No 3 (2024)

The problem of stabilizing a chain of two integrators by a feedback in the form of nested sigmoids is considered. Such a feedback allows one to easily take into account boundedness of the control resource and ensure the fulfillment of desired characteristics of the transient process, such as a given exponential rate of the deviation decrease near the equilibrium state and the constraint on the maximum velocity. Global stability of the closed-loop system is proved by constructing its Lyapunov function.

We consider a linear controllable third-order mechanical system whose matrix has one positive eigenvalue. The system can serve as a mathematical model of a linearized inverse pendulum controlled by an active dynamic damper. A modulus constraint is imposed on the value of the control variable. Using Pontryagin’s maximum principle, the problem of synthesizing an optimal control that brings the system to a state of rest in a minimum time is solved.

We propose an effective analytic method for solving the problem of modal control by output for a wide class of linear stationary systems in which the sum of inputs and outputs can be not only greater than or equal to, but also less than the dimension of state vector. The method is based on bringing modal control by output to modal observation with fewer inputs. At the same time, it is not necessary to additionally ensure the solvability of the connecting equation between the matrix of observer and the desired matrix of controller by output. The reduction is performed by constructing a generalized dual canonical form of control using the operations of block transposing and rank decomposition of matrices. The method significantly expands the class of systems for which an analytic solution exists, compared to the previously proposed approaches, since it is not rigidly tied to the control system dimension and also does not require mandatory zeroing of the column and obtaining a system with a single input. Based on the proposed method, a strict algorithm for analytic solution of problems from the considering class is formed. A simple and convenient necessary condition for the reducibility of modal control by output to modal observation with fewer inputs is also obtained, which allows evaluating the possibility of its analytic solution only by the form of original task. Examples of various order tasks of modal control by output in which the sum of inputs and outputs is less than or equal to the dimension of state vector are considered in symbolic form. A detailed analytic solution of the proposed examples demonstrates the effectiveness of the proposed approach practical application.

In this paper, an approach is proposed to identify the thrust force of engines and the aerodynamic drag force of aircraft according to flight test data. To obtain separate estimates of thrust and drag forces, measurements of longitudinal and normal load factors, angle of attack, true airspeed and barometric altitude are used. The advantage of the proposed approach is that it does not require the use of gas-dynamic models of the engine, flying laboratories, force measurements in the engine mounting points, or the installation of additional sensors in the engine. Despite these advantages, in practice, such an approach is usually not used, since it leads to a poorly conditioned or incorrect identification problem due to the high degree of linear relationship between the vectors of thrust and drag forces. This article suggests ways to solve the problem of poor conditionality, consisting of the development of a special test maneuver that improves the degree of conditionality of the problem, as well as the use of the special smoothing of random measurement errors using the equations of motion of the aircraft.

An oscillator with quadratic-law damping subjected to two successive instantaneous impacts is considered; the impacts have the same directions and their total impulse is given. The worst-case disturbance that maximizes the peak absolute value of the displacement of the oscillator’s body from the equilibrium position (taken as a performance index) is sought. The parameters of the two-impact disturbance that provides a maximum for the performance index are determined. A comparison of the worst-case two-impact disturbance with the worst-case rectangular pulse disturbance in terms of the value of the performance index is performed; both disturbances have the same impulse. It is shown that the worst-case rectangular pulse provides a larger value for the peak absolute value of the displacement of the oscillator than the two-impact disturbance does.

The longitudinal vibrations of an elastic rod controlled by normal forces in the cross section, which are uniformly distributed along the length over a selected interval, are studied. Such a system can be implemented using an actuator consisting of piezoelectric elements located along the axis of the rod. Criteria for the uncontrollability of individual vibration modes are given. A generalized solution to the initial-boundary value problem is found applying d’Alembert traveling waves, which are determined on the space-time mesh formed by characteristics. Linear combinations of the traveling wave and control functions define the sought displacements and dynamic potential in the energy space. The latter in a certain way relates the momentum density and the force in the cross section. The problem is to transfer the rod to a prescribed state in a fixed time while minimizing the norm of the control force. The optimal motion and the corresponding feedforward control law are found by reducing the original problem to a one-dimensional variational one. The example shows the control of vibrations for certain geometric parameters of the piezoelectric actuator.

Within the framework of computational experiments, burst and limiting modes of multiuser network control are analysed when flows are transmitted along the shortest routes. A method of approximating the set of admissible inter-node flows and a procedure for obtaining multi-parametric estimates of the system performance are proposed. In the limiting mode, all edges of the network are fully loaded and the maximum possible total inter-node flow is achieved. In the burst mode, the distribution of flows from each node is carried out without taking into account the other correspondents. The found values allow us to determine the allowable loads and specific costs of flow transmission. On the basis of the calculated outgoing node multiflows, an approximation of the set of allowable inter-node flows is constructed. Different ways of graphical representation of experimental results and display of metric estimates are given. Networks with different structural features and the same total capacity are investigated.

The article discusses the problems associated with the study of the occurrence of systematic errors in visual perception, manifested in the form of illusions. The level of existing technology demonstrates a lack of technical means and methods aimed at studying visual perception in conditions of the occurrence of visual illusions. In this regard, the authors proposed a testing methodology and an automated system that allows us to systematize the process of studying visual illusions. Based on the proposed model, a study of the visual illusion of intersection was carried out (Poggendorff illusion), which occurs when the visual perception of a diagonal line partially passing behind an opaque object. The dependence of systematic errors that arise when determining the location of the output segment, relative to the input, on the geometric parameters and configurations of figures causing the illusion was studied.

The paper proposes a technology for extraction of vascular tissue of the human eye and calculation of chorioidal vascular index on optical coherence tomography images. The applied approach is based on the use of the method of shadow compensation of optical coherence tomography (OCT) images with their subsequent filtering and binarisation. The technology made it possible to automate the calculation of chorioidal vascular index value, which is an important indicator in the study of the vascular layer when diagnosing eye diseases.

GLONASS characteristics improving task in the context of modern competitive development of global satellite navigation systems is considered. The authors consider research and development related, firstly, to improving the signal-in-space ratio indicator in an operational mode by creating new technological cycles on board the spacecraft and involving on-board hardware in these processes, and, secondly, with the formation of a reserve to orbital groupings functionality subsequent implementation without downloading ephemeris-temporal information and time-frequency corrections from the ground control complex. The article considers the main factors hindering the implementation of the currently set goals, and also suggests ways to eliminate or level the influence of these factors by developing and implementing special information technologies using modern and promising on-board hardware placed on board the GLONASS spacecraft and its potential additions.

The problem of providing an emergency landing of an unmanned aerial vehicle (UAV) helicopter type flying in a certain area of the target application is considered. The two-stage algorithm for finding an unprepared landing pad taking into account a set of requirements is proposed. At the first stage, using a digital elevation map placed on an UAV helicopter type board a route for overflying unprepared landing pads in terms of surface topography is calculated. A route formation is achieved by sequentially solving static optimization problems in order to minimize the average losses that occur when an UAV helicopter type flying from one an unprepared landing pad to another. At the second stage, which is implemented directly during an UAV’s helicopter type movement along the calculated route, the final choose of an unprepared landing pad is made based on the processing of ground penetrating radar data. A neural network classifier based on a two-layer perceptron is used to assess the suitability of an unprepared landing pad to the soil density requirement. An example that illustrates the operation of the proposed algorithm both under the conditions of a computational experiment and during a series of flight experiments is considered.