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Modelling of smart intelligent materials with PZT & PVDF sensors / actuators to control the active vibrations of flexible aluminum mechanical cantilever beams using PID techniques is presented in this research article. A multi input multi output beam (flexible cantilever beam) is considered as the single point of attraction and this is the plant, which is to be subjected to the vibrations, this could be treated as the wing of an aircraft attached to the hub. The flexible mechanical aluminium cantilever beam is subjected to vibrations, say an external force being acted upon by the wind pressure or an exciter. Smart materials have got some special properties that react to the changes in their environmental conditions. The beam is subjected to vibrations. These vibrations should be suppressed in no time, else, the plant may get damaged. Hence, we put piezoelectric (PZT) and poly vinyl derylene fluoride (PVDF) sensor and actuators at 2 different positions to sense the vibrations and act upon immediately to neutralize it. The PZT sensors sense the vibrations & the actuators give an actuating signal to the controller, which in turn generates anti signals to neutralize the effect of the primary source of vibration. We have used the multi-sensor data fusion concept as if we use the same sensor and actuator, we may not get good results. Mathematical modelling of sensor and actuators of the 2 types is done, this is used to design the PID controller to suppress the vibrations in no time. The paper shows the effect of the multi sensor actuator pair of smart intelligent materials used in the vibration suppression. The work done can also compared with others to show the authenticity or the profoundness of the methodology proposed with the help of materials used in the theory of material science.

Considering the higher flexibility in tuning process and finer control action of the fractional-order proportional integral derivative (FOPID) controller over the conventional proportional integral derivative (PID) controller, this paper explores its application in the automatic voltage regulator system. FOPID contains five tuning parameters as compared to three in the conventional PID controller. The additional tuning knobs in FOPID provide increased control flexibility and precise control action, however, their inclusion makes the tuning process more complex and tedious. Thus, the intelligence of an artificial intelligence (AI) technique called jaya optimization algorithm (JOA) is utilized in order to obtain an optimal combination of FOPID gains which further led to the optimal transient response and improved stability of the considered AVR system. To validate the performance superiority of the proposed approach its corresponding system’s dynamic response is compared with that of the other well-known AI-based approaches explored in recent literature. Furthermore, the stability study of the proposed AVR system is carried out by evaluating its pole/zero and bode maps. Finally, the robustness of the proposed optimized AVR system against the system’s parameter variation is evaluated by varying the time constants of all the four components of AVR (generator, exciter, amplifier and sensor) from −50% to +50% independently. The proposed algorithm based FOPID tuning technique provides 59.82%, 56.09%, 14.94%, 34.24%, 35.70%, 21.64%, 12.0%, 41.33%, 14.84% and 15.17% reduced overshoot than that of differential evolution (DE), particle swarm optimization (PSO), Artificial Bee Colony (ABC), Bibliography Based Optimization (BBO), Grasshopper Optimization Algorithm (GOA), Pattern Search Algorithm (PSA), Improved Kidney Inspired Algorithm (IKA), Whale Optimization Algorithm (WOA), Salp Swarm Algorithm (SSA) and Local Unimodal Sampling (LUS) algorithm respectively, thus validates its competence and effectiveness.

Within this work, a novel controller in terms of H infinity ( H ∞ ) and structured singular value decomposition has been presented to provide the robust performance of the Automatic Voltage Regulator (AVR) system Six real structured uncertainties in actuator, exciter and generator have been assumed for the linear transfer functions of the AVR system. Each uncertain parameter varies between a minimum and a maximum value due to the load variations in a period of time and aging effects over the life time. The efficiency of the presented design lies on two main reasons. The first is the simultaneous considering of the output disturbances, sensor noises and system uncertainties in the controller design approach. The second is the non-conservative modeling of all six structured parameters in the required μ -synthesis P − Δ − K configuration. By suboptimal H ∞ control design technique and μ -analysis theorem, a single input single output (SISO) controller comprising a closed loop system with μ

Tractor overturning is a leading cause of fatalities for farmers. In Japan, small tractors are used for farming on harsh terrain, such as slippery fields and steep passage slopes. On such potentially dangerous terrain, steering instability induced by bouncing and sliding can cause tractor overturning accidents. Steering instability can also deteriorate the precision of trajectory tracking in autonomous driving tractors. The present study numerically investigated tractor steering instability due to bouncing and sliding. A bouncing model and bicycle model were coupled based on Coulomb's classical theory of friction, and numerical experiments were conducted using the developed model. In the simulations, the tractor's travel velocity, the static friction coefficient, the bump length, and the turning radius were considered as control parameters. A turning test was conducted to investigate the basic steering performance of the developed model. The numerical results revealed that the bouncing and sliding caused by the disturbance exciter reduced the cornering force to zero, which led to a deviation of the turning trajectory from the desired trajectory. The tractor was then operated on a steep passage slope similar to those reported in accidents in Japan. In the simulation, bouncing and sliding occurred because of the steep slope. The results obtained in this study strongly suggest that bouncing and sliding occurring on specific terrain result in steering instability and are a major cause of overturning accidents.

The Automatic Voltage Regulation (AVR) system which works within the synchronous generator[s] locally is defined as the closed loop control system that keeps the reactive power output at demanded value by adjusting exciter signal. Designing a proper control scheme for the AVR system to provide the desired level of voltage stability is an important research field. Nowadays, classic 1DOF PI-controller which takes into account only the load side disturbance is generally used in the AVR systems. In this study, to improve the robustness of this system towards the relatively severe disturbances caused from both load side and set point side, the 2DOF state feedback PI-controller which is tuned with a meta-heuristic optimization algorithm is proposed. Since only the error signal is minimized by using a simple cost function, this method can be applied simpler as independent to the system parameters, optimal coefficients are computed simpler. The superiority of the proposed controller is proved by applying stability, time-domain, frequency-domain and two different robustness analyses such as instantaneous and continuous disturbance analyses. It is observed from these analyses that the maximum overshoot and settling time obtained from the proposed control structure decrease more than a half. In addition, the immunity towards instantaneous and continuous disturbances significantly improve and the step responses in these cases stay in 2% band. At the end of the study, the implementation proposal related to the new control scheme is presented and interpreted in detail.

The purpose of this study is to investigate the synchronization of an exciter and two cylindrical rollers (CRs) in a super-resonant vibrating system. The averaging method of modified small parameters is exploited to construct the synchronization criterion of two CRs and an exciter. The Routh-Hurwitz criterion is used to derive the stability conditions of the synchronization process. The synchronization criterion is then discussed numerically, as well as the abilities of synchronization and stability. The numerical results can provide a theoretical basis for an engineering design. Finally, computer simulations are carried out to verify the results of the theoretical investigation. Additionally, the numerical and simulation results show that the structure of the vibrating system can ensure the stability conditions of the synchronization process.

The use of a non-contact electromagnetic excitation system is highly recommended in the literature to identify the mechanical properties of materials using the Oberst Beam Method. However, it is not possible to test a specimen made of non-magnetic material using the Oberst beam test rig, comprising of an electromagnetic exciter, unless the specimen is modified using some magnetic particles or small discs made of a ferromagnetic material. Although doing so makes it possible to perform the test, this results in an undesirable modification to the test specimen, leading to unquantified levels of errors in the estimated material properties. This study proposes an approach for eliminating the adverse effects of such mass modification to the test specimen, and also allows subsequent removal of the electromagnetic stiffening effects produced by the electromagnetic exciter. The proposed method is validated using both finite element (FE) simulations and experimental data. Results confirm that the proposed method for the removal of the adverse effects of mass modification, combined with the subsequent removal of the electromagnetic stiffening effects, is very effective, making it possible to determine the material properties of non-magnetic materials with a very good accuracy.

In recent years, a lot of developments can be seen in the field of local defect resonance (LDR) based thermosonics which provide thermal image of a defect by exciting the structure at particular defect frequencies. LDR based thermosonics is found to be more promising compared to traditional thermosonics due to its high reproducibility and low power usage. However, fast and accurate detection of these LDR frequencies is a challenging task. In this context, this paper addresses a fast and reliable method of LDR frequency determination using bicoherence plots. Two exciters and one receiver PZTs (lead zirconate titanate) are used for the experiment. One exciter PZT is provided with chirp or Gaussian white noise signal input while a fixed frequency signal is given to the second exciter PZT. Intermodulation of LDR and excitation frequencies can be observed in frequency plots. LDR frequencies can be easily detected from bicoherence plots, while its detection from frequency plots is found to be cumbersome. The efficacy of bicoherence analysis in detection of LDR frequency is shown using an aluminium plate with flat bottom hole and three delaminated glass fibre reinforced composite (GFRP) plates. Second harmonic of LDR frequencies are evaluated from the bicoherence plots which can be used later for defect imaging.

To achieve 2 MA plasma current with 300 s pulse length in the Korea Superconducting Tokamak Advanced Research (KSTAR), its pulsed electric power network (PEPN) was designed. The PEPN system, which was installed in 2012, consists of an exciter, a synchronous machine (SM), and a large power variable voltage and variable frequency (VVVF) inverter. Several commissioning activities were performed on the mechanical parts of SM, and the PEPN has been used to supply AC power to the KSTAR superconducting magnet power supplies (MPSs) since entering into service in 2015. However, due to electrical faults in the VVVF inverter during certain types of plasma operations, the operation window of KSTAR has decreased, especially during high plasma current and long-pulse operations. The operation results of the KSTAR PEPN are reviewed in this paper. In addition, a comprehensive study of faults in the VVVF inverter system is performed from the viewpoint of active power variation using real plasma operational scenario results and model-based simulations. This paper also describes the design upgrade of the PEPN system for extended KSTAR operations in the future.

A new fundamental parameter model and calculation algorithm is presented for quantitative analysis for total reflection X-ray fluorescence analytical technique. The model takes into consideration the geometrical parameters of the measuring set-up, the energy distribution of the exciter X-ray beam and its incidence angle to the surface of the sample holder. The numerical solution of this new model results the concentration of the sample elements. The system of equations of the fundamental parameter model involves the mathematical description of the excitation process in the sample layer and in the sample holder. The theoretical calibration for the quantitative determination of the sample elements is based on the numerical comparison of the measured and calculated X-ray fluorescence signal of the pure silicon sample holder. For the numerical calculation computer code was created in order to solve numerically the model equations. The whole analytical procedure is a standard-free method. The theoretical model and the complete numerical calculation was tested experimentally with standard solutions of K, Sc, V, Mn, Co, Ni and Cu elements, which were dripped onto high purity silicon wafer and dried before measurement. This standard-free analytical procedure can be utilized in the semiconductor industry and in various total reflection X-ray fluorescence analysis performed for investigations of environmental samples, natural waters, geological substances, foods and drinks.

The shock resistance of multi-body structure in confined fluid is a hot topic in recent years because of widely using in nuclear reactors, evaporator and so on. The added mass coefficient of elastic rods which is influenced by many factors is one of key parameters in the research of shock resistance. So the added mass coefficient of elastic rods in confined fluid is deduced based on potential flow theory and validated by an experiment. Taylor expansion and coordinate transformation are used in theoretical derivation. In the experiment, rods are stimulated by exciter and impactor and the results show that the added mass coefficient is related to the distance between rod and the boundary, distance between two rods, vibration phase, vibration direction, modes and the number of rods. There is no obvious difference between vibration and impact. Finally, the conclusion can be used in rapid engineering design of similar structure.

Modal analysis in operational conditions is popular way for obtaining natural modes of civil structures such as bridges or dams nowadays. This approach called Operational Modal Analysis (OMA) overcomes difficulties with input forces used for excitation of the structure in Experimental Modal Analysis (EMA). In OMA the input forces are assumed to be stochastic. The paper presents the experimental measurement and analysis of the mode shapes and frequencies of the laboratory steel truss structure using output-only method based on Frequency Domain Decomposition (FDD). FDD technique for a decomposition of the spectral density function matrix in combination with a method for merging measured data from multiple measurement set-ups are both implemented into a data processing tool designed in LabVIEW. Modal exciter and random impulses in random points are used for the structure excitation. The results demonstrate the influence of different types of operational loading on identified modes.

In this paper, an Artificial Neural Network (ANN) based Rotor Oscillations Compensator (ROC) is proposed and its equivalent Hardware Realizable Neural Network (HARNN) has been developed on the Field Programmable Gate Array (FPGA) board. The basic function of a ROC is to minimize the low frequency electro mechanical oscillations created in the Electric power network. Whenever the fault is occurred outside the operating range of a fixed gain ROC, the system damping is insufficient and the machine is still under unstable mode. Hence a hardware having sufficient “intelligence” that is capable of producing necessary and sufficient damping to the system is proposed in this paper. A detailed study has been done with the plant response without any controller, with a fixed gain controller and a FPGA based ANN controller. The studies revealed that when an intelligent controller has been included in the Exciter loop, the oscillations have been eliminated more effectively. But it is also observed that the realization of an ANN absolutely on an FPGA is having its own design limitations. The ARTIX 7 FPGA development board has been used for the complete analysis and the results and outcomes discussed at the end.

A strongly nonlinear system often has multiple solutions under harmonic excitation. However, measuring all of these multiple responses in structural dynamics is challenging because often one solution is unstable and difficult to obtain. The standard stepped sine approach is to fix the harmonic excitation force amplitude, and step the excitation frequency up or down. This leads to the well-known jump phenomenon, and captures at most two stable solutions. Alternatively, the excitation frequency can be fixed and the amplitude swept up or down, although this also leads to jumps in the response. Recently, experimental continuation methods have successfully measured all solutions, including the unstable solutions, via active control. This paper takes a different approach and exploits the dynamics of the electromagnetic exciter to both stabilize the unstable solution, and also to track the solutions continuously, without any jumps. This is achieved by monotonically increasing or decreasing the voltage applied to the exciter at a fixed frequency, and using the force drop-out phenomenon through the resonance to control the force applied to the structure. In these tests, the input voltage then defines the continuation parameter, rather than force amplitude or frequency in the standard tests. The obvious advantage of this method is that there is no feedback control of the excitation and it is easy to implement. A strongly nonlinear single degree of freedom system is used to demonstrate this method.

In the last few years, increasing attention has been given to obtaining reliable results in system identification as a key step in performing model updating, damage detection and structural health monitoring. Many methods have been developed to measure the uncertainty in modal estimates. Some techniques are based on signal resampling to obtain a larger sample space and consequently better process statistics. Thus, this study proposes a new method to quantify uncertainties using the stochastic subspace identification (SSI) technique combined with bootstrap resampling. To validate and compare the performance of the proposed algorithm, two algorithms previously mentioned in the literature were implemented. The first is based on the “moving block method”, and the second is based on blocks of the projection matrix. The proposed method initially generates random decrement functions from signal segments and later uses these functions as bootstrap resampling blocks in SSI. To validate and compare the performance of the proposed algorithm, numerical simulations and two experimental analyses are performed. The first analysis involves a simply supported steel beam subjected to vibration tests through random impacts, and the second involves a three-dimensional four-story frame subjected to vibrations from random signals generated by an electrodynamic exciter. The results of the proposed technique were more robust and accurate than those of the other methods.

Drag type Savonius Vertical Axis Wind Turbine (VAWT) has the advantages of the low total cost, simple manufacture and maintenance. Although the efficiency is low, it is suitable for residential areas with low wind speed. This article intends to use flow control methods to improve the efficiency of Savonius VAWT. Plasma excitation flow control is a relatively new type of active flow control technology. Therefore, this article uses the User-Defined Function (UDF) in ANSYS Fluent to load the plasma excitation sources on the Savonius VAWT blades. This paper numerically studies the influence of plasma flow control on the aerodynamic performance of a two-blade Savonius VAWT. Firstly, the changes in wind turbine performance under different excitation parameters are analyzed. The research results show that adding plasma exciter at a reasonable position can effectively improve the performance of the wind turbine, and the electric field force distribution in different directions will effect its range of action. Meanwhile, the voltage excitation frequency is also an influencing factor. Secondly, the principle and process of plasma excitation on the Savonius VAWT are analyzed. Finally, the relationship between the power consumed by the plasma and the increased power to drive the wind turbine is analyzed. Besides, the influence of plasma excitation on the overall performance of the wind turbine is summarized.

Resonance frequency is a key factor for improving transfer efficiency in a Wireless Power Transfer (WPT) system which has a wide application because the wired media is eliminated. In this paper, an adaptive frequency measurement method is presented and the influence on the transfer efficiency in the WPT system is explored. The LC circuit is adaptively excited by a pulse exciter to generate damped oscillation. The frequency signal of LC circuit is shaped to a rectangle pulse before measurement. In the proposed digital frequency measurement, a direct pulse counting technique is employed in which the pulse width is computed with the counter pulse. The pulse counting is implemented by a constant time window for reducing measurement error in the resonance frequency signal. The frequency measuring method is demonstrated by an experimental study based on coupled magnetic resonances. The experimental results show that the WPT efficiency and the peak power when driven at real resonant frequency are about 2.1% and 2.3%, respectively, higher than that of theoretical values, which indicated a better performance of resonance frequency measurement.

Passage through and capture into the resonance of a centrifugal exciter with two coaxial unbalances driven by an engine of limited power is investigated using an averaging method for a partially strongly damped system . It is demonstrated that the system dynamics can be reduced on the slow manifold to two first-order differential equations that predict both stationary and transient solutions of the original system. The system shows two different types of solutions corresponding to the capture into the resonance. Their occurrence and existence range are investigated in terms of the dependency of engine parameters.

Studies on key influencing factors (coil’s size and excitation frequency) of eddy current testing (ECT) sensitivity, monotonicity and defect detectability have been carried out for detection of subsurface defects in ferromagnetic and non-ferromagnetic plate materials. A set of ECT finite element models and experiments have been accomplished and the detection performance has been analyzed and compared. The simulation and experiment results have indicated that for ferromagnetic material, the amplitude response of low frequency excitation has lower sensitivity but better monotonicity than high frequency. The phase response of low frequency excitation has higher sensitivity and better monotonicity than high frequency. For the non-ferromagnetic plate material, the lower the excitation frequency is, the smaller the detection sensitivity of the amplitude response is. Outside a defined excitation frequency, the defect monotonicity of the amplitude response reduces. For phase response, the lower the excitation frequency is, the smaller the detection sensitivity and the greater the monotonicity. The coil’s size has a certain extent influence on the detection sensitivity. For ferromagnetic and non-ferromagnetic plate materials, it is effective to enhance the detection sensitivity of amplitude response by increasing the size of the exciter coil and the detector coil within a certain range; and it is effective to enhance the detection sensitivity of phase response by decreasing the size of the detector coil or increasing the size of exciter coil within a certain range.

Brushless wound-rotor synchronous starter-generator (WRSSG) is drawing more and more attentions in aircraft power system applications because of advantages such as high safety and low cost in maintenance. Detailed analysis and optimal start control research for the WRSSG system need an accurate and time-efficient integrated model of WRSSG. Because of the presence of the rotating rectifier, there is a complex nonlinear relationship between electrical variables of the brushless exciter and main generator in WRSSG, which makes the building of the integrated model a very tough work. In this paper, an improved Parametric Average Value Model (PAVM) of the rotating rectifier with coefficients varying with load impedance and load current was proposed, and coefficients of the improved PAVM were obtained from simulations of the detailed joint Voltage-Behind-Reactance (VBR) model of WRSSG. Based on the improved PAVM of the rotating rectifier, an integrated model of the WRSSG with a two-phase brushless exciter was proposed in classic state-variable formulation. Computer studies verified that the proposed integrated model of the WRSSG is sufficiently accurate in simulations of both steady and transient states, and it is very computationally efficient compared with detailed switching models.

This study proposes a mode shape scaling and parameterization scheme for modal identification with known input. Through the derivation of the equations for known input modal identification using the proposed mode shape scaling and parameterization scheme, the study provides insight into the relationship between the identified modal parameters and information required in the forced vibration test. In typical applications of modal identifications, when there is sufficient amount of data, the formulation using the proposed mode shape scaling and parameterization scheme shows that it allows modal parameters to be determined efficiently in a globally identifiable manner. An illustrative example using synthetic data is provided in this study. The findings show that an appropriate mode shape scaling and normalization scheme could reduce the information required in the modal identification procedure for some modal parameters, i.e. natural frequencies, damping ratios and mode shapes. This significantly simplifies the procedure of the forced vibration test, and hence, it can be carried out in a more robust manner.

This paper proposed a handheld fruit harvesting device for improving efficiency and reducing cost. Firstly, a kinetic model of dual driven vibration system was built, which was based on size calculation of eccentric block. Then, structure design of a handheld harvester was carried out on basis of stress analysis. A prototype system was made including clamping head, motor driven exciter, controller and battery backpack. An Arduino based controller was developed to adjust the operation frequency and excitation mode. Furthermore, experiment was conducted with a LabVIEW based program to verify the vibration mode and frequency of developed handheld fruit harvester. Obtained results shown that the dual motor driven harvester could provide sufficient power and adjust the excitation mode with high efficiency. Field experiments are expected to validate the operation efficiency with current handheld harvester.

Transient stability of islands after splitting is significantly affected by fault factors such as fault clearing time, fault location and fault type. Reasonable application of these fault factors obtained by protection information allows operators assess transient stability margin (TSM) for islands in a more accurate and effective fashion. This paper presents a protection information based transient stability margin assessment method for islands after splitting to evaluate the effect of fault factors on their TSM. First, analytical expressions for state vectors of generators and algebraic vectors of network that consider fault factors are derived. On the basic of this, the transient energy function of islands with 4th order synchronous generator model and first order approximation exciter dynamic model is developed to determine energy of islands under different fault factors. The corresponding critical energy of islands is determined by the boundary of stability-region-based controlling UEP (BCU) method. Next, the analytical expressions for TSM of islands are derived, which could quickly determine TSM of islands after splitting and critical splitting time of system using protection information. Finally, An IEEE 68 bus system and a practical power system are carried out to demonstrate the validity and effectiveness of the proposed transient stability margin assessment method.

Transient stability analysis is a traditional yet significant topic in power systems. The switching control schemes of the HVDC converter station after fault bring new challenges to the direct method of transient stability analysis in AC/DC power systems. To apply the direct method to investigate the transient stability of power systems accommodating the switching characteristics of the line commutated converter (LCC) HVDC, continuous piecewise Lyapunov functions are constructed for a whole AC/DC system model including several classical LCC-HVDC control modes, and the continuity of Lyapunov functions is studied and guaranteed in transitions between control modes. Then, the Sum-of-Squares optimization is employed to find the optimal continuous piecewise Lyapunov functions. Finally, the transient stability domain is estimated for a sample system including the main control loops of LCC-HVDC, a three-order generator model, and a one-order exciter model. Tests in MATLAB environment are conducted to demonstrate the feasibility of this method.

Role of round rotor synchronous generator in renewable and sustainable energy is rapidly growing due to growing demand of energy production from the renewable resources. The less wear and tear, high robustness and accessibility to power electronics deployment (for active/reactive power flows from and to the grid) has increased the scope of round rotor synchronous generators across large onshore and offshore wind farms besides in hydro power plants. In many commercial power modeling softwares, like System Simulator for Engineering (PSS/E), it is quite difficult to write, access, test, evaluate and validate the built-in models. Therefore to avoid these problems and help the researchers in evaluating, testing, modifying, expanding and enabling the power equipment models as user written, it is important that the equivalent models are designed in an accessible and comparable design and simulation environment like Simulink. The work presented in this paper therefore addresses these issues and provide researchers the equivalent PSS/e models of generator, its associated governor and exciter designed and modeled in Simulink environment.

Condition-based maintenance of electric generators have been gaining increasing importance due to the electricity demand and the criticality that this equipment represents to electrical power systems. In this context, this paper proposes a methodology and a system for detection and modeling of incipient failures in the components of internal combustion engine-driven generators based on Electrical Signature Analysis (ESA). The proposed methodology enables the detection of incipient faults both in the prime mover and in the coupled synchronous generator, only relying on measurements of the generator stator voltages and currents. The proposed ESA failure patterns are based on defined frequencies and the structural features of the machine, so they can be reproduced in a wide range of engine-generators sets. The main advantages of the proposed system are its low intrusiveness, feasible installation and cost efficiency. A scale model laboratory has been designed to simulate faults in a small diesel generator and apply the ESA methodology to detect these faults and obtain the failure patterns. Experimental results are presented to prove the effectiveness of the proposed methodology. The main results include the findings that exciter generator unbalance induces electrical unbalance components, exciter diode short circuit induces even harmonics, intake valve failure and piston ring failure induce multiples of rotation frequency components, and mechanical misalignment of the engine generator set induces multiples of half order speed frequency components on ESA. Moreover, the proposed prototype is installed at two large in-service internal combustion engine-driven generators and examples of signal analysis are provided.

This paper presents a time-domain method for multi-exciter random environment tests. Traditional random environment test theory has been formulated in the frequency domain, where an important step is taking the inverse of the frequency response function matrices (FRFMs). The accuracy of this inversion tends to be poor, particularly at frequencies near lightly damped resonances. The currently used control algorithms face difficulties in suppressing abnormal spectral lines caused by this inverse problem. In this paper, traditional formulations of the environment test are reformed, and the time-domain method is adopted; this results in a more precise inverse operation in environment tests. To achieve this, reference spectra are converted into time-domain response signals. The finite long driving signals are derived by the state-space method with estimated state vectors. During the process, the inverse of rank-deficient Toeplitz matrices are stabilized with truncated singular value decomposition (TSVD) to suppress all abnormally high-level components in the driving forces; thus, overall, the spectra lines produced by noise within the frequency band are filtered out. A numerical simulation of a single-axis random vibration test of a cantilever beam is conducted using the traditional frequency-domain procedure (FDP) and the proposed time-domain procedure (TDP). The response spectra generated by both procedures are tested by control algorithms, and the result shows that responses generated by the proposed TDP are more easily controlled. The conditions of stability for both the FDP and the TDP are also determined and introduced in the simulation. Moreover, a multi-axis vibration experiment further validates the effectiveness of the TDP.

The paper presents novel method for research on exposure to nonlinear vibration of passenger car suspension as nonlinear dynamical system. Also paper provides a discussion on the results of studies addressing the impact exerted by damping properties of shock absorber on the vibrations being generated. The research was conducted on the car forced to vibration by the exciter machine with changeable frequency. The paper addresses results of analysis of application of one of the time-frequency representation techniques to the identification of structure of vibration. The obtained representation of the vibration allows determining time function of separate frequency bands, which represents the isolated vibration dynamics phenomena. Considering the variability of the time and frequency distribution of the vibration even in selected analysed bands, the time function was developed as exposure to vibration estimator. The recommended method makes use of function of exposure to vibration. The advantage of these method is possibilities of precise analysis of chosen frequency bands. The investigations conducted confirm considerable susceptibility to changes in the technical condition of shock absorber with regard to the assessment of human exposure to vibrations.

This study aims to analyze the failure mechanism and improve the structural design of a vibration-based energy harvester (VEH), which intends to replace or extend the service life of batteries for condition monitoring systems of high-risk structures such as railroad vehicles and wind turbines. The observation of a fractured VEH under service condition of high-speed railway vehicle reveals several cracks originating on the surface of the VEH. A vibration test in the laboratory, conducted by using an electromagnetic exciter, identifies the resonant frequency, displacement-frequency, and acceleration-frequency plots of the VEH. A comparison of the surface fractured during vibration testing with that under service condition indicates that the major failure mechanism is static brittle fracture. The failure critical location and stress states are identified through frequency response analysis. Several measures are recommended to prevent the failure of VEHs, including selecting materials and redesigning the moving component of VEH.

In operation, expansion, complication and modernization of electrical power systems one of the important task is stability provisioning. Automatic exciter controller (AEC) functioning in synchronous machine (SM), is one of the devices, allowing to perform this task. The article defines and illustrates the variety of tasks that is necessary to solve by the development of AEC algorithms, analysis of functioning and setting their parameters. New techniques, designed for solution of these tasks are presented. These techniques allow when setting the regulators: 1. Take into account the working conditions of SM. 2. Determine the region of stability for given sets of AEC channel coefficients. 3. Determine the optimal AEC parameters settings, providing the best damping of transient processes under various disturbances. 4. Visually present regulation setting results. Solutions of all the tasks are demonstrated by the example of the analysis of the functioning and the setting up DECS-400 controller operating in a test scheme, assembled with real-time simulator RTDS.

A wavelet network-based nonlinear excitation control is designed to enhance the transient stability of a power system. The power system model used to improve the transient stability via excitation control can be written in the canonical form. The resulting excitation control signal that achieves a prescribed tracking performance is shown to include unknown nonlinear terms. A wavelet network is constructed to generate an approximation of these nonlinear terms and hence facilitate the design of the nonlinear excitation controller. Based on the wavelet network approximation, suitable adaptive control and appropriate parameter update algorithm are developed to force the nonlinear uncertain power system to track a prescribed trajectory with desired dynamic performance. It is shown that the proposed controller achieves ultimately bounded tracking error and boundedness of the closed loop signals. A single machine infinite bus system with uncertain fault location is presented to illustrate the proposed design procedure and exhibit its performance. The performance of the proposed excitation controller is compared with the classical IEEE-type ST1A static exciter equipped with a power system stabilizer. The paper addresses the problem of designing a wavelet network-based nonlinear excitation control for power systems. A wavelet network is utilized in designing such controller.The capability of a wavelet network to approximate nonlinear functions is exploited in this work. The objective of the proposed adaptive wavelet controller is to achieve tracking between the power system output (generator angle in this case) and a prescribed reference trajectory.This controller achieves ultimately bounded tracking error and boundedness of the closed loop signalsThe proposed controller is compared with the classical IEEE static exciter.The comparison proves the effectiveness of the proposed controller in damping out power system oscillations that occur due to sever abnormality (e.g. three-phase to ground fault).

Rotor blades are among the most delicate components of modern wind turbines. Reliability is a crucial aspect, since blades shall ideally remain free of failure under ultra-high cycle loading conditions throughout their designated lifetime of 20–25 years. Full-scale blade tests are the most accurate means to experimentally simulate damage evolution under operating conditions, and are therefore used to demonstrate that a blade type fulfils the reliability requirements to an acceptable degree of confidence. The state-of-the-art testing method for rotor blades in industry is based on resonance excitation where typically a rotating mass excites the blade close to its first natural frequency. During operation the blade response due to external forcing is governed by a weighted combination of its eigenmodes. Current test methodologies which only utilise the lowest eigenfrequency induce a fictitious damage where additional tuning masses are required to recover the desired damage distribution. Even with the commonly adopted amplitude upscaling technique fatigue tests remain a time-consuming and costly endeavour. The application of tuning masses increases the complexity of the problem by lowering the natural frequency of the blade and therefore increasing the testing time. The novel method presented in this paper aims at shortening the duration of the state-of-the-art fatigue testing method by simultaneously exciting the blade with a combination of two or more eigenfrequencies. Taking advantage of the different shapes of the excited eigenmodes, the actual spatial damage distribution can be more realistically simulated in the tests by tuning the excitation force amplitudes rather than adding tuning masses. This implies that in portions of the blade the lowest mode is governing the damage whereas in others higher modes contribute more significantly due to their higher cycle count. A numerical feasibility study based on a publicly available large utility rotor blade is used to demonstrate the ability of the proposed approach to outperform the state-of-the-art testing method without compromising fatigue test requirements. It will be shown that the novel method shortens the testing time and renders the damage evolution with a higher degree of fidelity.

Diesel-Engine Driven Generators (DDGs) are a kind of distributed generation (DG) units and similar to other DGs, cause power quality disturbances in power system. Flicker is one of the most important power quality disturbances having bad effects on the sensitive loads. In DDGs, Inherent Torque Fluctuations (ITFs), Misfiring (MF) in various cylinders, Gearbox Tooth Crashing (GTC), governor and exciter errors in presence of the mentioned factors are some of the faults, which produce flicker. Therefore, it is necessary to recognize any faults causing flicker to prevent serious problem in DDGs. Also, identifying these factors is effective in accelerating process of repair and maintenance for DDGs. Therefore, in this paper firstly, all faults that cause flicker are modeled and simulated, then a pattern recognition method is presented for their detection. In the proposed method, Discrete Wavelet Transform (DWT) and Discrete S-Transform (DST) are used for feature extraction and Gram-Schmidt (GS) is used for feature selection. Afterwards, a classifier based on K-Nearest Neighbors (KNN) is used to detect the faults. Also, the impact of faults on flicker severity has been evaluated by short-term severity of flicker (Pst index).

In this paper a prototype clamped free beam novel energy harvester (NEH) was designed and demonstrated in detail by using CATIA V5 tool. And also it was tested on 20g electromagnetic exciter at different striking loads and under the frequency of 60 Hz by using lead zirconate titanate (PZT-5H) discs or patches or transducers or circular diaphragms. The recorded output power is 5.264 mW at 0.49 N load. 5.264 mW output power can be used for operating the low power devices such MEMS devices and electronic microprocessors.

A design of the exciter of weather fax chart and NAVTEX is described in this paper, which has the advantages of miniaturization, low power consumption, high reliability. The exciter is made up of hardware equipment and PC client. The hardware principle and the working process of PC client are listed respectively. Finally, a receiving and launching experiment is used to verify the validity of the exciter's function; moreover, the power and volume of the exciter are given to support its advantage.

With the increasing demand for the cleaner production of electric energy, many countries around the world strive to develop new turbo-generators with advanced parameters and large capacities. In the design of a new turbo-generator, it is important to optimize the anti-vibration performance of its key components in order to ensure its safe and reliable operation. The anti-vibration optimization of the key components in a turbo-generator when a set of alternative schemes are provided for selection is a heterogeneous multi-attribute decision making (HMADM) problem involving deviation attributes, which cannot be solved by present HMADM approaches. To solve such a HMADM problem, a novel heterogeneous axiomatic design (HAD) method is developed by introducing the distance measure into axiomatic design for computing the information contents of the alternative schemes. With the attribute data in various mathematical forms unified as triangular fuzzy numbers, their probabilities of success can be conveniently calculated by a unified formula once their corresponding positive and negative ideal solutions are determined. As a result, the complexity and computational cost involved in computing the information contents of alternatives can be greatly reduced, which enables the efficient solution of the HMADM problem involving deviation attributes. A case study on the fixture scheme optimization for the stator end windings in a large turbo generator demonstrated the feasibility and effectiveness of proposed HAD. The ninth fixture scheme with the structural manufacturability being very good (VG), the natural frequencies at the turbine and exciter ends being [68.2, 78.5]Hz and [72.5, 83.2]Hz, the maximum amplitudes at the turbine and exciter ends being 67 μm and 72 μm was chosen as the optimal scheme from nine alternatives according to the HMADM results.

A novel panel-form loudspeaker in which the panel of the speaker is excited by the forces generated through the flat voice coil of a rectangular electro-magnetic type exciter for sound radiation is presented. The exciter when properly designed has the advantage of exerting appropriate loads to the panel so that the major sound pressure level (SPL) dips of the speaker can be suppressed or even eliminated. For designing such panel-form speaker, a method formulated on the basis of the classical plate theory (CPT), Ritz method, and first Rayleigh integral is proposed for predicting the SPL curve of the speaker. An experimental investigation was performed to verify the feasibility of the proposed method. The effects of some system parameters on the major SPL dips of the proposed panel-form speakers are investigated by means of several numerical examples. The optimal locations of flat voice coils for exciting several panel-form speakers are determined to illustrate the important role of excitation location for enhancing sound quality of such speakers via the removal or suppression of the major SPL dips.

In this paper the double and triple-frequency synchronization of the two co-rotating exciters, in a far super-resonant vibrating system, are analyzed by theory, numeric, simulation and experiment. The motion differential equations of the system are given firstly. The theoretical conditions of implementing double/triple-frequency synchronization, are deduced by introducing the asymptotic method and average method, and the stability conditions for the corresponding synchronous states are verified to satisfy Routh-Hurwitz criterion. Based on the theory results, the stable states of the system are qualitatively discussed in detail by numeric, which is further examined by the following simulations and experiments. It is shown that, the stability of the system is mainly determined by the stability ability coefficient (SAC) depending on a key dimensionless structural parameter (KDSP), and the KDSP is a ratio between the distance from rotational center of each exciter to centroid of the system and its equivalent rotational radius. Under the precondition of the two identical exciters, the phase difference between the two exciters for double/triple-frequency synchronization, is stabilized in the vicinity of zero when SAC is greater than zero; otherwise, it is stabilized in the neighborhood of Pi. The present work can provide a foundation for designing some new types of vibrating machines characterized by two frequencies.

In the current study, an operational modal analysis is performed on a wind turbine blade with pull-and-release excitation at the tip. The experiments were carried out in large-scale facility of Risoe campus in Technical University of Denmark. Two different blade configurations are compared – blade on the block and a configuration for fatigue testing comprising of blade on the block with mass resonance exciter and seismic masses. A continuous wavelet transform is employed for estimation of modal parameters of the fundamental flapwise bending mode of the blade from acceleration responses. Statistical analysis along with an outlier removal from the extracted modal parameters is carried out to provide clear estimates of the extracted values. These results are compared to the values extracted with other algorithms. The proposed method for modal parameter extraction aims at extraction of numerous observations allowing for statistical decision making and machine learning capabilities.

When a hypersonic aircraft flies at a high Mach number, the plate-like attitude control structures, such as the wings and rudders, will be exposed to an extremely high-temperature environment. To obtain the thermal modal parameters of a structure that are difficult to measure, a high-temperature transient heating test system and a vibration test system were combined to establish a test system that can perform the thermal/vibration test at 1200 °C. Infrared radiation heating was employed to generate a controlled time-varying high-temperature environment, and an exciter was used to exert vibration excitation on the free end of the cantilever rectangular plate. A self-developed extension configuration of a high-temperature-resistant ceramic pole was used to transfer the vibration signals of the structure to a non-high temperature zone, and the acceleration sensors were applied to identify the vibration signals. The test data were analyzed using a time-frequency joint analysis technique, and next, the key vibration characteristic parameters of structure in a thermal-vibration coupled environment up to 1200 °C (e.g., the modal frequency and modal vibration shape) were experimentally obtained. In addition, the numerical simulation on the thermal modal characteristics of a rectangular plate was performed. The calculated results coincide favorably with the test results, verifying the credibility and effectiveness of the experimental methods. The research results can provide an important basis for the dynamic performance analysis and safety design of structure under high-temperature thermal-vibration conditions for hypersonic flight vehicles.

In the oil industry, drillstring can be used as a transmission medium to send downhole information via a modulated compressional acoustic wave. However, the accompanied reverberation is a major constraint in the transmission rate and distance because of the multipath fading caused by the heterogeneous drillstring. In combination with discrete Fourier transform-spread (DFT-S) mapping/demapping, high-power amplitude squeezing and DFT-based least squares channel estimation methods, an improved orthogonal frequency division multiplexing (OFDM) scheme is proposed in this paper to overcome the symbol interference inherent in the drillstring multipath channel and reduce the peak-to-average power ratio of the signal. Then an experimental rig is established by using a rotatable electromagnetic vibration exciter and a piezoelectric accelerometer arranged at the position closer to acoustic impedance terminal along a 6.3-m periodic simulated drillstring. The OFDM data sequences at a data rate of 200 bit/s over a limited bandwidth of 140 Hz are applied to the rotating simulated drillstring. The experimental results show that the proposed scheme using QPSK modulation can offer an error-free acoustic communication at rotation speeds up to 90 r/min.

The development of an effective high-temperature superconducting (HTS) generator is currently a research focus; however, the reduction of heat loss of a large-scale HTS generator is a challenge. This study deals with a heat loss analysis-based design of a 12 MW wind power generator module having an HTS flux pump exciter. The generator module consists of an HTS rotor of the generator and an HTS flux pump exciter. The specifications of the module were described, and the detailed configuration of the module was illustrated. For the heat loss analysis of the module, the excitation loss of the flux pump exciter, eddy current loss of all of the structures in the module, radiation loss, and conduction loss of an HTS coil supporter were assessed using a 3D finite elements method program. In the case of the conduction loss, different types of the supporters were compared to find out the supporter of the lowest conduction loss in the module. The heat loss analysis results of the module were reflected in the design of the generator module and discussed in detail. The results will be applied to the design of large-scale superconducting generators for wind turbines including a cooling system.

This work proposes the generalization of models for excitation systems. Thirteen models according to IEEE standard are reduced to three main types by the development of a common universal excitation control model. The original IEEE division of exciter types into alternator-supplied rectifier and static excitation system is rearranged into non-controlled and controlled rectifier types. This division is suitable for model classification and for authors and users of network simulators. Proposed simplification may facilitate a data collection of dynamic models for studies of large power system.

Performance of repetitively pulsed xenon chloride excimer laser (λ~308 nm) with solid state pulser consisting of magnetic pulse compression circuit (MPC) using all ferrite magnetic cores (AFMC) is reported. Laser system suitable for 100 Hz operation with inbuilt pre-ionizer, compact gas circulation and cooling has been developed and presented. In this configuration, high voltage pulses of ~8 µs duration are compressed to ~100 ns by magnetic pulse compression circuit with overall compression factor of ~80. Pulse energy of ~18 J stored in the primary capacitor is transferred to the laser head with an efficiency of ~85% compared to ~70% that is normally achieved in such configurations using annealed met-glass core. This is a significant improvement of about 21%. Maximum output laser pulse energy of ~100 mJ was achieved at repetition rate of 100 Hz with a typical pulse to pulse energy stability of ±5% and laser pulse energy of 150 mJ was generated at low rep-rate of ~40 Hz. This exciter uses a low current and low voltage solid state switch (SCR) that replaces high voltage and high current switch i. e, thyratron completely. The use of solid state exciter in turn reduces electromagnetic interference (EMI) effects particularly in excimer lasers where high EMI is present due to high di/dt. The laser is focused on a thin copper sheet for generation of micro-hole and the SEM image of the generated micro hole shows the energy stability of the laser at high repetition rate operation. Nearly homogeneous, regular and well developed xenon chloride (XeCl) laser beam spot was achieved using the laser.

Flow-induced vibration of a harmonically actuated flexible plate in the wake of an upstream bluff body is experimentally investigated. The experiments are performed in an open-ended wind tunnel. A flexible plate trailing a bluff body is under fluid induced excitation due to the flowing fluid. The additional external excitation to the trailing plate is applied using an electro-magnetic exciter. The frequency and amplitude of the external harmonic excitation are selected as variable parameters in the experiments and their effect on the plate vibration and is investigated. To know the nature of acoustic pressure wave generated from the vibrating system, near-field acoustic pressure is also measured. A laser vibrometer, a pressure microphone and a high-speed camera are employed to measure the plate vibration, pressure signal, and instantaneous images of the plate motion respectively. The results obtained indicate that the dynamics of the plate is influenced by both the flow-induced excitation and external harmonic excitation. When frequency of the two excitations is close enough, a large vibration level and a high tonal sound pressure are observed. At higher amplitude of external excitation, the frequency component corresponding to the flow-induced excitation is found to reduce significantly in the frequency spectrum of the vibration signal. It is observed that, for certain range of excitation frequency, the plate vibration first reduces, reaches a minimum value and then increases with increase in the level of external excitation. A fair qualitative agreement of the experimental results with numerical simulation result of the past study has been noted. In addition to the experiments, the role of phase difference between the flow-induced excitation generated from the front obstacle and externally applied harmonic excitation is investigated through numerical simulations. The result obtained reveals that the final steady state vibration of the coupled system is independent of the initial phase difference between the two excitations.

The active health monitoring of rotordynamic systems in the presence of bearing outer race defect is considered in this paper. The shaft is assumed to be supported by conventional mechanical bearings and an active magnetic bearing (AMB) is used in the mid of the shaft location as an exciter to apply electromagnetic force to the system. We investigate a nonlinear bearing-pedestal system model with the outer race defect under the electromagnetic force. The nonlinear differential equations are integrated using the fourth-order Runge-Kutta algorithm. The simulation and experimental results show that the characteristic signal of outer race incipient defect is significantly amplified under the electromagnetic force through the AMBs, which is helpful to improve the diagnosis accuracy of rolling element bearing׳s incipient outer race defect.

Machine tools are the main driving forces of industrialization of a country. However, poor machinability because of chatter vibration results in poor surface quality, excessive noise, and reduced material removal rate. Modal testing is a useful method to investigate dynamic properties of a cutting tool system and improve material removal rate. However, at present, modal testing using impact hammer is limited by certain problems. This paper developed a non-contacting electromagnetic actuator (EMA) to determine frequency response functions (FRFs) under amplitude and speed dependencies of cutting milling tools. The geometry was designed using magnetic circuit analysis and generalized machined theory before finite element analysis was conducted using magnetostatic-ansys software. Next, EMA was used as a contacting and non-contacting exciter of a conventional milling machine to determine the FRFs and dynamic properties of milling tool with amplitude and speed dependencies including comparison with static FRFs. Subsequently, dynamic properties and FRFs are used to establish stability lobe diagram. Stability lobe diagram also shows an improvement of up to 5% of depth of cut at lower spindle speed. In conclusion, by generating force that applies to static and dynamic modal testing, an EMA can determine dynamic properties and stability lobe diagram for increasing material removal rate and production rate.

Conventional electro-hydraulic excitation is usually controlled by a servo valve employing a sliding spool type construction. However, the comparatively slow response of the servo valve will greatly limit the system's high-frequency performance. Therefore, a rotary valve with the rotary motion of the spool as a new excitation mechanism is proposed to obtain the desired excitation, especially a high-frequency excitation wave for fatigue. An electro-hydraulic exciter using a combination of a three-way two-dimensional rotary valve (2D rotary valve) and an unequal area piston is taken as an example. Analysis of the vibration output to a typical wave input yields an analytic solution of the vibration waveform excited by this electro-hydraulic system. The mathematical formulation of the harmonics is also derived. Additionally, an electro-hydraulic excitation test-bed is built to acquire an experimental excitation wave. Consequently, the analysis of the excitation waveform in an approximate analytical and experimental method is used to verify access to high-frequency excitation, even resonance excitation.

In this paper the effect of heat on the performance of novel energy harvester (NEH) by using PZT-5H circular transducers was mentioned. PZT-5H circular transducers were heated at three different temperatures such as 20 0 C, 60 0 C and 100 0 C and tested on 20 g exciter under sinusoidal support excitation by using NEH. The observations were made on three parameters: temperature effect on impedance, temperature effect on resonant frequencies and temperature effect on the output voltage. At 20 0 C, the output voltage is 23 V and at 100 0 C the output voltage is 18 V is recorded. The observation is that the temperature effects the performance of PZT-5H circular transducers.

This paper deals with an active structural acoustic control approach to reduce the transmission of tonal noise in aircraft cabins. The focus is on the practical implementation of the virtual mechanical impedances method by using sensoriactuators instead of conventional control units composed of separate sensors and actuators. The experimental setup includes two sensoriactuators developed from the electrodynamic inertial exciter and distributed over an aircraft trim panel which is subject to a time-harmonic diffuse sound field. The target mechanical impedances are first defined by solving a linear optimization problem from sound power measurements before being applied to the test panel using a complex envelope controller. Measured data are compared to results obtained with sensor–actuator pairs consisting of an accelerometer and an inertial exciter, particularly as regards sound power reduction. It is shown that the two types of control unit provide similar performance, and that here virtual impedance control stands apart from conventional active damping. In particular, it is clear from this study that extra vibrational energy must be provided by the actuators for optimal sound power reduction, mainly due to the high structural damping in the aircraft trim panel. Concluding remarks on the benefits of using these electrodynamic sensoriactuators to control tonal disturbances are also provided.