment for the input of a neural network are studied. Vector form allows to reduce the amount of information supplied to the input of a neural network, but it leads to the need to use more complex neural networks. In this article, a combined form of representation is proposed, including a vector global and local map layout. The vector part of the map includes the position of the robot, the position of the target point and a description of obstacles. The local raster map describes the area closest to the robot. Using numerical research, the effectiveness of this form of data representation for a precise neural network is shown, compared with the raster representation of the map. In this article, two structures of neural networks are studied, one of which uses 8 possible directions of movement, and the other uses 3 possible directions of movement. It is shown that when using 3 possible directions, the cycling of trajectories planned by the neural network is eliminated, which leads to an increase in accuracy.

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Comparative Analysis of Quasi-Linear Kalman-Type Algorithms in Estimating a Markov Sequence with Nonlinearities in the System and Measurement Equations

The so-called Kalman type algorithms (KTA) are considered, among them quasi-linear KTAs introduced as a separate class, the features of which are the Gaussian approximation of the a posteriori probability density function (p.d.f.) at each step and the procedure for processing the current measurement based on the ideology of a linear optimal algorithm. The unified structure of such algorithms and their features are discussed. Two groups are distinguished the quasi-linear KTA: the first is algorithms using Taylor series expansion of the nonlinear functions, and the second is the so-called linear regression KTA. The methods of their designing are considered, and the common features are described. Detailed attention is paid to the following KTAs: the extended Kalman filter (EKF), polynomial filters of the second and third order (PF2 and PF3), as representatives of the first group, and the Unscented and Cubature Kalman filters (UKF and CKF), as representatives the second one. Their comparative analysis is carried out using the estimation problem of a scalar Markov sequence in the presence of nonlinearities in the shaping filter and in the measurement equations. For all the studied algorithms, the formulas are given in a form convenient for comparison. Based on these formulas, possible causes of a decrease in accuracy and a violation of the consistency properties are identified. Using the previously proposed procedure based on the method of statistical tests, predictive simulation was carried out, which made it possible to confirm the conclusions obtained previously on the basis of an analysis of the formulas for the algorithms being compared. The simulation also allowed to compare the computational complexity of the compared algorithms. The results of the study may be useful to developers involved in the processing of measurement information when choosing a filtering algorithm for solving specific practical estimation problems.

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On the Optimal Distribution of Traction Forces in Cable Propulsors of Mobile Robots

The analysis of methods of distribution of traction forces in various propellers of mobile robotic complexes and transport vehicles is carried out. The problem of synthesizing a method for controlling the distribution of the total traction load between interconnected electric drives of mobile robot propellers, discretely interacting with the support surface, is considered. An underwater mobile robot is simulated with several "walking-like" anchor-cable propellers, which ensure the movement of the underwater mobile robot by pulling the body to the supports located on the bottom. A mathematical model of the rectilinear motion of a mobile robotic device with walking-type propellers has been compiled. A mathematical description of the electric drive of the propulsion of such a mobile robot is proposed, taking into account its kinetic transfer function. It is shown that the total traction effort realized by a mobile robot is the source of the moment of resistance in the electric drive of each mover. In this regard, coefficients characterizing the distribution of traction force have been introduced into the differential equation of electric drives. A feature of the functions of these coefficients is their dependence on the distance traveled, speed and strength of resistance to movement. To optimize the distribution of the total power load between the thrusters, a target functional has been compiled. It is shown that as such a target functional, a requirement for a minimum of total heat losses in an interconnected electric drive of propellers can be formulated. To find the minimum of the accepted functional, the Euler-Poisson equations are compiled. As an additional limitation, the condition of physical feasibility is introduced. The results of solving such an optimization problem are presented on the simplest calculation scheme of two DC electric drives, between which the load is distributed along the rectilinear movement of a solid. As a result of solving the formulated optimization problem, the dependences of control actions for electric drives (voltage for DC electric drives), graphs of changes in the target function providing optimal distribution of traction forces between them are obtained, and the optimality of such distribution is proven.

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Control of Nonlinear Systems with Input Delay

An algorithm for control of nonlinear systems with sector nonlinearity and a constant known time-delay in the control channel is proposed. To design the control law, a predictor of the controlled variable by the time-delay value is used. Unlike the predictor of O. Smith, the predictor under consideration can be applied to unstable systems, and differently from the predictor of A. Manitius and A. Olbrot, the proposed predictor does not contain an integral component, which requires accurate implementation to predict the regulated signal. Next, based on the proposed predictors, subpredictors are built, which are a sequential connection of a series of similar predictors, but with a shorter time-delay. As a result, the use of a subpredictor allows one to control plants with a larger time-delay, which is reflected in the closed-loop system, where the time-delay is as many times less than the original one as the number of predictors used in the prediction scheme of the controlled variable. Using the method of Lyapunov-Krasovsky functionals and the S-procedure, sufficient conditions for the stability of the closed-loop system are obtained in the form of solvability of linear matrix inequalities. The asymptotic convergence to zero of the state vector and the uniformly boundedness of all signals in the closed-loop system are proven. It is shown that the resulting linear matrix inequalities depend on the parameters of the plant, sector boundaries for nonlinearity and time-delay, which makes it possible to calculate their upper values when the closed-loop system remains stable. These problems may be relevant when calculating the upper value of the sector of the nonlinearity under consideration or the upper value of the time-delay during remote control. The results of computer modeling are presented, which illustrate the efficiency of the proposed approaches and demonstrate an increase in the possible time-delay in the system when using a subpredictor scheme. The example shows that when using a serial connection of two subpredictors instead of one, the maximum time-delay in the control channel can be doubled. Moreover, in contrast to the predictor of A. Manitius and A. Olbrot, the subpredictor scheme is simple due to the lack of implementation of the integral component.

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