scholarly journals STUDY OF SYSTEMS WITH ELECTRODYNAMIC AND ELASTIC CONNECTIONS UNDER HARMONIC EXCITATION

2021 ◽  
Author(s):  
E. Kalinin ◽  
◽  
A. Korobko A.
Keyword(s):  
Exact Analytical Solution ◽  
Dynamic Properties ◽  
Nonlinear Differential Equations ◽  
Computer Time ◽  
Harmonic Excitation ◽  
Analytical Models ◽  
Combined System ◽  
Subsequent Formation ◽  
Resonance Modes ◽  
Electronic Model

Abstract Purpose of the study is to analyze the operation of a mechanical system with the introduction of electrodynamic and elastic components into it to ensure that the operating modes of the latter go beyond the resonance modes. The tasks of the research involve the synthesis of the mathematical apparatus with the subsequent formation and analysis of the amplitude-frequency characteristics of the specified system. Research methods. The methodological basis of the work is the generalization and analysis of the known scientific results of the dynamics of systems in resonance modes and the use of a systematic approach. The analytical method and comparative analysis were used to form a scientific problem, form a goal and formulate research objectives. When creating empirical models, the main provisions of the dynamics of systems were used. The results of the study. Considering that the dynamic properties of the system depend on the presence or absence of an elastic connection of the transmission line, a combined system was subjected to research. Since it is impossible to obtain an exact analytical solution of the obtained system of nonlinear differential equations, the solution was carried out on an electronic model with harmonic excitation. Based on the results of studies on an electronic model, using the MatLab computer modeling system, it is difficult to establish the influence of the ratio of various parameters, with their possible variations in a large range, on the behavior of the system itself, since a question posed in this way will require a significant amount of computer time. Therefore, a study of the system with harmonious excitation in its linearized form was carried out. Conclusions. A mathematical model of the functioning of a system with electrodynamic and elastic coupling under harmonious excitation has been formed. On the basis of the research carried out, the amplitude-frequency characteristic of the system was built, with the help of which the correspondence of the results of the solution of the electronic (reference), built on the basis of MatLab, and the analytical models was established.

scholarly journals On the Effects of Structural Coupling on Piezoelectric Energy Harvesting Systems Subject to Random Base Excitation

Aerospace ◽  
2020 ◽  
Vol 7 (7) ◽  
pp. 93
Author(s):  
Hamidreza Masoumi ◽  
Hamid Moeenfard ◽  
Hamed Haddad Khodaparast ◽  
Michael I. Friswell
Keyword(s):  
Energy Harvesting ◽  
Mechanical Response ◽  
Harmonic Excitation ◽  
Point Of View ◽  
Analytical Models ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
Novel Approach ◽  
Band Limited ◽  
Multi Body

The current research investigates the novel approach of coupling separate energy harvesters in order to scavenge more power from a stochastic point of view. To this end, a multi-body system composed of two cantilever harvesters with two identical piezoelectric patches is considered. The beams are interconnected through a linear spring. Assuming a stochastic band limited white noise excitation of the base, the statistical properties of the mechanical response and those of the generated voltages are derived in closed form. Moreover, analytical models are derived for the expected value of the total harvested energy. In order to maximize the expected generated power, an optimization is performed to determine the optimum physical and geometrical characteristics of the system. It is observed that by properly tuning the harvester parameters, the energy harvesting performance of the structure is remarkably improved. Furthermore, using an optimized energy harvester model, this study shows that the coupling of the beams negatively affects the scavenged power, contrary to the effect previously demonstrated for harvesters under harmonic excitation. The qualitative and quantitative knowledge resulting from this analysis can be effectively employed for the realistic design and modelling of coupled multi-body structures under stochastic excitations.

A Study of Linear Joint and Tool Models in Spindle-Holder-Tool Receptance Coupling

2005 ◽  
Author(s):  
Timothy J. Burns ◽  
Tony L. Schmitz
Keyword(s):  
Frequency Response ◽  
High Speed ◽  
Nonlinear Least Squares ◽  
Analytical Models ◽  
Connection Matrix ◽  
Depth Of Cut ◽  
Combined System ◽  
Receptance Coupling ◽  
Overhang Length ◽  
Exponential Trend

The dynamics of a spindle-holder-tool (SHT) system during high-speed machining is sensitive to changes in tool overhang length. A well-known method for predicting the limiting depth of cut for avoidance of tool chatter requires a good estimate of the tool-point frequency response (FRF) of the combined system, which depends upon the tool length. In earlier work, a combined analytical and experimental method has been discussed, that uses receptance coupling substructure analysis (RCSA) for the rapid prediction of the combined spindle-holder-tool FRF. The basic idea of the method is to combine the measured direct displacement vs. force receptance (i.e., frequency response) at the free end of the spindle-holder (SH) system with calculated expressions for the tool receptances based on analytical models. The tool was modeled as an Euler-Bernoulli (EB) beam, the other three spindle-holder receptances were set equal to zero, and the model for the connection with the tool led to a diagonal matrix. The main conclusion of the earlier work was that there was an exponential trend in the dominant connection parameter, which enabled interpolation between tip receptance data for the longest and shortest tools in the combined SHT system. Thus, a considerable savings in time and effort could be realized for the particular SHT system. A question left open in the earlier work was: how general is this observed exponential trend? Here, to explore this question further, an analytical EB model is used for the SH system, so that all four of its end receptances are available, and the tool is again modeled as a free-free EB beam that is connected to the SH by a specified connection matrix, that includes nonzero off-diagonal terms. This serves as the “exact” solution. The approximate solution is once again formed by setting all but one SH receptance equal to zero, and the connection parameters are determined using nonlinear least squares software. Both diagonal and full connection matrices are investigated. The main result is that, for this system, in the case of a diagonal connecting matrix, there is no apparent trend in the dominant connecting spring stiffness with tool overhang length. However, in the full connecting matrix case, a general constant trend is observed, with some interesting exceptions.

Dynamics of Deformable Fractal Surface in Contact with Harmonically Excited Rigid Flat

2017 ◽  
Vol 7 (2) ◽  
pp. 38-62
Author(s):  
Tamonash Jana ◽  
Anirban Mitra ◽  
Prasanta Sahoo
Keyword(s):  
Rough Surface ◽  
Dynamic Properties ◽  
Element Model ◽  
Harmonic Excitation ◽  
System Response ◽  
Fractal Surface ◽  
Fractal Rough Surface ◽  
Mass Damper ◽  
Relationship Of ◽  
Force Displacement

Dynamics of contact between a deformable fractal rough surface and a rigid flat is studied under harmonic excitation to the flat surface. Fractal surface is generated from the modified Weierstrass-Mandelbrot function and is imported to ANSYS to construct the finite element model of the same. A parameter called ‘nonlinearity exponent', is obtained from the force-displacement relationship of the rough surface and is used to find out the dynamic properties of the contacting interface using single spring-mass-damper model. The effect of variation in surface roughness and material properties on the system response is analyzed. The system exhibits superharmonic responses for different values of the nonlinearity exponent. The phase plot and time-displacement plots for the system are also furnished.

scholarly journals Determination of Period of RC Buildings by the Ambient Vibration Method

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Mehmet Inel ◽  
Hayri Baytan Ozmen ◽  
Bayram Tanik Cayci
Keyword(s):  
Natural Vibration ◽  
Dynamic Properties ◽  
Shear Walls ◽  
Vibration Signal ◽  
Analytical Models ◽  
Ambient Vibration ◽  
Seismic Behaviour ◽  
Infill Wall ◽  
Infill Walls ◽  
Vibration Period

Determining the dynamic properties of structures is important for understanding their seismic behaviour. Ambient vibration signal measurement is one of the approaches used to determine the period of structures. Advantages of this method include the possibility of taking real-time records and presenting nondestructive and rapid solutions. In this study, natural vibration periods are calculated by taking ambient vibration signal records from 40 buildings. The height of the building, infill wall effect, presence of seismic retrofit, and presence of damage are taken into consideration, and their effects on natural vibration periods are investigated. Moreover, the results are compared with the analytical methods to reveal the differences. A significant correlation between the period and height of the building is observed. It is seen that the natural vibration periods of the buildings decrease by 7% to 30% (15% on average) due to infill wall contribution. However, the efficiency of infill walls decreases as the building height increases. Another significant result is that adding shear walls substantially decreases the vibration period values by 23% to 33% with respect to the shear wall ratio. When the analytical estimates and measured building period results are compared, it is seen that analytical models have closer period estimates before infill walls are implemented. The limited data in scope of the study suggest that significant differences may present in the analytical and measured periods of the buildings due to infill wall contributions.

scholarly journals Balancing Energy Processes in Turbine Engines

2015 ◽  
Vol 21 (4) ◽  
pp. 48-56
Author(s):  
Włodzimierz Balicki ◽  
Paweł Głowacki ◽  
Stefan Szczeciński ◽  
Zbigniew Korczewski ◽  
Adam Kozakiewicz ◽  
...  
Keyword(s):  
Physical Model ◽  
Dynamic Properties ◽  
Turbine Engines ◽  
Combined System ◽  
Long Distance ◽  
Turbofan Engines ◽  
Marine Propulsion ◽  
Balancing Energy ◽  
Marine Applications ◽  
Energy Processes

Abstract The article discusses the issue of balancing energy processes in turbine engines in operation in aeronautic and marine propulsion systems with the aim to analyse and evaluate basic operating parameters. The first part presents the problem of enormous amounts of energy needed for driving fans and compressors of the largest contemporary turbofan engines commonly used in long-distance aviation. The amounts of the transmitted power and the effect of flow parameters and constructional properties of the engines on their performance and real efficiency are evaluated. The second part of the article, devoted to marine applications of turbine engines, presents the energy balance of the kinetic system of torque transmission from main engine turbines to screw propellers in the combined system of COGAG type. The physical model of energy conversion processes executed in this system is presented, along with the physical model of gasodynamic processes taking place in a separate driving turbine of a reversing engine. These models have made the basis for formulating balance equations, which then were used for analysing static and dynamic properties of the analysed type of propulsion, in particular in the aspect of mechanical loss evaluation in its kinematic system.

scholarly journals Parallel Numerical Simulation of the Magnetic Moment Reversal within the φ0-Josephson Junction Spintronic Model

2020 ◽  
Vol 226 ◽  
pp. 02018
Author(s):  
Stefani Panayotova ◽  
Maxim Bashashin ◽  
Elena Zemlyanaya ◽  
Pavlina Atanasova ◽  
Yury Shukrinov ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Magnetic Moment ◽  
Information Technologies ◽  
Parallel Implementation ◽  
Numerical Study ◽  
Nonlinear Differential Equations ◽  
Computer Code ◽  
Computer Time ◽  
Physical Parameters ◽  
Wide Range

The φ0-Josephson Dushanbe, Tajikistanjunction model with a coupling between the magnetic moment and the Josephson current in the “superconductor–ferromagnet–superconductor” system has been investigated. Numerical solution of the respective system of nonlinear differential equations is based on the two-stage Gauss–Legendre algorithm. For numerical simulation in a wide range of parameters which requires a significant computer time, a parallel MPI=C++ computer code has been developed. Results of numerical study of the magnetization effect depending on physical parameters, as well as results of methodological calculations demonstrating the efficiency of the parallel implementation, are presented. Calculations have been carried out at the Heterogeneous Platform “HybriLIT” and on the supercomputer “Govorun” of the Multifunctional Information and Computing Complex of the Laboratory of Information Technologies, JINR (Dubna).

scholarly journals Series Loss-Free Resistor: Analysis, Realization and Applications

2020 ◽  
Author(s):  
Ivo Barbi
Keyword(s):  
Power Systems ◽  
Output Voltage ◽  
Exact Analytical Solution ◽  
Nonlinear Differential Equations ◽  
Transient Behavior ◽  
Free Charge ◽  
Dc Microgrids ◽  
Input And Output ◽  
Voltage Clamping ◽  
Conduction Mode

<b>An analysis of the transient behavior of DC networks consisting of voltage sources, capacitors, and series loss-free resistors (SLFRs) is presented. The realization of an SLFR was achieved by means of a topological variation of the positive output-voltage buck-boost converter operated in discontinuous-conduction mode (DCM). It is demonstrated that even simple RC circuits containing SLFRs exhibit behavior that is described by Abel nonlinear differential equations, which do not have an exact analytical solution. Some possible applications of the SLFRs in power electronics, DC microgrids and renewable energy power systems, include loss-free charge and discharge of capacitor banks, voltage equalization of capacitors, and loss-free voltage clamping circuits. The concept of the SLFR can also be applied for voltage control in DC microgrids, employing the droop voltage technique, equalization of power and current in voltage sources associated in parallel (including batteries and DC-DC converters), and also input and output voltage natural balance in input-series output-series (ISOS) association of DC converters. The theoretical analysis results are validated via numerical examples and computer simulation.</b>

scholarly journals STABILITY OF VIBRATIONS OF THE TRACTOR AS A TWO-MASS MODEL WITH TWO NONLINEARITIES OF THE TYPE OF DRY FRICTION IN RESONANCE MODES

2021 ◽  
Author(s):  
E. Kalinin ◽  
◽  
Y. Kolesnik ◽  
M. Myasushka
Keyword(s):  
Differential Equations ◽  
Dry Friction ◽  
System Analysis ◽  
Nonlinear Differential Equations ◽  
Support Surface ◽  
Systems Methodology ◽  
Friction Forces ◽  
Resonance Modes ◽  
At Resonance ◽  
Relative Friction

Purpose of the study is to assess the possibility of calculating the stability of tractor oscillations as a system with nonlinearities such as dry friction due to the inverse problem. Research methods. The methodological basis of the work is the generalization and analysis of known scientific results regarding the dynamics of two-mass systems in resonance modes and the use of a systematic approach. The analytical method and comparative analysis were used to form a scientific problem, determine the goal and formulate the research objectives. When creating empirical models, the main provisions of the theory of stability of systems, methodology of system analysis and research of operations were used. The results of the study. Oscillations of the system with harmonic excitation by its base are considered (for example, the movement of a tractor on an uneven supporting surface). Oscillations of this system are described by nonlinear differential equations. To solve this equation, instead of friction dampers with friction forces, linear dampers with corresponding drag coefficients are included in the system. By solving the obtained system of linear inhomogeneous differential equations for the steady-state mode of oscillation, the amplitudes of oscillations of masses and deformation of springs with certain stiffness are determined. To clarify the effect of friction forces on mass oscillations in resonance modes, the obtained expressions were analyzed. A diagram of stability of mass oscillations in resonance modes is obtained. Conclusions. It has been established that if the coefficients of relative friction have such values that the point that is determined by them lies within the region bounded by segments 1-2 and 2-3 and coordinate axes, then during oscillations in the low-frequency resonance mode, the friction forces do not limit the increase in amplitudes fluctuations of masses, but only reduce the rate of their growth. If the point, which is determined by the coefficients of relative friction, lies in the region 1-1'-2'-3 '3-2-1, then the springs have intermittent deformation, that is, during the period of oscillation, one mass of the system has stops relative to another mass, or the last has stops relative to the support surface, or both masses move part of the period as a whole with the support surface. At resonance with a high frequency, the friction forces limit the amplitudes of mass oscillations if the coefficients of relative friction have such values that the point that is determined by them does not lie in the region bounded by segments 4-5 and 5-6 and the coordinate axes. Sections 4-5 and 5-6 define the boundaries of vibration stability at resonance (lines of critical ratios of the coefficients of relative friction).

Two-Loop System with Reference Model for Control of Spatial Movement of Cargo Underwater Vehicle

2021 ◽  
Vol 22 (3) ◽  
pp. 134-144
Author(s):  
V. F. Filaretov ◽  
D. A. Yukhimets
Keyword(s):  
Control System ◽  
Control Systems ◽  
Dynamic Models ◽  
High Efficiency ◽  
Reference Model ◽  
Dynamic Properties ◽  
Autonomous Underwater Vehicles ◽  
Nonlinear Controller ◽  
Combined System ◽  
Spatial Trajectories

Currently, autonomous underwater vehicles (AUV) are increasingly used to perform tasks related to the maintenance of underwater communications and various underwater production complexes, as well as performing underwater technological operations. To effectively perform these operations, AUV must have high-quality control systems that will ensure their accurate movement both along long spatial trajectories formed during their movement to the objects of work, and when performing complex maneuvers near underwater infrastructure objects. At the same time, the main difficulty that arises in the process of synthesis of AUV control systems is the significant non-linearity of the dynamic models of these control objects, the presence of interactions between their degrees of freedom, as well as the uncertainty and variability of their parameters. In this paper, we propose a method for synthesizing the spatial motion control system of the AUV, which allows us to take into account these negative effects. This system contains two loops. The first loop includes a combined system containing a nonlinear controller to achieve the desired dynamic characteristics of the AUV, when its parameters are equal to the nominal values, and a controller with self-tuning according to the reference model, which provides compensation for an unknown or variable part of the parameters. In this case, the parameters of the controller with the reference model are selected to reduce the possible amplitude of the discontinuous signal for controlling the AUV velocity. The second loop is a non-linear position controller that allows to take into account the dynamic properties of the velocity control loop and the kinematic properties of the AUV. The advantage of the proposed control system in comparison with traditional ones based on PID controllers is a higher control accuracy when moving along complex spatial trajectories, regardless of changes in the AUV parameters. The simulation results confirmed the high efficiency of the synthesized two-loop control system.

Vibration Measurement Techniques on an Industrial Gas Turbine Rotor Train

1998 ◽  
Author(s):  
Stefan S. Florjancic ◽  
Wes Franklin ◽  
Noel Lively
Keyword(s):  
Gas Turbine ◽  
Support System ◽  
Data Reduction ◽  
Dynamic Properties ◽  
Measurement Techniques ◽  
Turbine Rotor ◽  
Vibration Measurement ◽  
Analytical Models ◽  
System Parameters ◽  
Industrial Gas Turbine

The rotordynamic behavior of an industrial gas turbine rotor train was assessed on site, and the sensitivity to unbalance was quantified. An outline of the measurement procedure is given. Differential data reduction with test unbalances was undertaken to minimize the influence of measurement uncertainty. A test unbalance was installed for one run and then shifted by 180° for the consecutive run. With differential data, the effective dynamic properties of the rotor - support - system can be estimated more accurately. A rotordynamic model was used to identify the support system parameters based on measured data. For the analysis, the anisotropic, elliptical vibration orbits were decomposed into two counter-rotating circular orbits, and the support system parameters identified match the originally predicted values well. The methods of differential data reduction, rotor train mode shape presentation, elliptical orbit decomposition, and the link of measurement to analytical models with parameter definition are described. Examples from on-site measurements are included for illustration.

Sign in / Sign up

Export Citation Format

Share Document