SYSTEM ANALYSIS, CONTROL AND INFORMATION PROCESSING
Nowadays, the problem of ensuring security of systems with a critical mission has become particularly relevant. An increased opportunity for unauthorized exposure on such systems via hardware, software and communication networks is the main reason to discuss this problem. It is confirmed by a plenty of accidents when equipment is out of order by means of malicious embedded elements and viruses. Currently, in the Russian Federation the majority of control systems are based on foreign hardware and software platforms, including strategic enterprises and objects with a critical mission. Herewith, the proportion of foreign microelectronic components in such systems is more than 85 %. The article is devoted to the development of scientific basis and techniques of the assurance assessment to control systems of objects with a critical mission. It was shown, that assurance assessment to a control system is a broader index than its reliability and fault tolerance. Such index must integrate various evidences and approvals, which can be objective, based on physical and mathematical assurance assessment methods, as well as they can be subjective, based on the experts experience. A method of assurance assessment to a control system of objects with a critical mission, based on Shortliffe’s scheme, was proposed in this paper. The Shortliffe’s scheme is used in the theories of fuzzy logic for assurance assessment to a hypothesis on the basis of various evidences and statements. An important advantage of a Shortliffe’s scheme is the set of evidences, which can be broadened and augmented (for instance, on the basis of obtained experience). It allows us to clarify a certainty factor. The assessment methods of truth degree of terminal statements of various types, including those, which require the combination of objective and subjective methods of their truth degree assessment, are proposed. The proposed assurance assessment method for national development and creation standards of control systems of objects with a critical mission allows to significantly increase their functional security.
The authors analyze the technical condition of objects of railroad communications with modern bridges, tunnels, stations, overpasses, crossings and power installations. It is noted that, based on the specific features of such objects, control of their technical condition in most cases is carried out at certain intervals. At the same time, existing continuous control systems do not always adequately assess the technical condition of rail infrastructure objects due to the presence of additional noises in the processed signals at the time when a malfunction occurs. In this regard, one of the possible options is proposed for "continuous" monitoring of the beginning of changes in the technical condition of railroad tracks by means of noise technologies. It is pointed out that when the technical condition of rail infrastructure changes, vibration signals caused by the impact of rolling stock contain noises in addition to the useful component. The use of correlation and spectral analysis technologies, as well as other traditional methods does not allow ensuring the adequacy of the control results, due to the influence of the noise on useful vibration signals. Therefore, technologies are proposed for split analysis of the useful signal and the noise received from vibration, as well as for forming informative attributes of identification of the technical condition of rail infrastructure. In this case, the estimates of the characteristics of the useful signal and the noise are used as the main carrier of diagnostic information. Due to the simplicity and reliability of the developed theoretical algorithms, the implementation of the technical equipment and its installation in all objects of the railroad track present no particular difficulties. At the same time, the implementation of the Noise system will ensure real-time control of the beginning of changes in the technical condition of railroad tracks during the movement of the rolling stock. This, in turn, will allow timely detection of malfunctions, significantly enhancing the safety of passenger and cargo rail transportation.
ROBOT, MECHATRONICS AND ROBOTIC SYSTEMS
To ensure unmanned autonomous movement of ground robotic means, it is required to accurately determine the position and orientation of the robot. The present study is related to the estimation of coordinates by comparing the scans of a laser scanning rangefinder in conditions of semi-structed infrastructure and the absence of a global satellite communications signal. The existing methods of comparing scans have significant drawbacks in the conditions of movement over a semi-structured terrain, associated both with the processing time of data from the laser scanning rangefinder, and with the quality of the results obtained. The scan is preliminarily placed in a map consisting of cells. Each cell of around point scan is described by forces represented by the laws of physics or probability theory. In the cells of the map, we take into account the mutual influence of all forces from each point of the scan and thus we obtain the resulting artificial potential field of the scan. The position of the robot is estimated by the change in the number of acting forces of one scan per points of the next scan taking into account their direction. We estimate the orientation of the robot based on the sum of the vector products of the forces and distances to the given forces acting on the points of the next scan. This method allows you to calculate the displacement of the robot between scans regardless of road conditions and terrain. This article presents the results of an experimental verification of the method on a mock-up of a mobile robot equipped with a Velodyne HDL-32 LIDAR. We indicate the operating conditions of the method for a given LIDAR, as well as the time spent on calculating the bias estimate. Given the peculiarities of the LIDAR, we present a method for eliminating the Doppler Effect (distortion) for the original point cloud. A comparative analysis of the developed method for integrating wheel odometry data, inertial and satellite navigation using the Extended Kalman Filter shows the applicability of this method to assess the position and orientation of the robot in conditions of its movement over rough terrain.
Savonius rotor is one of relatively wide-spread type of wind turbines. The rotation rate of this rotor is considerably lower than that of horizontal axis wind turbines and Darrieus wind turbines. However, it starts rotating at small wind speeds, doesn’t require any additional devices to ensure its re-orientation in case of change of the wind direction, and generates a rather large torque. Therefore, it is suitable for use as a drive in different mechanical and electromechanical systems. In the present paper, dynamics of rectilinear motion of a wheeled cart is studied, which is driven by Savonius rotor installed on it. It is assumed that the wind makes a certain constant angle with the line, along which the cart moves. The aerodynamic load upon the rotor is described with an empirical model, in the context of which the aerodynamic characteristics (aerodynamic torque, drag and lateral force coefficients) are represented as Fourier series with respect to the rotor revolution angle, the coefficients of the series being functions of the rotor tip speed ratio (dimensionless angular speed). Experiments were performed in the subsonic wind tunnel of the Institute of Mechanics of Lomonosov Moscow State University intended to measure aerodynamic characteristics of the rotor at different wind speeds and rotor angular speeds. Based on experimental data, functions were proposed that approximately describe the dependence of the above mentioned coefficients upon the tip speed ratio. The obtained dependences were used for analysis of dynamics of the cart driven by the Savonius rotor. The equations of motion are averaged with respect to the angle of revolution of rotor. Steady solutions of this averaged system are studied. It is shown that, for certain values of parameters, there exist two attracting steady motions corresponding to different directions of the cart velocity. Cart dynamics in the context of the full system of equations of motion is compared with its dynamics in the context of the averaged system.
The article discusses a solution to the problem of increasing the reliability of operation of underwater robots through the use of accommodation systems that compensate for the consequences of faults that appear in the thrusters. The following types of faults were considered: 1) a fault in the rotation speed sensor of thruster, causing error in its readings; 2) overheating of the motor or short-circuiting of several turns of the winding of its armature circuit, causing a change in the value of electrical resistance; 3) the appearance of an unknown external torque effect on the engine shaft, including when winding plants on the propeller. A new method for constructing accommodation systems is proposed, which contains three stages. At the first, the detection of emerging faults is carried out using the bank of diagnostic observers. Each observer is synthesized according to a special procedure in such a way that the residual formed by it is sensitive to the appearance of various combinations of possible faults. This allows to detect each specific fault. At the second stage, the values of sensor errors and deviations of the parameters of the thruster from their nominal values are estimated by additional variable structure observers. At the third stage, additional control signals for robot’s thrusters are formed. They ensure the stabilization of dynamic properties and quality indicators of thrusters in the event of faults. The results of mathematical modeling are presented, which have confirmed the operability and high efficiency of the synthesized accommodation system.
DYNAMICS, BALLISTICS AND CONTROL OF AIRCRAFT
Problems of mathematical modeling of onboard air data systems errors are of paramount importance in pitot-static sources errors determination, air data systems evaluation in flight tests. The problems of development, identification and assessment of the mathematical models of errors adequacy acquire main importance in the modern technology of the air parameters true values determination, air data systems evaluation using satellite navigation systems, developed and applied in the practice of flight tests at JSC "FRI n.a. M. M. Gromov". This paper gives a general description of an air data systems estimation technology using satellite navigation systems. The principles of solving problems of aircraft data systems aerodynamic errors mathematical modeling are stated. The structure of mathematical models, factors of the aerodynamic errors, relationship of the solving problems of errors modeling within the framework of technology with a flight experiment plan are shown. Mathematical models parameters identification are based on a complex solving of the problems of a true air data parameters values and aerodynamic errors determination in flight tests. New results of mathematical modeling of errors in tests at high angles of attack in 2018 year of medium-range and short-range aircraft are presented. The results illustrate the technology effectiveness in solving the problems of flight tests at high angles of attack information support, aerodynamic errors modeling, air data systems estimation. The applied modeling methods make it possible to allocate in the mathematical models of pitot-static sources aerodynamic errors even the factors of very weak aerodynamic influence, comparable with the minimum pressure sensors instrumental errors.
ISSN 2619-1253 (Online)