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It is necessary to ensure appropriate information content of the measuring instruments used for intelligent diagnosing systems of energy and technological complexes based on the measurement of dynamic parameters. Sensors and measuring equipment should possess sufficient accuracy, reliability, speed and consistency of performance. Types of sensors for measuring dynamic parameters are selected depending on the systems structure. They can be, for example, sensors for the electrohydromechanical systems of these complexes, pressure sensors, as well as sensors of flow and temperature of the working media, displacement of moving elements and vibration of the base members. The type of sensor intended for use in the diagnostic system is largely determined by the dynamics of the processes taking place in it. It is necessary that the sensors satisfy their performance requirements. If the sensors have lower speed than is necessary for the process dynamics in the electrohydromechanical system, it can lead to dynamic measurement error and an error in the diagnostics of technical condition. In technical literature, the requirement for the sensor speed is indicated by the fact that it should be an order of magnitude higher than the dynamics of the processes occurring in the system. This approach is not acceptable for choosing the type of sensors for diagnostic systems, taking into account the process dynamics. Firstly, sensors for measuring with this required parameter may not be available. Secondly, even if there is a sensor with a parameter close in speed to the dynamics of the system processes, it is necessary to know in advance what dynamic error it can lead to and how it will affect the accuracy of the diagnostic system. An analytically generalized dependence of the dynamic measurement error of electrohydromechanical system parameters on the relative sensor speed is obtained in this paper. This dependence allows you to choose a sensor with a dynamic error that does not exceed a given value. The calculation of the dynamic measurement error is shown using the MI-8 helicopter hydraulic system as an example.

In order to increase efficiency of diagnostics of electro-hydro-mechanical systems (EHMS) it is advisable to have simulation models of typical faults. Such approach makes it possible to estimate in advance, even at the stage of mathematical modeling, the impact of different faults on functioning of hydraulic systems. This work is aimed at creating a database containing complexes of diagnostic features, which allow distinguishing types of faults, their causes and stages of development. In the paper, typical faults of EHMS are presented on the basis of statistical information from literature sources and experimental research. They include internal and external leakages, spool and sleeve sticking, degradation of power fluid. The causes of faults and their impact on hydraulic systems functioning are considered. Simulation models of typical faults are implemented and studied in the SimulationX software package. The static and dynamic characteristics of the systems are investigated in order to identify diagnostic signs of various faults. The impact of typical faults on various system parameters is discussed. During the research, the tasks of selecting the rational location of sensors of different types (pressure, flow, displacement, or force sensors), their quantity for recognition of a typical fault are solved. The results of theoretical and experimental studies of serviceable and faulty systems for cases of control and disturbance actions are presented. Comparative analysis of transient processes of serviceable and faulty EHMS is presented with assessment of difference between theoretical and experimental data. The results of the work allow to more rationally designing the diagnostic complex for more accurate identification of the type of fault, stage of its development and prediction of residual service life of EHMS.

For underwater robots in the past three decades, the problem of energy efficiency and acoustic noiselessness has arisen sharply. The solution of these problems is inextricably linked with the solution of the problems of dynamics and vibroacoustics arising in the flow of a liquid under the flow of underwater bodies. These problems include the problem of the pressure pulsations occurrence and velocity distributed over the surface of the object, as well as noise and vibrations caused by these pulsations. To create energy-efficient and low-noise underwater robots, it is necessary to create methods for influencing the structure of wall currents and the shape of the aerodynamic surfaces of the robot in order to reduce its surface friction, as well as impedance. In this paper, we consider the development of an experimental bench for testing the main executive systems of an underwater robot with an anisotropic hull, including a buoyancy variation system, a trim and roll change system, and a hull geometry changing system.

The development of a prototype of an underwater robot with a variable geometry of the body is a major complex task, including a whole series of tasks of a scientific, technical, engineering and applied nature, and the creation of new automatic systems for managing it. The creation of such a robot will ensure its high autonomy and maneuverability. In this paper, the development of a solid model of a biomimetic robot hybrid and AUV with a variable geometry of the hull is presented. Also presented is a basic pneumatic circuit integrated into the robot body, which drives the pneumatic muscles fixed to the ribs of the robot’s robust body. The experimental part includes the investigation of the vertical and horizontal components of the deformation of the walls of the shell, depending on the pressure supplied by the pneumatic system to the pneumatic cusps.

The gas pressure control units are widely used for various applications. Very often such units operate at large flow rates and pressure drops, thus becoming a powerful noise sources. The problem of noise reduction and protection is a formidable challenge for the design and operation of such units. One of the ways for noise reduction is a muffler installation. However, the in-line installation of such devices may cause malfunction of the pressure reducing valve. Any variation in the output line impedance may provoke instability and self-exited oscillation of the regulator. In this paper the muffler's effect on pressure reducing valve dynamics is studied. The subject of research is a muffler installed at the pressure reducing valve outlet. The mathematical model of this system is implemented in the Simulink software to analyze the muffler impact on pressure reducing valve static and dynamic characteristics and to estimate the system noise level. The dependences between the system and muffler parameters are obtained as a result of simulation. The experimental research at the pneumatic bench is implemented for mathematical model verification. The muffler effect on transient process quality is analyzed. Stability domains are calculated and the muffler influence on system stability margin is evaluated. The theoretical results demonstrate acceptable correlation with experimental data.

The main noise source in gas distribution systems is the gas pressure reduction in regulators. Nowadays the special mufflers, representing a set of orifices, are widely used for pressure regulator noise reduction. However, the installation of such devices may cause malfunction of the unit. That is why there is a need to study the characteristics of regulator with the muffler in order to select the parameters at which the desired pressure reduction is retained and the noise is reduced.This paper studies the regulator which represents an equivalent of reduction valve of a similar scheme with the muffler installed in the outlet line. The output impedance increase may lead to loss of stability and control accuracy. The mathematical model of this system was implemented in the Simulink software in order to analyze the muffler impact on pressure relief valve static and dynamic characteristics. The program in Matlab software was also developed for determination of the noise generated by the system. The experimental research using the pneumatic bench was carried out for mathematical model verification.The dependences between the main system operating parameters and the muffler flow area were obtained as a result of simulation. The muffler influence on the transient processes quality was analyzed. The areas of stability in the regulator and muffler parameter space were calculated. The muffler flow area values, providing the lowest level of the noise generated by the system were determined. The theoretical results have good correlation with experimental data.

The problem of automatic reliability monitoring and reliability-centered maintenance is increasingly important today. In this paper, we compare the accuracy of four machine learning approaches for fault detection in a hydraulic system. The first three approaches are based on SVM classifiers with linear, polynomial and RBF kernels and the last one is a gradient boosting on oblivious decision trees. We evaluate algorithms on the synthetic dataset generated by our simulation model of the helicopter hydraulic system and show that high accuracy fault detection can be achieved.

In power plant and test equipment control systems pressure sensors are often connected by pressure transmission lines for conditions of high temperatures and vibrations. In the presence of pressure pulsations in the monitored object, a restrictor is installed at the pressure transducer inlet. Restrictors serially produced for pressure transducers have a nonlinear flow-drop characteristic which leads to the additional measurement error of the medium or slowly changing component of the pulsating pressure. This distortion can significantly exceed the error of the transducer itself. The results of theoretical and experimental studies of the additional error depending on the parameters of the measurement circuit and pressure pulsations (amplitude, frequency, spectrum and phase shift between components) are presented. Recommendations on the choice of damper parameters for which the additional error can be neglected are given. The methodology developed by the authors can be used to create measurement circuit for an average or slowly changing component of the pulsating pressure measurement in power plant monitored measurement and control systems.

Providing stability and dynamic quality of fuel systems is very important problem when developing and during operation of power plants in many applications. For example, it is critical issue for longitudinal stabilization of launch vehicles (pogo attenuation). One of effective ways to provide rocket longitudinal stability is installation of a pogo suppression device (PSD) in the feed line. The paper presents a mathematical model of the gas PSD, its transient and frequency responses that can be used for the fuel system design. For developing mathematical model of the PSD, analytical methods and numerical simulation were applied, the software packages MatLab/Simulink and AMESim being used. The PSD input acoustic admittance was calculated. The developed model of the gas PSD can be used in the mathematical model of the fuel line when solving problem of longitudinal stability of launch vehicles and other issues of power plants design.