Computational Techniques for Simulation of Monolithic and Heterogeneous Structural Dynamic Systems

Recurrent neural networks for complicated seismic dynamic response prediction of a slope system

A modal projection-based reduction method for transient dynamic responses of viscoelastic systems with multiple damping models

Chapter 12 - Pseudo-Dynamic Tests and Analysis on Semi-Rigidly Jointed Steel Frames

: Measurements in dynamical systems provide the important data which is used to assess the accuracy of theoretical models and their improvement if necessary, provide monitoring information for damage detection including system aging, etc. Acquiring data from structural systems has traditionally been accomplished using strain gages or conventional accelerometers. However, with the rapidly improving processing capabilities of digital systems, (non-contacting) optically-based transducers are becoming an increasingly popular means of extracting data from experimental systems. The funded grant was used to acquire a state-of-the-art Laser Doppler Vibrometer system to measure the dynamic response of structural and aeroelastic systems of interest to the Air Force. The research program has successfully assessed the robustness of the measurement system in a variety of situations, and provides a strong resource for education of PhD candidates in sophisticated experimental measurements. A further use of this system has been directed toward lightweight inflatable structures, again an area of strong relevance to the research mission of the Air Force for space applications.

The overall objective of this dissertation is to effectively and efficiently obtain some important characteristic functions of acoustic transducers, such as electrical impedance function, transmitting voltage response (TVR) and beam pattern (BP). Oftentimes, one makes measurements on these functions through traditional ways, e.g., stepped harmonic analysis method and Fourier-based analysis method. To improve the accuracy and efficiency of computing these characteristics, new approaches by pole-residue operations are developed and verified in this dissertation. In this new approach, the poles and residues associated with the input and output signals are extracted with the multi-signal Prony-SS method, which is an extension and improvement of the classical Prony’s method. The system functions can be computed by the operations of those poles and residues from input and output signals. Compared with traditional methods, the new one not only turns out effective and computationally efficient but also overcomes the leakage and the frequency resolution problems, by getting a continuous function in the frequency domain without periodic assumption. In addition, many significant characteristics, such as modal frequencies and modal damping, can be precisely calculated from the system poles other than reading them from the plotting of system functions in traditional ways. When a periodic loading excites the linear system, the calculation of transient response is discussed in manuscript 1. Compared with time-domain methods, frequency-domain methods are more computationally efficient when computing the responses of linear dynamic systems. However, frequency-domain methods can only compute the steady-state response instead of the total response. To the author’s best knowledge, the transient response of a dynamic system to arbitrary periodic loading can not be solved analytically. In the first manuscript, a closed-form solution for the transient responses of linear multi-degree-of-freedom (MDOF) systems to arbitrary periodic excitations is derived. By taking advantage of the fast Fourier transform (FFT) algorithm, a very efficient numerical method is developed to compute the transient and total responses of MDOF systems, suitable for both damped and undamped systems. In the newly developed method, the computational time required for obtaining the transient response is much less than that for the steady state response. Three numerical examples are provided in this manuscript to verify the correctness, and demonstrate the effectiveness as well, of the newly developed method. Discussed in the second manuscript is the impedance function, which is very essential for a transducer. The impedance function contains many important characteristics, such as the resonant frequencies, anti-resonant frequencies, and

Features of heterogeneous dynamic systems, an important class of models employed in different engineering areas, are considered. The classification of events in hybrid dynamical systems is expanded on. The family of complex event detection algorithms is introduced. Requirements to modeling and simulation environments supporting heterogeneous dynamic systems are given. Modern complex dynamic system modeling and simulation environments are tested for satisfaction of the identified requirements.

The technology of the strategic goal-setting and monitoring of a system development on the basis of cognitive mapping

Rotor dynamic response prediction using physics-informed multi-LSTM networks

The traditional frequency domain transfer path analysis has become a popular method to detect and diagnose vehicle NVH problems. Unfortunately, due to its reliance on frequency transfer functions, the approach is strictly effective only for linear time-invariant system and steady-state response. This limitation prevents the method from being applied to transient and/or nonlinear behavior such as clunk, shudder, and tip-in and tip-out. In this paper, a novel time domain transfer path analysis is proposed to deal with a class of non-linear transient response problems. It combines the versatility of the transfer path analysis for tracking transmission of vibratory energy between substructures and generality of the time domain analysis for treating transient response that is also nonlinear in nature. The formulation that is derived by combining the spectral-based substructure method and a discrete, piecewise convolution theory is applied to a lumped parameter system, and the results are compared with output from a direct numerical integration of the nonlinear equations of motion. Comparison results show significant promise and appear to be usable for solving real-life vehicle problems that are highly transient with moderate level of nonlinearity present.

A continuum-based sizing design sensitivity analysis (DSA) method is presented for the transient dynamic response of non-linear structural systems with elastic–plastic material and large deformation. The methodology is aimed for applications in non-linear dynamic problems, such as crashworthiness design. The first-order variations of the energy forms, load form, and kinematic and structural responses with respect to sizing design variables are derived. To obtain design sensitivities, the direct differentiation method and updated Lagrangian formulation are used since they are more appropriate for the path-dependent problems than the adjoint variable method and the total Lagrangian formulation, respectively. The central difference method and the finite element method are used to discretize the temporal and spatial domains, respectively. The Hughes–Liu truss/beam element, Jaumann rate of Cauchy stress, rate of deformation tensor, and Jaumann rate-based incrementally objective stress integration scheme are used to handle the finite strain and rotation. An elastic–plastic material model with combined isotropic/kinematic hardening rule is employed. A key development is to use the radial return algorithm along with the secant iteration method to enforce the consistency condition that prevents the discontinuity of stress sensitivities at the yield point. Numerical results of sizing DSA using DYNA3D yield very good agreement with the finite difference results. Design optimization is carried out using the design sensitivity information. Copyright © 2000 John Wiley & Sons, Ltd.

Discrete dynamic simulation models and technique for complex control systems

Complexity of cities has for centuries been a research question across a wide range of disciplines. Cities are live organisms evolved by interactions of various heterogeneous subsystems. They are not only dynamic but also spatially distributed. Additionally, they involve humans interacting with the physical subsystems (so called cyber-physical systems). Urban planners today face a difficult task of designing new and redesigning the current urban spaces in a way to make them more liveable and walkable (the key objectives of smart cities). Yet those responsible, the city planners or urban designers still only guess about an optimal street design. This paper provides an overview of literature and discussion of potentials of space syntax, technique developed during the last 35 years that proved itself effective in city planning procedures. Space syntax provides a set of theories and methods for analysis of spatial configurations. It allows us to link human societies and space and to describe relations between them. These methods showed immerse potential to a wide range of disciplines and their integration is crucial for the field of smart cities.

Testing of a transfer plate by pseudo-dynamic test method with substructure technique

Our aim is to achieving maintain constant DC voltage in dc micro-grid. Therefore we proposed control scheme to maintain DC bus voltage constant in AC micro-grid under different operating condition via the help of PEC equipment integrated with PV array module and bi-directional DC-DC convertor with storage device (batteries) which behave as similar inertia characteristics DC machine they delivered to the required amount of energy to DCMG for maintaining constant dc voltage and maintain the stability. We also extract the maximum power from PV array module via application of MPPT algorithm under different condition. In this paper battery considered as storage device with bi-directional DC-DC convertor which can stable the unwanted fluctuation occurred on load side and improve dynamic & transient response of the whole system. And finally response analysis of whole system steady state analysis via application MATLAB Simulink and improve the result with proposed control scheme.

The large-scale integration of doubly-fed induction generator (DFIG) based wind power plants poses stability challenges for power system operation. This study investigates the transient stability and dynamic performance of a modified 3-machine, 9-bus Western System Coordinating Council (WSCC) system. The investigation was conducted by connecting the DFIG wind farm to the sixth bus via a low-impedance transmission line and installing power system stabilizers (PSSs) on all automatic voltage regulators (AVRs). A three-phase fault simulation was carried out to test the system, with and without power system stabilizers and a static synchronous compensator (STATCOM) device. Time-domain simulations demonstrate improved transient response with PSS-STATCOM control. A 50% reduction in settling time and 70% decrease in power angle undershoots at the slack bus are achieved following disturbances, even at minimum wind penetration levels. Load flow analysis shows the coordinated controllers maintain voltages within 0.5% of nominal at 60% wind penetration, while voltages at load buses can deviate up to 15% without control. Eigenvalue analysis indicates the PSS-STATCOM boosts damping ratios of critical oscillatory modes from nearly 0% to over 30% under high wind injection. Together, the present findings provide significant evidence that PSS and STATCOM cooperation enhances dynamic voltage regulation, angle stability, and damping across operating ranges, thereby maintaining secure operation in systems with high renewable integration.