Coupling Transfer Functions Research Articles

Free vibration analysis of closed and open horizontal cylindrical shells utilizing coupled transfer function method and differential transform method

This article aims to analyze the free vibration of closed and open horizontal circular cylindrical shells based on the concept of state-space transformation in conjunction with the differential transform method (DTM). The governing equations of the cylinders were developed based upon Sanders’ thin shell theory. Then, the set of coupled governing differential equations transformed into nine first-order differential equations. Afterwards, the well-established semi-analytical scheme so-called DTM was employed to solve the differential equations. The numerical investigation of the present method was also comprehensively carried out by analyzing some closed and open cylindrical shells with different boundary and compatibility conditions. To ensure the correctness of the results, the outcomes were compared with experimental and other numerical results, especially with the well-known finite element method. Furthermore, some plots of two-dimensional and three-dimensional mode shapes for the first and second axial modes are depicted.

Research on the Coupled Modulation Transfer Function of the Discrete Sampling System with Hexagonal Fiber-Optic Imaging Bundles

In this study, we developed a numerical model of the coupled modulation transfer function (coupled-MTF) based on the discrete sampling system from the perspective of optical system imaging quality evaluation for coupled two-dimensional discrete sampling characteristics of the hexagonally aligned fiber-optic imaging bundles and CCD image elements. The results show that when the spatial frequency of the input target signal deviates from the Nyquist frequency by 1%, an increase in the number of fibers leads to a faster convergence of the oscillation of the coupled-MTF, and the coupled-MTF converges to a stable value when the number of fibers reaches 1000 × 1000. The deviation of the spatial frequency of the input target signal from the Nyquist frequency is within 1%, and the oscillatory convergence of the coupled-MTF accelerates with increasing deviation. The coupled-MTF oscillates with the deviation period of the wave peak of the input target signal from the initial position of the fiber center, and the theoretical oscillation spatial period is twice the fiber diameter. This study produces important guidelines for the selection of the number of fibers, input spatial frequency, and initial position deviation of the hexagonally arranged fiber imaging bundles.

Study of Capacitive Coupling Sensor Fused With High Voltage XLPE Cable Joint

A capacitive coupling sensor for partial discharge detection with the fusion of high voltage XLPE cable joint is designed in this paper. The sensor is to address partial discharge signals leading to transmission attenuation and external interference causing poor field detection sensitivity. First, a coaxial waveguide transmission model was established of high-frequency electrical signals in the body and joint. The result showed that the signal transmission attenuation was minimized while the sensor electrodes were closely attached to the outer semi-conductive layer of the body. Second, the equivalent circuit model was constructed of the capacitive coupling sensor fused with the 110 kV straight passing joint. The specific installation location, main structure size, detection bandwidth, and sensitivity of the sensor in the joint area were determined, which was to maximize the coupling output signal amplitude and transfer function amplitude. Finally, a lightning surge voltage test was carried out with the integration of the fusion of the joint voltage thermal cycling. Simulation and measurement show the following: while the sensor is installed in the cable metal sleeve break and the electrodes are closed to the overall semi-conductive layer, there is excellent performance for partial discharge detection in the frequency range of 1–300 MHz, with a sensitivity of 5 pC.

Study on Multivariable Decoupling Control of Small PWR Pressurizer based on Active Disturbance Rejection Control

Since the pressurizer (PZR) in a small pressurized water reactor (PWR) features non-linearity, time-dependence, and strong coupling, its accurate mathematical model is hard to build and the traditional control method cannot provide a satisfactory control effect. Therefore, this study describes a multivariable decoupling control method based on the active disturbance rejection control (ADRC) technique for such PZR. In this study, a non-equilibrium three-region model of PZR is built, and processed linearly based on the perturbation theory to generate the pressure and water level coupled transfer function equation. Then, an ADRC based decoupling controller is designed based on the transfer function, and the parameters of the controller are subjected to multi-objective optimization via differential evolution. Finally, the ADRC based decoupling control and traditional proportional-integral-derivative (PID) control for the same small reactor PZR are compared and analyzed by the MATLAB simulation platform. As demonstrate by the comparison, the ADRC based decoupling controller can effectively solve the PZR pressure and level coupling problem and has better robustness and interference immunity than the traditional PID controller. Therefore, this study provides a theoretical foundation for the engineering application of the ADRC method to the PZRs.

Coupled transfer function model for the evaluation of implanted cables safety in MRI.

Multiple medical-device leads implanted next to each other are often encountered in clinical practice. The aim of this work is to study a coupled transfer function model to evaluate the safety of these coupled leads submitted to the RF field of a 1.5T MRI scanner for a constant distance between both leads. The effect of coupling on the heating of 2 cables with different termination conditions is evaluated experimentally. The coupled and single transfer functions are determined experimentally and used to predict the relative temperature increases of both cables alone and coupled. Two different coupled models, an additive model and a global model, are proposed. The coupled transfer functions are also simulated. The coupling between cables has a strong influence on the resulting heating at the electrodes. The coupled additive transfer function model is a relevant tool to evaluate the heating of coupled leads separated by a constant distance. The global model underestimates the heating in one of the coupled cases by about 30%. The measured coupled transfer functions coincide with the simulated models. It is necessary to take into account the coupling effect between leads to evaluate the safety of implanted devices. This work shows that, in the case of 2 cables separated by a constant distance, that an experimentally determined coupled transfer function allows estimation of the heating of the 2 electrodes for a given incident field. Further work should take into account the in vivo varying distance between the 2 cables.

The cross-coupling problem caused by the structure of a combined radial-axial magnetic bearing for DC motors

Different from separated magnetic bearing units, combined radial-axial magnetic bearing (CRAMB) has cross coupling problem caused by structure itself. This paper focuses on the study of cross coupling problem for a CRAMB caused by structure itself. An equivalent magnetic circuit model (EMCM) considering the leakage and coupling effects was presented to analyze the mechanism of cross coupling. The analysis results show that due to the influence of magnetic flux leakage and common bias magnetic circuit, cross coupling between axial and radial direction caused by the structure itself of a CRAMB cannot be ignored. The coupling degrees of factors that cause cross coupling are analyzed based on the combination of EMCM and finite element method (FEM). The analysis results show that the coupling effect caused by axial magnetic flux leakage was most serious. To solve the coupling problem caused by the structure itself, the coupled transfer function is derived. This coupled transfer function has been added in the original controller. Experimental results show that the cross coupling effect was reduced effectively and CRAMB can levitate the rotor at 48000 r/min stably with the improved controller.

Numerical study on Kerr frequency comb generation in Si3N4 microresonators with frequency-dependent access coupler properties

Within the framework of vertically coupled silicon nitride (Si 3 N 4) resonators characterized by 220 GHz free spectral range driven by a continuous wave laser at 1.55 µm for Kerr comb generation, severe issues may arise in the design of achromatic critically coupled resonators because of the difficulty in designing dispersion-free access couplers with controlled coupling factor over a large spectral bandwidth. As a consequence, numerical simulations of Kerr frequency comb in these structures may drastically differ from reality if frequency dependence of the access coupler's properties is not taken into account in the simulated model. In order to address this issue, we have developed a numerical model that takes into account the frequency dependence of the access coupler coefficients and remains valid even for the simulation of low Q factor resonators. Field propagation within the ring is described by nonlinear Schrodinger equation. The novelty of this model lies in the computation of a complex-valued, frequency-dependent coupling transfer function between a resonant ring and underlying access waveguide that models frequency-dependent dispersion and losses in the access-coupling region of the resonator. Based on simulation results, we discuss the differences observed in Kerr comb generation in resonators with three different coupler designs initially intended to yield critical coupling over the largest achievable bandwidth.

A Transfer Function Based Calculation Method for Radio Frequency Interference

A transfer function based calculation method is proposed to estimate radio frequency interference (RFI) problems. The closed-form equations are analytically derived from Maxwell's equations and the reciprocity theorem. The derived equations can clearly decompose the RFI problem into two parts: the noise source and the coupling transfer function to the antenna. Based on derivations, a transfer function concept is proposed to quantify the coupling coefficient from each unit dipole moment to the victim antenna. The transfer functions can be easily obtained from S -parameter measurements. The proposed method is validated through numeric simulations and real cellphone experiments. Engineering insights drawn from the method are also discussed. Overall, the proposed method is accurate, fast, and can provide physical insights for practical designs.

Coupled Microvibration Analysis of Space Optical Load Platform

This paper investigates the microvibration induced by a pulse tube cryocooler mounting on a space camera, and it describes a full methodology and experimental verification to deal with microvibration predictions. A coupled transfer function matrix is introduced by improving the traditional disturbance model, which is apt to be more representative of the real boundary conditions. The coupled method corrects the microvibration input load by using force filters that depend on estimations of the interface accelerances. The impact of microvibration is predicted, based on transfer functions found from the modeled camera. A system-level microvibration test is performed to verify the predicted results. Dynamic coupling is shown to exist. After integrating the finite element analysis results with the optics design software, the performance of the optical system represented by the modulation transfer function is analyzed. The results show that the surface deformations caused by cooler microvibration are very small, which can be neglected compared with the rigid-body motion. This approach accurately predicts the microvibration and its influences, which provides a new way to analyze the microvibration of an optical load on spacecraft.

The application of proportional–integral–derivative–type fuzzy controller for synchronized XY motion gantry stage system

Gantry systems in which two linear motors are used to drive a single axis provide flexible and efficient solutions for a wide range of material handling applications. It is an important issue to find a way to drive the parallel stage to achieve a synchronous motion effectively and precisely. In this research, the proportional–integral–derivative–type fuzzy controller structure is presented for precision trajectory tracking control in synchronized XY motion gantry stage system. Three proportional–integral–derivative–type fuzzy controllers are designed for each axis, and the complete membership functions and rule table are developed to fulfill the better tracking capability. The controller parameters, which include the scaling factor of fuzzy rules and proportional–integral structures, are searched using the cross-mixing global artificial bee colony algorithm. The algorithm can optimize these parameters based on the integral of the time-weighted absolute error criterion. MATLAB system identification tool is used to find the equivalent coupled transfer functions of the gantry system. The proposed cross-mixing global artificial bee colony algorithm is utilized to offer the better convergence speed and avoid the local optimal solution in the searching process. The simulation results and experimental results on star and circle reference contours are presented to show that the proposed cross-mixing global artificial bee colony–based fuzzy controller indeed accomplish the better tracking performances in motion control application.

Coupled disturbance analysis of a pulse tube cryocooler

To predict accurate micro-vibration produced by a spaceborne payload mounted pulse tube cryocooler (PTC), a coupled disturbance analysis of cryocooler with flexible support structures have been discussed and investigated. A coupled transfer function matrix is introduced by improving the traditional disturbance analysis. According to the coupling disturbance relationship between the source and supporting structure, microvibration input load is accurately obtained. Based on the finite element model of the space camera, the performance of optical system is analyzed. Compared to the decoupled method, this coupled method can accurately predict the local transfer characteristics between cryocooler and interface.

Relationships between the decoupled and coupled transfer functions: Theoretical studies and experimental validation

Abstract A generalized method for predicting the decoupled transfer functions based on in-situ transfer functions is proposed. The method allows predicting the decoupled transfer functions using coupled transfer functions, without disassembling the system. Two ways to derive relationships between the decoupled and coupled transfer functions are presented. Issues related to immeasurability of coupled transfer functions are also discussed. The proposed method is validated by numerical and experimental case studies.

Power Systems Stability through Piecewise Monotonic Data Approximations – Part 1: Comparative Benchmarking of L1PMA, L2WPMA and L2CXCV in Overhead Medium-Voltage Broadband over Power Lines Networks

This first paper assesses the performance of three well-known piecewise monotonic data approximations ( i.e. , L1PMA, L2WPMA, and L2CXCV) during the mitigation of measurement differences in the overhead medium-voltage broadband over power lines (OV MV BPL) transfer functions. The contribution of this paper is triple. First, based on the inherent piecewise monotonicity of OV MV BPL transfer functions, L2WPMA and L2CXCV are outlined and applied during the determination of theoretical and measured OV MVBPL transfer functions. Second, L1PMA, L2WPMA, and L2CXCV are comparatively benchmarked by using the performance metrics of the percent error sum (PES) and fault PES. PES and fault PES assess the efficiency and accuracy of the three piecewise monotonic data approximations during the determination of transmission BPL transfer functions. Third, the performance of L1PMA, L2WPMA, and L2CXCV is assessed with respect to the nature of faults — i.e. faults that follow either continuous uniform distribution (CUD) or normal distribution (ND) of different magnitudes—. The goal of this set of two papers is the establishment of a more effective identification and restoration of the measurement differences during the OV MV BPL coupling transfer function determination that may significantly help towards a more stable and self-healing power system. Citation:  Lazaropoulos, A. G. (2017). Power Systems Stability through Piecewise Monotonic Data Approximations – Part 1: Comparative Benchmarking of L1PMA, L2WPMA and L2CXCV in Overhead Medium-Voltage Broadband over Power Lines Networks. Trends in Renewable Energy , 3(1), 2-32. DOI: 10.17737/tre.2017.3.1.0029

Stability analysis for coupled multilayer graphene nanoribbon interconnects

Based on equivalent single conductor (ESC) concept for multilayer graphene nano-ribbons (MLGNRs), this paper establishes the distributed transmission line model of coupled MLGNR interconnects and derives the analytical expression of coupled transfer function. Using the proposed model and Nyquist stability criterion at the global level of 14nm technology node, the impact of switching factor and various design parameters on the relative stability and crosstalk delay of the coupled interconnects is investigated. It is shown that crosstalk effect makes the coupled interconnect system more stable than that in a single interconnect case. Moreover, increasing the wire length and edge roughness, the coupled interconnects becomes more stable due to the raise in crosstalk delay. Whereas, the increase of wire width, space and doping density, the crosstalk delay decreases, and the coupled interconnects is less stable. The time response for the step input verifies the analysis mentioned above. The results presented in this paper are useful for the design of reliable MLGNR interconnects with better propagation characteristics.

An admittance shaping controller for exoskeleton assistance of the lower extremities

We present a method for lower-limb exoskeleton control that defines assistance as a desired dynamic response for the human leg. Wearing the exoskeleton can be seen as replacing the leg's natural admittance with the equivalent admittance of the coupled system. The control goal is to make the leg obey an admittance model defined by target values of natural frequency, peak magnitude and zero-frequency response. No estimation of muscle torques or motion intent is necessary. Instead, the controller scales up the coupled system's sensitivity transfer function by means of a compensator employing positive feedback. This approach increases the leg's mobility and makes the exoskeleton an active device capable of performing net positive work on the limb. Although positive feedback is usually considered destabilizing, here performance and robust stability are successfully achieved through a constrained optimization that maximizes the system's gain margins while ensuring the desired location of its dominant poles.

English

In this paper we designed an adaptive decorrelator which is based on two cross coupled least-mean square algorithms. This decorrelator is used to remove the crosstalk which may occur during echo in telephone networks, while two or more persons talking at the same time. This paper deals with separation of two sound (voice) signals which are mixed in real environment. This separation is done by decorrelating cross coupling transfer functions which link the two sound signals. The decorrelator is implemented using LabVIEW, since it is convenient for implementing such algorithms. Here LMS algorithm starts with weight vector zero and iteration continues till the error is minimized. This work has application in smart phones, hearing aid systems and speech recognition systems.

Building simulation model of infant-incubator system with decoupling predictive controller

This paper introduces theoretical modelling working on the thermal behavior of the premature infant. This study aims at developing a model useful for the prediction and design of the appropriate controller in objective to reduce evaporative heat loss. A calculation code has been developed to simulate the thermal response of a premature baby to climatic solicitation inside the incubator system. The model allows us to take into consideration radiative, conductive, convective, and evaporative heat transfers inside the incubator system. The air temperature and the humidity rate, which play a salient part in the convective and evaporative exchanges, are calculated by a coupled transfer function. At present, the environmental conditions (temperature and humidity) inside incubator are controlled with a classical Proportional Integral Differential (PID). In this work, we proposed a decoupling Generalized Predictive Controller (DGPC) based on the model described below to achieve an optimal thermal conditions (36.5–37.5) for immature newborn infants (birthweight <1000grams). Real and simulations results prove the feasibility and effectiveness of the proposed model and controller.

A simulation method for lightning surge response of switching power

In order to meet the need of protection design for lighting surge, a prediction method of lightning electromagnetic pulse (LEMP) response which is based on system identification is presented. Experiments of switching power's surge injection were conducted, and the input and output data were sampled, de-noised and de-trended. In addition, the model of energy coupling transfer function was obtained by system identification method. Simulation results show that the system identification method can predict the surge response of linear circuit well. The method proposed in the paper provided a convenient and effective technology for simulation of lightning effect.

A Stochastic Texture-based Approach for Evaluating Solute Travel Times to Groundwater at Regional Scale by Coupling GIS and Transfer Function

Interpreting and predicting the evolution of non-point source (NPS) pollution of soil and surface and subsurface water from agricultural chemicals and pathogens, as well as overexploitation of groundwater resources at regional scale are continuing challenges for natural scientists. The presence and build up of NPS pollutants may be harmful for both soil and groundwater resources. Accordingly, this study mainly aims to developing a regional-scale simulation methodology for groundwater vulnerability that use real soil profiles data. A stochastic approach will be applied to account for the effect of vertical heterogeneity on variability of solute transport in the vadose zone. The approach relies on available datasets and offers quantitative answers to soil and groundwater vulnerability to non-point source of chemicals at regional scale within a defined confidence interval. The study area is located in the Metaponto agricultural site, Basilicata Region-South Italy, covering approximately 12000 hectares. Chloride will be considered as a generic pollutant for simulation purposes. The methodology is based on three sequential steps: 1) designing and building of a spatial database containing environmental and physical information regarding the study area, 2) developing travel time distributions for specific textural sequences in the soil profile, coming from texture-based transfer functions, 3) final representation of results through digital mapping. Distributed output of soil pollutant leaching behavior, with corresponding statistical uncertainties, will be visualized in GIS maps. Of course, this regional-scale methodology may be extended to any specific pollutants for any soil, climatic and land use conditions.

Receptance Coupling for Micro-End-Milling

Micro-end-milling tools are suitable for machining miniature parts which have complex shape. As the diameters of tools are too small, cannot directly obtain the frequency response functions (FRFs) through impact hammer test at tool tip. This paper employs Receptance Coupling method (RC), couple the tool tip’s FRFs with machine-toolholder system’s FRF, and then get the micro-end-milling tool’s FRF. Establish the coupling model, then finite element and hammer test of the blank gauge tools are used to obtain the coupling transfer functions (TFs). Then analyze the tool tip model by finite element, couple with the machine-toolholder system hammer test result and coupling transfer functions, finally the micro-end-milling tool’s FRFs are obtained. Through the hammer test of blank gauge tool, the effectiveness and feasibility of RC method are verified. The result shows that the RC method is accurate at micro-end-milling tool in steady state milling.