Two-substructure, time-domain transfer path analysis of transient dynamic response of mechanical systems with nonlinear coupling.

The transient response sensitivity analysis of the transmission line is a new hotspot problem in transmission line problems. In this paper, a sensitivity analysis method based on fast Fourier transform is proposed in the transient response sensitivity analysis of the transmission line network. The method firstly establishes the circuit equation of the whole transmission line network characteristic, and transforms the partial differential equation in the time domain into the ordinary differential equation in the frequency domain by Fourier transform. Then we find the derivative of a certain distribution parameter of the transmission line by the ordinary differential equation. The network transient response sensitivity problem is transformed into solving the transient response of the transmission line network and the partial derivative of the network parameter matrix to the circuit parameters, which greatly simplifies the analysis of the transient response sensitivity of the transmission line network, and the sensitivity analysis of the transient response of any node of the transmission line network to any network parameters is realized. The method does not need to decouple the coupled transmission line, and can accurately and quickly calculate the transient response sensitivity of any type of transmission line network. The result of the example shows that the method is correct and effective. This method provides a new reference method for the sensitivity analysis of transmission line network transient response.

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

In this paper, discussions were made on using DFT and IDFT to calculate the transient acceleration response of a single degree system. Two key points were discussed: the sampling frequencies and the time span. Simulation were made the transient response of a single degree system's transient response, it was found that the sampling frequencies have the greatest influence on the calculation error. The calculation precision's relation with the sampling frequencies were discussed, it shows that to keep calculation error in 10%, 99% energy in the low frequency should be calculated correctly.

During fast gas-turbine engine acceleration and deceleration, the transient vibration effects in bladed disk vibration become significant and the transient response needs to be calculated. In this paper, an effective method is developed for efficient calculations of the transient vibration response for mistuned bladed disks under varying rotation speeds. The method uses the large-scale finite element modeling of the bladed disks allowing the accurate description of the dynamic properties of the mistuned bladed disks. The effects of the varying rotation speed on the natural frequencies and mode shapes of a mistuned bladed disk and its effects on the amplitude and the spectral composition of the loading are considered. The dependency of the modal characteristics on the rotation speed is based on the evaluation of these characteristics at reference points followed by the interpolation to obtain values at any rotation speed from the operating range. A new method has been developed for the interpolation of mode shapes while preserving the orthogonality and mass normalization of the mode shapes. The method of mode shape interpolation is elaborated for tuned and mistuned bladed disks. The accuracy and efficiency of the method are demonstrated on test examples and on analysis of transient forced response of realistic bladed disks.

Recent literature on building energy performance simulation leans toward implementing uncertainty analysis (UA), instead of deterministic solutions, to handle ever-existing and pivotal uncertainties in building design decision-making process. Variations in weather temperature, degradation of building envelope material properties over time, and random behavior of occupants, among all, are the key sources of uncertainty in building energy consumption predictions. The UA couples to the sensitivity analysis (SA) to identify the most influential inputs on the uncertainties of the building energy consumption. This paper describes a newly-developed UA and SA predictive tool for building energy performance simulations. Energy performance simulations are based on a resistance-capacitance thermal model for the building. For a hypothetical residential building in College Station, Texas, USA, the present work describes and compares predicted probability distribution and sensitivity indexes produced by the UA-SA tool using a transient (dynamic) response analysis (TRA) and static response analysis (SRA). For brevity, the analysis considers uncertainty only for the exterior walls’ parameters including thickness, thermal conductivity, heat transfer coefficient, density, and heat capacity; i.e., a five-dimensional problem is solved. Compared to the TRA, predictions from the SRA underestimate the annual energy consumption up to 30%; however, SRA is significantly faster. Nonetheless, sensitivity indexes from the SRA and TRA closely match.

Taking the high bypass ratio turbofan engines as the research object for the dual-rotor system under the load of blade loss, a simplified four disk dual rotor system is established. The motion differential equation of the dual rotor system is established by the finite element method, and the transient response of the dual rotor system under the blade loss load is simulated and calculated with the Newmark-β integral method, considering the effects of rotor speed, eccentricity, supporting stiffness and damping. The results show that the transient response of the system has obvious impact characteristics under the excitation of the blade loss load, and the stiffness and damping of the bearing at the rear of the fan have a significant influence on the transient response.

On a critique of a numerical scheme for the calculation of fractionally damped dynamical systems

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

In this paper, an experimental and numerical investigation were conducted to develop an understanding of the importance and role played by honeycomb design parameters in transient response of aircraft sandwich with honeycomb core under the transient load. Forced vibration under transient load test was implemented on sandwich panel with honeycomb core specimens. Vibration rig with specific equipment was manufactured. Finite element simulation for the sandwich panel with honeycomb core were developed and analyzed by Ansys software package. Modal analysis and transient response analysis have been carry out to obtain the numerical transient response. The obtained results show a good agreement between above approaches with conformity by 85% percentage. The core high, cell size and cell wall thickness were selected to explore the effect of honeycomb parameters on the transient response of sandwich structure. In order to obtain the optimum condition, Response Surface Methodology (RSM) was used. Results showed that minimum transient response were found at 20 mm core height, 25 mm size cell and 1.5 mm cell wall thickness. Where, the optimal value minimum transient response equal to 0.0019 mm.

The authors have developed a general-purpose simulation system for the design of link mechanisms. Topological and Kinematic analyses have already been referred to in the preceding paper. In this paper, methods for the dynamic analysis of link mechanisms with controllers, such as transient response and vibration analysis, are proposed. Both the characteristics of the control system and the equations of motion of the mechanical system are automatically and simultaneously transformed into nonlinear state equations. In transient response analysis, for example, the responses of joint displacements, etc., are calculated by the numerical integration of these equations. In vibration analysis, the state equations are linearized around the desired trajectory to calculate the eigenfrequency, mode shape, and transfer functions. The proposed methods were applied to an industrial fobot, and the effectiveness of the methods was ascertained.

In addition to the conventional problems of sensitivity, bandwidth, and transient response, the transistor poses several new problems in television IF design due to its power gain mechanism. In particular, the resistive and capacitive components of output impedance dictate that matched power gain can be obtained only at or below matched bandwidth, and definite limits are thereby imposed on the loaded Q of each stage. Data are presented for high-frequency graded base transistors and high-frequency tetrode transistors. The over-all performance of a five-stage video IF is discussed in terms of: 1) single stage data, 2) stability requirements, 3) method of achieving agc, 4) agc and overload characteristics, 5) pole pattern, gain, and transient response, and 6) noise figure.

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.

Transient response testing has been shown to be an economical technique for testing linear macros in mixed-signal systems. Previously reported work on the analysis of transient responses has shown how the response from a linear network can be processed to generate a single figure, termed the index of functionality, which is an absolute measurement of device functionality and on which pass/fail decisions are subsequently made. However, if the circuit response is deeply buried in the mixed-signal system, it must first be extracted before it can be processed. The paper details the results of an investigation into the effects of sampling, quantising and extracting transient responses serially through a digital scan path before processing. By understanding the mechanisms by which errors introduced by the sampling and quantisation process manifest themselves in the index of functionality, it is possible to optimise the quantisation parameters for a particular test situation and test to any required standard.

Dynamic response of water-rich tunnel subjected to plane P wave considering excavation induced damage zone

Synthesis of optimal controller for synchronous power system