Frequency Response Analysis Research Articles

Multi-strategy modified INFO algorithm: Performance analysis and application to functional electrical stimulation system

A functional electrical stimulation (FES) system holds a significant importance for the paralyzed individuals as it can help them to perform the tasks they are unable to do. It is crucial to develop an efficient control mechanism for the FES system as it acts on the human musculoskeletal system which presents noise and uncertainties. Therefore, this paper proposes a novel control method for efficient operation of the FES system. In this regard, a proportional-integral-derivative controller with filter (PID-F) mechanism is proposed for the first time in literature for efficient operation of the FES system. Besides, a novel multi-strategy based weighted mean of vectors algorithm (m-INFO) is also developed using a modified opposition-based learning and Lévy flight mechanism together with Nelder-Mead simplex search method. Unimodal, multimodal, low-dimensional and CEC2019 benchmark functions are used to demonstrate the excellent performance of the proposed m-INFO algorithm against several other metaheuristic optimizers. The proposed m-INFO algorithm is then used as an efficient tool to design the PID-F controlled FES system. To achieve optimal tuning, a simple yet effective objective function is also proposed. The excellent ability of the developed m-INFO algorithm-based PID-F controller for FES system is demonstrated through comparative statistical, transient response and frequency response analyses using original weighted mean of vectors, marine predators and moth-flame optimization algorithms based PID-F controlled FES systems.

The effect of an evolutionary algorithm's rapid convergence on improving DC motor response using a PID controller

Mobile robots experience a lot of challenges with path tracking because of the significant problem with DC motor speed control. The particle swarm optimization (PSO) tuned proportional integral derivative (PID) controller is commonly used to control DC motor speed. However, it fails to reach the optimal solution quickly. Therefore, this paper demonstrates the application of the artificial bee colony (ABC) algorithm to tune a PID controller for speed regulation of a DC motor. The proposed approach was used to obtain the optimal PID controller gains (proportional, integral, and derivative) by minimizing the integral of time absolute error (ITAE) as the objective function. The analysis of statistical tests, transients, and frequency responses was conducted to test the rapid convergence of the proposed approach. Also, the performance of the proposed ABC-tuned PID controller has been compared with three variants of the PSO-tuned PID controller. The conducted simulation results and comparison with the proposed ABC controller and variant PSO controllers have shown that the proposed ABC-PID controller is more effective and robust than the variant PSO-PID controllers for the speed control of a DC motor.

Determination of electrochemical impedance of lithium-ion battery from charge curve by wavelet transformation

Lithium-ion batteries (LIBs) are being used as power sources for use in electric vehicles and aircraft, and so on. Early detection technique of battery deterioration is required with the spread adoption of electric vehicles and aircraft. Electrochemical impedance spectroscopy is a powerful method to evaluate the internal state of LIB. We recently have proposed a method to determine the impedance spectra of LIB by wavelet transformation (WT) of the external input and the output signals. In the present paper, the impedance spectra were determined by performing WT on the charge curves of the LIB without an external input signal. A capacitive semicircle and Warburg impedance appeared in the impedance spectrum determined by the WT, which is roughly consistent with the impedance spectrum measured by a frequency response analyzer (FRA). In addition, the new impedance determination method was applied to the evaluation of deteriorated batteries. The diameter of the semicircle increased with fading the battery capacity. Curve fitting was applied to the spectra determined by the WT. The sum of the resistance related to electrode structure, Rc, and the charge transfer resistance, Rct, increased as the capacity loss increased. Moreover, the parameter values were in good agreement with those calculated from the impedance measured using FRA, indicating that this new impedance determination method is useful for evaluation of deteriorated batteries. Furthermore, we emphasize that this method can diagnose the battery deterioration simply by charging the battery.

Analysis of Thermal Crosstalk in Photonic Integrated Circuit Using Dynamic Compact Models

Thermal modeling of photonic integrated circuits (PICs) is required for circuit design and the development of thermal control algorithms. In this work, we present a methodology for obtaining a compact dynamic thermal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$RC$ </tex-math></inline-formula> model of a PIC. PICs are sensitive to thermal coupling, and in this article, it is shown that traditional resistive coupling does not suffice, and a new coupling method is derived. The case study to which the new methodology is applied is a dense wavelength-division multiplexing ring filter with eight channels. With the obtained <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$RC$ </tex-math></inline-formula> model, the computational time is reduced from 5.5 h for finite element simulation to < 1 s for a single-step response. Using the compact model, circuit-level analysis of frequency response is carried out. Because of its high computational efficiency, the compact model opens possibilities for simulating thermal tuning algorithms.

Novel Spiral-Gap Shielding Shell for a Rogowski Current Sensor

Rogowski current sensors play an important role in detecting the condition of electrical power substation equipment. An electromagnetic field shielding shell is necessary for some of these sensors to operate correctly, especially those with large diameters and small heights. These are used for frequency-response analysis in power transformers. In this study, the magnetic-shielding effectiveness of a normal C-type metal shell was tested and simulated. The distribution and direction of the magnetic field were analyzed using finite-element simulation calculations to reveal the reasons for its poor shielding effectiveness. It was found that the magnetic field induced by an interference current crosses the shell and enters its cavity through the gap in its inner wall. Shells with larger inner-diameter-to-height ratios have worse magnetic-shielding effectiveness. Therefore, a novel shell structure with a spiral gap is proposed here. The magnetic-shielding effectiveness of this new type of shell was analyzed by further simulations and verified in experimental tests. The results showed that a shell with a spiral gap has better shielding effectiveness when it has a long gap. In addition, the spiral gap was found not to inhibit the current-measurement function of the sensor. This provides a new approach to the design of electromagnetic shielding shells for Rogowski sensors.

Transmission Lines Impedance Fitting Using Analytical Impedance Equation and Frequency Response Analysis

Rational function approximation is commonly used to fit the transmission line impedance over a wide frequency range. Nevertheless, it is computationally costly and challenging to implement in practical applications due to the high number of approximations required to fit the impedance curve for the high-frequency range. Therefore, a novel fitting method of multiconductor transmission line (MTL) based on the analytical impedance equation of a transmission line using the impedance frequency response measurement is presented in this paper. The proposed fitting method is a function of the transmission line length since it is based on the analytical impedance equation of a finite transmission line. Furthermore, the proposed model uses a constant set of equations and calculated parameters to fit the impedance frequency response for a wide range of frequencies. Moreover, the proposed model parameters are calculated using derived resonance equations and the impedance frequency response measurement. In addition, an algorithm is developed to further fit the proposed model to the impedance frequency response measurement of the transmission line. MTL impedance frequency response is measured using a real-time digital simulator (RTDS). To ensure the accuracy of the proposed model, a comparison between the proposed model and vector fitting (VF) is presented.

Sensitivity Analysis of Random Frequency Responses of Hybrid Multi-functionally Graded Sandwich Shells

Sensitivity Analysis of Random Frequency Responses of Hybrid Multi-functionally Graded Sandwich Shells

Analytical Study of Series Solutions for the ‘Nonlinear Mechanical System’ with Stability Analysis

Any mechanical system can easily be analyzed with the help of proper designing or modeling. All kinematical constrains are also been considered at the time of modeling. Generally the traditional dynamical differential equations are solved to predict the nature of the system. In this work, some typical types of dynamical mechanical system in taken into consideration and further the dynamical equations are being solved using ‘Series Solutions Technique’ for the analysis of the nonlinear system. The solution is consisting of two sections. Using frequency response analysis via simulation, which section of the solution is more suitable or effective for the designing purpose has also been explained in detail. Finally, the local stability analysis of the entire system is studied in detail with proper numerical simulation. Keywords: Nonlinearity, Series Solution, Stability Analysis, Phase Portrait, Frequency Response Function.

Efficient computation of frequency response for non-proportional damped systems

Frequency response analysis is required in many structural dynamic applications. For large-scale problems, the cost of performing a frequency response analysis within a frequency interval of interest can be computationally very expensive and prohibitive, because the evaluation of the structural response for each excitation frequency requires solving a system with complex coefficients. For such purposes, a new method for the frequency response analysis of a non-proportional damped system in the frequency interval 0,ωmax is established. We first determine the lower-order modes in the interval 0,ωmax/ψ and retain the quantity, where ψ is an optional parameter which is greater than zero and less than 1. The default value of ψ is set to 0.5. We then approximate the unknown higher-order mode contributions by using partial sums of the constructed convergent power series of excitation frequency. The number of items in the partial sum is determined adaptively by an iterative algorithm performed at ωmax. The resulting analytical expression for the frequency response is applied to the frequency interval 0,ωmax. Consequently, the frequency response analysis can be fulfilled simply by changing the excitation frequency in the analytical expression. Although the proposed method is derived based on the state space approach, its implementation is transformed to the original space to reduce the computational effort and storage space. The accuracy and effectiveness of the proposed method are illustrated and validated by two numerical examples.

Transient studies of gas transport in porous solids using frequency response method – A conceptual study

The response of a system in a state of equilibrium to a specific perturbation provides information about the processes triggered inside the system. This principle is the basis of the presented measurement method: the frequency response (FR) analysis. A customized apparatus is available to investigate mass transport processes of gases in porous solids. “Conventional” evaluation approaches, such as the characteristic FR functions, can be applied along with the complementary combination of other trending techniques such as numerical simulation. An example of a model developed with COMSOL Multiphysics® is shown. The overview discussion of the mentioned method and how electrochemical impedance spectroscopy and the method of temporal analysis of products complement the FR method in the study of mass transfer in porous materials is presented in this work.

Comparison of methodologies to estimate state-of-health of commercial Li-ion cells from electrochemical frequency response data

Various impedance-based and nonlinear frequency response-based methods for determining the state-of-health (SOH) of commercial lithium-ion cells are evaluated. Frequency response-based measurements provide a spectral representation of dynamics of underlying physicochemical processes in the cell, giving evidence about its internal physical state. The investigated methods can be carried out more rapidly than controlled full discharge and thus constitute prospectively more efficient measurement procedures to determine the SOH of aged lithium-ion cells. We systematically investigate direct use of electrochemical impedance spectroscopy (EIS) data, equivalent circuit fits to EIS, distribution of relaxation times analysis on EIS, and nonlinear frequency response analysis. SOH prediction models are developed by correlating key parameters of each method with conventional capacity measurement (i.e., current integration). The practical feasibility, reliability and uncertainty of each of the established SOH models are considered: all models show average RMS error in the range 0.75%–1.5% SOH units, attributable principally to cell-to-cell variation. Methods based on processed data (equivalent circuit, distribution of relaxation times) are more experimentally and numerically demanding but show lower average uncertainties and may offer more flexibility for future application.

Hierarchical model predictive vibration control for high‐rise structures using semi‐active tuned liquid column damper

Vibration control for high-rise structures has become more important as buildings become more lightweight. Tuned liquid column dampers are an established approach for this problem, as they do not consume high amounts of energy while achieving high damping forces. The natural frequency of tuned liquid column dampers (TLCDs) can be changed semi-actively by modifying their column geometry. As shown by previous studies, this approach increases the control performance of the damper and allows a larger application field. However, this modification simultaneously provokes strong nonlinearities, which need to be addressed for controller design. In this contribution a model-based controller for such TLCDs is proposed, which explicitly accounts for the nonlinear dynamics of the coupled system consisting of a multi-storey structure with a semi-active TLCD. To account for various system dynamics of the structure, a hierarchical nonlinear model predictive controller (NMPC) in combination with a multi-start strategy is formulated. In addition, an extrapolation algorithm is developed to determine an approximation of the future trajectory of the structure's induced excitation load. The excitation trajectory is then incorporated in the NMPC framework. For validation, a frequency response analysis and a case study are conducted on a 20-storey benchmark structure, which is equipped with a semi-active TLCD. The study is carried out in simulation, and the results are compared with passive vibration control. With the proposed hierarchical control, a significant improvement is shown in the reduction of structural vibrations over the relevant spectrum of excitation frequencies up to a mean of 50%.

Turn-to-Turn Short Circuit Fault Localization in Transformer Winding via Image Processing and Deep Learning Method

Frequency response analysis (FRA) suffers from the interpretation of results despite its potential ability to detect faults related to the power transformer windings. This article presents a technique for interpreting frequency responses, which is based on image processing and a deep learning method called graph convolutional neural network (CNN). The proposed procedure transfers frequency responses into 2-D images through a visualization technique. The resulting images are aggregated into a dataset to be used as the CNN input. The proposed technique is applied on frequency responses of two different winding models with short circuit (SC) faults. The SC faults with different intensities are applied on different sections of a simulated ladder model winding and a 20 kV winding of a 1.6 MVA distribution transformer. After determining the frequency response for each faulty case and applying the visualization technique, the precise locating of the SC faults is performed by the CNN. Then, the results are analyzed by performance evaluation metrics. At this stage, the high performance of the CNN in the use of 2-D images instead of the conventional method is observed. Finally, by testing the high impedance SC faults in different sections of the simulated winding model and applying the suggested method step by step, early detection of the SC fault is also performed in this article. It should be noted that the suggested technique, in addition to its accuracy and high detection speed, can be considered as an important step in automatic interpretation of frequency responses for online monitoring of transformers.

Capacity fade detection in lithium-ion batteries using non-linear frequency response analysis (NFRA) under multiple open-circuit voltages (OCVs)

Determination of residual capacity, or ‘state of health’ (SOH), is important for the management of battery assets in service and when assessing batteries for re-use at the end of service. Nonlinear frequency response analysis (NFRA) has recently been demonstrated as a means to determine SOH, but the effects of temperature and state-of-charge (SOC) on battery NFRA measurements are not yet well understood. In this work, we investigate the effects of SOC on NFRA measurements performed on commercial 21700 cylindrical cells aged under different temperatures to various SOHs. Total harmonic distortion (THD%) is proposed as a capacity fade indicator. THD% in the range of 10 Hz–150 Hz are found to correlate well with SOH at all SOCs. For frequency < 1 Hz, the effect of aging on THD% is SOC dependent, with larger THDs for the new cell at low open-circuit voltages (OCVs) (2.75 V–3.2 V), and larger THDs for aged cells at higher OCVs (3.5 V–4.1 V). This work also demonstrates the feasibility of NFRA to distinguish between cells that have been aged differently based on temperature.

Uncertain frequency response analysis of clamp-pipe systems via the coordinate transformed polynomial chaos expansion

The frequency response function (FRF) that links structural responses and external excitations is required to realize the dynamic analysis of a clamp-pipe system. Due to random geometry and stiffness parameters, the FRF becomes a stochastic quantity that is represented by a surrogate model based on the polynomial chaos expansion (PCE) in this paper. Considering that an FRF trajectory is mainly controlled by resonance and anti-resonance frequencies, a reference frequency coordinate characterized by the controlling frequencies associated with a nominal value of input random variables is first determined. By reserving the original amplitude, an FRF sample is projected to the reference coordinate through a linear transform. Then, a PCE surrogate model with coefficients estimated by the Gauss-quadrature scheme is obtained, and the utility of an inverse transform allows one to obtain the predicted FRF result in the original domain. Together with estimations on the confidence intervals and extreme boundary results, engineering applications are demonstrated by the uncertain FRF analysis of straight and L-shape clamp-pipe systems.

Ladder Network Synthesis in Wide Frequency Range for Transformer Winding From its Driving-Point Admittance Data

Ladder network synthesis is very significant for winding fault diagnosis within transformer. To synthesize the network reversely based on the measurable frequency response analysis (FRA) data is the only applicable way. To date the iron core and non-tested winding, which result in the frequency-dependent network components and multiple ladders in some frequency ranges, are usually not considered in the reverse process and thus the synthesis precision is largely limited. This paper proposes to synthesize multiple ladder networks in different frequency regions to handle this problem. Firstly, the sensitivities and frequency-dependent features of network components are analyzed, based on which the topology and components of the networks in diverse frequency ranges are determined afterwards. Further, the network synthesis strategies in different frequency ranges are elaborately designed. Finally, the synthesis method is applied on a distribution transformer successfully, with the fact that the extracted network parameters meet all the constraints and its FRA curve matches well with the measured one. An intact method of multiple-network synthesis for transformer winding in wide frequency range, considering the iron core and non-tested winding, is offered in this paper.

Approach for Identification of Inter-Turn Fault Location in Transformer Windings Using Sweep Frequency Response Analysis

As inter-turn faults in transformer windings are the most severe, their delayed detection and localization may create extensive damage to the winding. Therefore, a new inter-turn fault localization methodology based on sweep frequency response analysis (SFRA) through calculation of Pre-fault Inter-Turn Fault Factor ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ITFF_pre</i> ) for all possible fault locations by estimating the values of series and shunt capacitance of the windings during healthy conditions is presented. For a faulty transformer, Post-fault Inter-Turn Fault Factor ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ITFF_post</i> ) is calculated by determining the value of equivalent capacitance using SFRA. The exact fault location in the faulty transformer is obtained by comparing the single calculated value of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ITFF_post</i> of the faulty transformer with the values stored in the lookup table. The efficacy of the suggested approach is verified by performing faults at various locations on the transformer model developed in the laboratory. Its authenticity is also verified on an existing 400 kVA, 11 kV/440 V distribution transformer installed in the real field. The results indicate that the suggested method is capable to identify inter-turn fault location with the minimum ladder network parameters. Finally, a relative assessment of the suggested approach with numerous other methods confirms the superiority in terms of inter-turn fault localization.

Effects of power transformer high-frequency equivalent circuit parameters non-uniformity on fault diagnosis using SFRA test

The electric power transformer is an essential component of an electrical power system because it regulates the voltage level to provide the best possible system operation. Thus, it is important to detect the transformer faults to maintain its reliability as high as possible. The sweep frequency response analysis (SFRA) test is one of the tests which, used to diagnose transformer faults. It determines the fault type by analyzing its response across a wide frequency range. The main advantage of the SFRA test is the detection of mechanical deformation faults since mechanical deformation faults cause the high-frequency equivalent circuit parameters to change which, could be detected easily using the SFRA test. Also, statistical features are defined for this SFRA response used in fault detection and classification. The transformer high-frequency equivalent circuit parameters are non-uniform distributed over discs due to normal leakages and aging. Thus, in the present paper, the non-uniform distribution of the transformer high-frequency equivalent circuit is studied in the SFRA test at different faults and various non-uniformity levels. Finally, when considering the non-uniform distribution of high-frequency equivalent circuit parameters, the results demonstrate that some features are greatly affected, and others are just minimally affected. Depending on how much each feature is affected by the uniformity of high-frequency equivalent circuit parameters, rules of fault diagnosis algorithms based on the SFRA test could be reweighted to improve their accuracy. Also, the obtained results could be compared to real measured data to estimate the actual non-uniformities of transformer parameters.

The Effect of Porous Media on Wave-Induced Sloshing in a Floating Tank

Placing porous media in a water tank can change the dynamic characteristics of the sloshing fluid. Its extra damping effect can mitigate sloshing and, thereby, protect the integrity of a liquefied natural gas tank. In addition, the out-of-phase sloshing force enables the water tank to serve as a dynamic vibration absorber for floating structures in the ocean environment. The influence of porous media on wave-induced sloshing fluid in a floating tank and the associated interaction with the substructure in the ambient wave field are the focus of this study. The numerical coupling algorithm includes the potential-based Eulerian–Lagrangian method for fluid simulation and the Newmark time-integration method for rigid-body dynamics. An equivalent mechanical model for the sloshing fluid in a rectangular tank subject to pitch motion is proposed and validated. In this approach, the degrees of freedom modeling of the sloshing fluid can be reduced so the numerical computation is fast and inexpensive. The results of the linear mechanical model and the nonlinear Eulerian–Lagrangian method are correlated. The dynamic interaction between the sloshing fluid and floating body is characterized. The effectiveness of the added porous media in controlling the vibration and mitigating the sloshing response is confirmed through frequency response analysis.

ORMOSIL Coatings Enriched with CeO2 (5-ATDT)-Ceramic Nanocontainers for Enhanced Protection of HDG Steel Used in Concrete.

This paper reports developing an innovative method of anticorrosion protection based on organically modified silica (ORMOSIL) enriched with CeO2 ceramic nanocontainers loaded with 5-amino-1, 3, 4-thiadiazole-2-thiol (5-ATDT) on hot-dip galvanized zinc (HDG) steel used to strengthen cement in concrete. The chemistry of ORMOSIL coatings and the production of CeO2 ceramic nanocontainers are described in detail for reproduction by other researchers. The anticorrosion properties of these novel coatings were investigated through frequency response analysis (FRA). As a result, the coatings HDG-ORMOSIL + CeO2 (5-ATDT) were better than the samples of HDG steel, HDG-ORMOSIL, and HDG-ORMOSIL + CeO2 (EMPTY) by a factor of 1033.60, 109.21, and 7.76 in terms of anticorrosion protection, respectively.