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This article investigates the joint effects of connection weight and time delay on pattern formation for a delayed reaction-diffusion BAM neural network (RDBAMNN) with Neumann boundary conditions by using the (k₁,k₂) mode Hopf-zero bifurcation. First, the conditions for k₁ mode zero bifurcation are obtained by choosing connection weight as the bifurcation parameter. It is found that the connection weight has a great impact on the properties of steady state. With connection weight increasing, the homogeneous steady state becomes inhomogeneous, which means that the connection weight can affect the spatial stability of steady state. Then, the specified conditions for the k₂ mode Hopf bifurcation and the (k₁,k₂) mode Hopf-zero bifurcation are established. By using the center manifold, the third-order normal form of the Hopf-zero bifurcation is obtained. Through the analysis of the normal form, the bifurcation diagrams on two parameters' planes (connection weight and time delay) are obtained, which contains six areas. Some interesting spatial patterns are found in these areas: a homogeneous periodic solution, a homogeneous steady state, two inhomogeneous steady state, and two inhomogeneous periodic solutions.

In this paper, a fault-tolerant model-free predictive controller (FT-MFPC) for cascaded H-bridge multilevel inverters (CHMLIs) is proposed. FT-MFPC is based on an association of model-free predictive controller (MFPC) and a PI-like structure known as current variation controller (CVC). As in MFPC, the dynamic structure (DS) which is used for prediction of the system output is obtained from past measurements of current variations, but CVC modifies the dynamics before they are stored for prediction. As a consequence, even if the converter operates with bypassed modules, FT-MFPC adapts its DS to represent the real dynamics of the system and enables a closed-loop response with balanced load currents in unbalanced CHMLIs. Simulation and experimental results validate the adaptability of the proposed strategy to operate a seven-level inverter under various configurations of bypassed H-bridge modules. The experimental results show that, for different post-fault operations, the maximal current THD and imbalance factor at steady state in the worst-case scenario are below 5% and 2%, respectively.

The drive to miniaturize power electronics motivates investigation into alternative passive component technologies such as piezoelectrics, which offer fundamentally higher power density and efficiency capabilities at small scales compared to magnetics. Piezoelectric transformers (PTs) have seen application in dc-dc converters, but these designs typically require additional magnetics for competitive efficiency. In this work, we systematically enumerate isolated and non-isolated dc-dc converter topologies and switching sequences capable of efficiently utilizing PTs as their only energy storage components. The proposed switching sequences maintain high-efficiency behaviors (e.g., zero voltage switching (ZVS), all-positive instantaneous power transfer, and minimal charge circulation) across wide voltage gain and load ranges. We present techniques for deriving these switching sequences’ ZVS regions, estimating PT efficiency, and solving for periodic steady state switching times; these offer insights for comparing and implementing design options. We then verify our analyses in a 180-500 V experimental prototype based on a commercially-available PT, which demonstrates significant efficiency gain through a proposed implementation.

The hysteresis of the piezoelectric actuator (PEA) exhibits obvious rate dependence, especially in fast scanning or tracking. This paper proposes an adaptive hysteresis compensation method that integrates the direct inverse modeling (DIM) method and an adaptive Kalman filter (AKF). DIM is adopted to directly obtain the inverse hysteresis model and use it as the hysteresis compensator. AKF is utilized to dynamically update the weights of the inverse hysteresis model so as to eliminate the manual tuning of control parameters. Further, a forgetting factor is adopted in AKF to reduce the influence of the old data. Experimental results on tracking of step, sinusoidal and triangular trajectories demonstrate the effectiveness of DIM+AKF in hysteresis compensation. The transient and steady state performances of the closed-loop system are significantly improved. A closed-loop bandwidth higher than 200 Hz is achieved. The robustness of DIM+AKF against the rate dependence is further verified using a 0-200 Hz swept sinusoidal trajectory. As the on-site tuning is successfully eliminated, DIM+AKF is easy to follow for experienced users.

The integration of dc power distributed systems in modern shipboard microgrids is receiving much attention recently due to their high efficiency and grid connection flexibility. These dc shipboard microgrids (dc-SMGs) are characterized by having different operating modes and large proportion of electric propulsion, some of which involves severe dynamic/transient conditions. Considering various operation modes of actual ships, this paper proposes a hierarchical coordinated control, which includes primary control level (PCL) and power management system (PMS) for the coordinated operation of the power sources in dc-SMGs. The coordination between the PCL and the PMS provides the following features: First, the PCL includes primary speed regulation (PSR) of diesel generator (DG) and primary voltage control (PVC) of dc bus. The PVC can realize the dynamic/steady load power sharing by adding the virtual impedance loop, and the PSR of DG performs the rotation speed to follow the reference. Second, the PMS includes optimal speed reference setting and secondary voltage recovery control that can realize variable-speed operation of DG according to its optimal energy efficiency characteristic and improve the power quality. The simulation results are carried out under MATLAB/Simulink to verify the effectiveness and robustness of the proposed control.

Due to the high resistance/reactance (R/X) ratio of a low-voltage microgrid (LVMG), virtual complex impedance-based P-· V/Q-ω droop control is adopted in this article as the primary control (PC) technique for stabilizing the system. A distributed event-triggered restoration mechanism (ETSM) is proposed as the secondary control (SC) technique to restore the output-voltage frequency and improve power sharing accuracy. The proposed ETSM ensures that neighboring communication happens only at some discrete instants when a predefined event-triggering condition (ETC) is fulfilled. In general, the design of the ETC is the crucial challenge of an event-triggered mechanism (ETM). Thus, in this article, a static ETM (SETM) is proposed as the ETC at first, where two static parameters are utilized to reduce the triggering frequency. Bounded stability is ensured under the SETM, which means that the output-voltage frequency is restored to the vicinity of its nominal value, and close to fair utilization of the distributed generators (DGs) is achieved. To further improve the power sharing accuracy and accelerate the regulation process, a dynamic ETM (DETM) is then introduced. In the DETM, two dynamic parameters that converge to zero in the steady state are designed, which promises asymptotic stability of the system. Besides, Zeno behavior is excluded in both mechanisms. An LVMG consisting of four DGs is constructed in MATLAB/Simulink to illustrate the effectiveness of the proposed methods, and the simulations correspond with our theoretical analysis.

In this work, we present a novel consensus-based secondary control scheme for current sharing and voltage balancing in DC microgrids, composed of distributed generation units, dynamic RLC lines, and nonlinear ZIE (constant impedance, constant current, and exponential) loads. Situated atop a primary voltage control layer, our secondary controllers have a distributed structure, and utilize information exchanged over a communication network to compute necessary control actions. Besides showing that the desired objectives are always attained in steady state, we deduce sufficient conditions for the existence and uniqueness of an equilibrium point for constant power loads -- E loads with zero exponent. Our control design hinges only on the local parameters of the generation units, facilitating plug-and-play operations. We provide a voltage stability analysis, and illustrate the performance and robustness of our designs via simulations. All results hold for arbitrary, albeit connected, microgrid and communication network topologies., Comment: arXiv admin note: substantial text overlap with arXiv:2005.00068

In the analysis and design of a network system, one is often faced with the situation where the network structure is known but the node dynamics is almost unknown. Thus structural analysis problems, in which the prior knowledge is almost about the network structure, have received attention in science and engineering fields. Along this line of research, this paper addresses a structural design problem, that is, to find a sign pattern of the control input such that any constant input with the sign pattern drives the system to a desirable steady state in a qualitative sense. A solution is presented by reducing the problem into a design problem of the so-called sign-solvable equation, which is a linear equation whose qualitative solution can be determined from the prior knowledge of the sign pattern of the coefficients. Our framework is demonstrated by applying to a control problem of the biological network of apoptosis.

It is difficult to obtain linear output displacements for stepping piezoelectric platform due to their discontinuous outputs. Inspired by the theory that the maximum static friction force is greater than the sliding friction force, this letter proposed a bipedal alternating inertial actuation mode (BAIAM) to improve the displacement linearity of stepping platform. The output displacements are measured, the linear fitting is carried out by the least square method, the correlation coefficient and linear fitting function are used to evaluate the displacement linearity, the correlation coefficients of the forward and backward motions are calculated as 0.9998 and 0.9999 in BAIAM, respectively, which verifies the effectiveness of the proposed method. Closed-loop experiments in BAIAM are also carried out, the steady state errors for target position of 40 m within 0.2 m in the point-to-point positioning control experiments are achieved. The experiment results confirm that the developed platform can be applied in precision fields requiring large travel range, planar two-DOF motion and linear outputs.

Pole-phase modulation based multiphase induction motor (PPMIM) drives possess the capability of providing an extended range of speed-torque for high power traction application with the available additional degrees of freedom in the multiphase machine. As observed in previous open-loop results of PPMIM drives presented in the literature, the transient currents often exceed twice the rated currents. To address this issue, this paper focuses on the modelling and advanced control of the PPMIM drives during all possible pole-phase combinations. The dynamic mathematical modelling of the PPMIM in actual phase variable domain is presented in detail. Since this model involves time-dependent inductances and torque, the machine model equations are transformed into dq domain using transformation matrices. The transformation matrices, modelling equations in the arbitrary reference frame and multiphase inverter are modelled by considering all parameters of possible pole-phase combinations. Based on the proposed modelling equations, an indirect field oriented control (IFOC) is implemented for PPMIM drives for smoother operation in all possible modes of operation. The modelling equations, as well as IFOC of PPMIM drive, are implemented in MATLAB to illustrate the behaviour of machine during transients as well as different load torques. The proposed concepts are also validated on laboratory setup and the hardware results are demonstrating the smoother transition as well as steady state operation of PPMIM drive in pole changeovers as well as both pole-phase combinations.

Hybrid energy storage microgrid represents the future direction of distributed energy development. However, under the influence of interference, the dynamic performance of the output side interface will be severely deteriorated. In this paper, a linear active disturbance rejection controller with reference differential feedforward and cascade extended state observer (ADRC-RDCO) is proposed to deal with unknown modeling error and the unknown dynamics of the interface converter. In this strategy, a cascaded linear extended state observer (CLESO) is introduced to cope with the steady state offset in the disturbance estimation error, so as to implement the accurate reconstruction of the disturbance state. Furthermore, a control law with reference differential feedforward (RDF) is applied to offset a portion of the tracking error of the given signal to achieve the purpose of optimizing the tracking accuracy of the given signal. Then, the tracking performance and stability of ADRC-RDCO are analyzed theoretically. On the basis of discussing the relationship between dynamic characteristics and control parameters, a parameter configuration method is proposed. Finally, the proposed ADRC-RDCO technology was verified on the 40 kW microgrid platform.

This paper proposes a torque ripple reduction method based on speed ripples for PMSM drives. The torque ripples are first estimated based on speed harmonics at low speed. Based on that, the optimal harmonic current reference is then derived to fully compensate the estimated torque ripple with minimum stator resistive loss. An extended state observer (ESO) based deadbeat harmonic current controller (DHCC) is also presented in the rotor reference frame (RRF) to inject the optimal harmonic currents with good performance in steady state and transients. To extract the harmonic currents for harmonic current control and speed harmonics for torque ripple estimation with fast convergence and good accuracy, an adaptive linear neural (ADALINE) network-based filter is implemented in this paper. Simulations and experiments are carried out to show the validity and performance of the proposed torque ripple reduction method.

For AC microgrids with three-phase unbalanced loading conditions, the four-wire voltage source inverters (FWVSIs) have become an advisable interfaced converter between the source and loads. Predictive control has been applied to FWVSIs in recent years, but model errors are not solved well, which is caused through parameter mismatch, sampling error and time delay. Thus, the accurate following between reference value and predicted value is difficult to achieve. To this end, a dual-predictive control based on adaptive error correction (DPCEC) for the FW-VSIs is presented. Firstly, the state-space function of FW-VSIs under reference frame is built. Then, the DPCEC strategy is proposed based on the above issue. Therein, an adaptive error correction strategy is severally embedded into both the outer and inner prediction loop. Noting that the impacts of different negative factors can be simultaneously processed and corrected through adaptive error correction strategy. Not only does the proposed control strategy achieve better performance in steady state, but also retains fast dynamic response in transient state. Finally, simulation and experimental results which verify the high performance of the proposed control techniques are provided.

As a new type of flux modulation machine, line-start permanent magnet vernier machine (LSPMVM) has drawn more and more attention. Thanks to the rotor starting winding, the self-starting capability of which can be acquired without applying the inverters. As a result, the system reliability has been improved and cost can be decreased, which is promising for industrial applications, such as pumps and fans. In order to extend the family of LSPMVMs and select the preferable topologies meeting the different requirements, four LSPMVMs, including V-shaped LSPMVM, consequent-pole U-shaped LSPMVM, dual-stator spoke LSPMVM and consequent-pole surface-mounted permanent magnet (SPM) LSPMVM, have been proposed in this paper. And the steady state performance, starting and synchronization capability are comprehensively analyzed and compared, where the regular commercial line-start permanent magnet synchronous machine (LSPMSM) is used as a counterpart. It is found that all the proposed LSPMVMs can acquire the higher torque density. Especially, the V-shaped LSPMVM and consequent-pole U-shaped LSPMVM have the highest torque density, while the consequent-pole SPM LSPMVM can be a better candidate where the low cost is desirable. Finally, the prototype of V-shaped LSPMVM has been manufactured, where experimental results match well with finite element analysis (FEA).

Finite control set model predictive control (FCS-MPC) has been widely recognized in the field of electrical drive control during the past decades, due to its merits of quick dynamic response and low switching frequency. However, it is inherently penalized by the high tracking deviations in the steady state as well as exhaustive search among the switching sequences. To cope with this issue, a low-complexity gradient descent based finite control set predictive current control (GD-FCSPCC) combined with backtracking optimized iteration approach is proposed in this paper, aiming to improve the control performance by effectively tracking the reference value. Firstly, FCS-PCC is reformulated as a quadratic programming (QP) problem from a geometric perspective. Consequently, the convexity of QP problem is proved to underlying the gradient descent to minimize the tracking error in an effective manner. Thus, the control objectives are determined by optimizing the deviation between the gradient descent and the stator current derivative in a cascade structure, to reduce the number of enumerated sequences. The procedures are repeated in the iteration periods optimized via a backtracking search method, until the stopping criterion is satisfied. The effectiveness of the proposed GD-FCSPCC is experimentally validated on a 2.2 kW induction machine testbench.

We incorporate into a standard growth model endogenously determined cultural attributes that complement capital endowments. The resulting propagation mechanism implies that the economy exhibits multiple steady states, convergence to which depends, in particular, on the initial income distribution, featuring persistent income inequality and the lack of income convergence within the economy. An application of the baseline model indicates that the initially disadvantaged ethnic group is overrepresented in the low steady state, and its high steady state income level is lower than that of the initially advantaged group. Initial income redistribution and social integration affect the economy's steady state configuration. These results are interpreted in the light of existing evidence pertaining to such differentials in the US.

On the basis of literature sources analysis, the paper provides the rationale for the necessity of considering the limited digital devices capabilities when designing closed digital control systems for the complex electrical power grids. The problem of design is decomposed into two subproblems: design of current state observation vector digital transmission systems and current controlled process state estimation; design of digital systems for optimal control vector calculation, transmission and control actions realization. The paper presents consideration of the former problem, i.e. design of current state observation vector digital transmission systems and current controlled process state estimation: the mathematical model of digital system of information transmission and state estimation considering speed and reliability of technical means of implementation is presented; the functional structure of simulation complex is developed; the paper provides the formulation of the problem of estimating the optimal amount of information about the control object state, resulting in a solution of computational experiments simulating complex. © 2021 The Author(s). The reported study was funded by RFBR, Russia, Sirius University of Science and Technology, JSC Russian Railways and Educational Fund “Talent and success”, project number 20-38-51007.

Finite Control Set Predictive Current Control (FCS-PCC) is widely recognized as a competitive control strategy in the field of electrical drives, due to its superiority of fast dynamic response and low switching frequency. However, FCS-PCC is penalized by its inherent drawback that the discrete nature of switching states leads to relatively high torque and current deviations. In this paper, an iterative gradient descent method combined with least squares optimized duty cycles is presented to improve the steady-state performance of FCS-PCC. Unlike the cost function optimization in the conventional FCS-PCC, the quadratic programming problem is solved from a geometric perspective, by obtaining the gradient descent which minimizes the tracking deviation in the fastest manner. To synthesize the gradient descent, the optimal stator current derivatives in the current and previous iteration are employed, and their duty cycles are determined by the least squares method. The abovementioned procedures are iteratively repeated in the dichotomy-based periods. The experimental performance of the proposed gradient descent based FCS-PCC is verified at a 8 kHz sampling frequency, which is compared with that of conventional and dichotomy-based FCS-PCC. It is validated that the proposed algorithm outperforms the conventional and dichotomy-based FCS-PCC at both the steady-state and transient state.

In this paper, an efficient model predictive control (MPC) using virtual voltage vectors for three-phase three-level converters is proposed. The proposed MPC achieves constant switching frequency by applying four voltage vectors (VVs), including one virtual VV and three other VVs, in each control cycle. In addition, to reduce the computational burden, two-stage MPC approach is adopted. The first stage chooses one of six medium voltage vectors that minimizes the cost function. Then, in the second stage, these voltage vectors including virtual voltage vectors which locate the same sector with the optimal medium voltage vector, are involved in the MPC optimization. The advantages of the proposed MPC over the classical MPC have been validated through experimental results.

ℒ 1 adaptive control method is a new and effective technique to perform a robust tracking response with fast adaptation, its applications were generalized for both integer order affine and non-affine nonlinear systems. However, ℒ 1 adaptive control scheme has not been yet investigated to control fractional order systems. In this work, an ℒ 1 adaptive controller is designed based on a fractional order sliding surface to control a class of fractional order systems with matched uncertainties and external disturbances. The developed controller is able to achieve closed-loop stability with uniform performance bounds for system signals. Such that, increasing the adaptation gain can dramatically enhance the performances for both transient and steady state responses. Finally, the validity and the effectiveness of the controller is tested using a numerical simulation.

For reduce the high inrush current caused by the low impedance of the resonant tank of LLC resonant converter during the start-up process, this paper proposes a PWM strategy based on the event triggered control (ETC) method. In order to select the trigger event, the segmented state space modeling is used to analyze the relationship between the system state variables and the driving signals. Then, it selects the current and the capacitor voltage in the resonant tank to establish the ETC function to obtain the PWM strategy for the start-up process. When the output voltage is gradually established, the amplitude of the resonant current will be less than the pre-set threshold. Then the resonant capacitor voltage can be used to trigger the event. Finally, by comparing with the experimental results using the traditional soft start-up strategy, the proposed PWM strategy can limit the current and the capacitor voltage in the resonant tank during the start-up process to below the pre-set threshold, while greatly reducing the settling time of output voltage. In addition, the ETC method can achieve smooth switching from the start-up process to the steady state.

Clean energy and reduction in carbon footprint have motivated the adoption of Fuel Cells as an alternative source of energy, merely having any detrimental byproducts. In this work, the control of the Proton-exchange membrane fuel cell (PEMFC) integrated boost converter has been carried out. State-feedback with integral-based controllers has been designed using the classical pole placement method and optimal linear quadratic regulator approach. The first method aims at achieving the desired performance. The second method also minimizes the error while optimizing the control effort. In this approach, the control energy required for attaining the time and frequency domain objective at steady state operation is also optimized. The same avoids the limitation of existing schemes by avoiding sub-optimal solutions. Both control techniques have been verified in terms of transient performance during the load disturbance using numerical simulations and experimentation. In addition, comparative state trajectories and overall efficiency analysis of the system are presented.

The cascaded H-bridge (CHB) low-capacitance stat- ic compensator (LC-StatCom) has a limited inductive region compared to a conventional StatCom, both in balanced and unbalanced conditions, due to the inherent large oscillations on the capacitor voltages. This paper presents a detailed analysis of the viable operating region in these converters that takes into account the inherent large oscillations. The analysis facilitates sizing of the dc-link capacitors to ensure that the StatCom is able to inject a given range of positive- and negative-sequence current. Though the analysis is generic and applicable to the CHB StatComs with relatively large capacitance values, it is more relevant in the LC-StatComs. In addition, the paper derives reference steady-state signals that can be used as feedforward terms in LC-StatCom control loops to enhance the control performance. The paper presents simulation and experimental results, in balanced and unbalanced conditions to corroborate the proposed analysis.

The local scour around bridge piers is one of the main causes of bridge failures. In this study, scour hole dimensions around circular bridge piers were investigated under clear water scour conditions for various steady flow rates. The experiments were performed with four different bridge pier diameters and seven different flow rates by using uniform sediment with a median diameter of 1.63 mm and geometric standard deviation of 1.3. After each experiments the bathymetry of scour hole was determined. New empirical equations to estimate scour hole length, scour hole width and scour hole volume (V) are proposed by using experimental findings and experimental data available in the literature. The experimental results were also compared with those calculated using several empirical equations given by previous studies. Since there is a lack of data about scour hole dimensions, the experimental findings presented in this study are useful for the researchers investigating the local scour process, and have contributed to the few experimental data in the literature.

Recently, an extremum-seeking control (ESC) approach has been developed for optimization of generically time-varying steady-state responses of nonlinear systems. A generic filter structure was introduced, the so-called dynamic cost function, which has been instrumental in facilitating the use of ESC in the more generic, time-varying context. However, the dynamic cost function must operate sufficiently slow compared to the time-varying nature of the system responses, thereby compromising the convergence speed of the ESC scheme. In this work, a modified ESC approach is proposed that incorporates explicit knowledge about the user-defined dynamic cost function, able to enhance the convergence speed of the ESC scheme. Moreover, we provide a stability analysis for this extended approach. The main contribution of this work is the experimental demonstration of both ESC approaches for the performance optimal tuning of a variable-gain control (VGC) strategy employed on a high-accuracy industrial motion stage setup, exhibiting generically time-varying steady-state responses. VGC is able to enhance the system performance by balancing the typical linear control tradeoff between low-frequency disturbance suppression properties and sensitivity to high-frequency disturbances in a more desirable manner. We experimentally show that, for the unknown disturbance situation at hand, the variable-gain controller can be automatically tuned using both ESC approaches to achieve the optimal system performance. In addition, enhanced convergence speed with the modified ESC approach is evidenced experimentally.

Matrix converter (MC) rotating vector (RV) has the natural advantage for common-mode voltage (CMV) minimization. However, the application of RV in direct torque control (DTC) strategy for motor drive system is limited, mainly due to the extensive torque ripple and current distortion. To improve the steady state torque and current performance of the traditional RV-based DTC, a novel RV- based DTC method is proposed in this paper. According to the analysis of the angle offset between stator flux and the candidate voltage vector, the vector plane is divided into 12 sectors, and virtual vector synthesized by two adjacent rotating vectors is employed to fill in the blank sectors. Based on this, a 12 sector- switching table combined with a novel mapping table of rotating vectors are established to fulfill the proposed RV-DTC method. Experiments are carried out to verify the proposed method. The results show that compared with the traditional RV-DTC, steady state torque and current performances are evidently improved with the proposed RV-DTC at approximate switching frequency, while zero CMV is reserved.

The application of extremum seeking control (ESC) algorithm to antilock braking systems (ABSs) is attractive for maximizing the longitudinal frictional force. Most currently reported results suffer from the drawback of steady state oscillations around the extremum or the need to have the gradient information. In this paper, a new ESC algorithm is proposed for application to ABSs to overcome these two drawbacks. The proposed algorithm is based on a novel dynamic nonlinear gradient observer (DNGO) and a longitudinal frictional force estimator. The performance and the ultimate boundedness of the proposed ESC, DNGO and the force estimator are analysed. The proposed method is validated by simulation for dry and wet road surfaces and compared with two established results. The method is further validated on an experimental setup in the laboratory for dry and oily surfaces.

A novel widely-linear quaternion multibandstructured subband adaptive filter (WL-QMSAF) algorithm is proposed for further enhancing the convergence rate of estimation error when input signals are greatly correlated in the quaternion domain. Using the derivative rule in GHR-calculus, the WLQMSAF algorithm is developed on the basis of the principle of minimum fluctuations. The proposed WL-QMSAF algorithm decomposes the input signal into multiple parallel channels to promote more effective signal processing. Since quaternion widely linear model is able to describe complete second-order statistics of input signal, the proposed algorithm can effectively process both Q-proper and Q-improper signals. In addition, the analysis of mean-square steady state for the WL-QMSAF algorithm is performed according to the principle of energy conservation. Finally, numerical simulations are conducted on circular data as well as noncircular data to support the steady-state analysis of mean-square error as well as validate the effectiveness of the proposed WL-QMSAF algorithm.

The closed-loop fluxgate current transducer (CFCT) is the only current sensor whose measurement accuracy can reach a level of the parts per million (ppm) at present. However, the false balance, which makes the CFCT unable to work, caused by an excessive offset current is the inherent flaw of the CFCT. The high di/dt (rate of current change) of the primary current is the main factor resulting in the offset current overload. Therefore, the CFCT is currently only applied for steady-state direct-current measurements. In this article, an approach is proposed to eliminate the false balance of the CFCT in the dynamic process by adding a feedforward branch, which provides a follow-up bias point for the CFCT to make the CFCT always work in a small-signal range, where a risk of magnetic saturation does not arise. The zero-flux state of the CFCT still only depends on the feedback branch, so its high measurement accuracy is maintained. The experiments prove that the CFCT can measure a flat-top pulsed current with an accuracy of the ppm level by this method.

We study the convergence properties of Social Hegselmann-Krause dynamics, a {variant} of the Hegselmann-Krause (HK) model of opinion dynamics where a physical connectivity graph that accounts for the extrinsic factors that could prevent interaction between certain pairs of agents is incorporated. As opposed to the original HK dynamics (which terminate in finite time), we show that for any underlying connected and incomplete graph, under a certain mild assumption, the expected termination time of social HK dynamics is infinity. We then investigate the rate of convergence to the steady state, and provide bounds on the maximum $\epsilon$-convergence time in terms of the properties of the physical connectivity graph. We extend this discussion and observe that for almost all $n$, there exists an $n$-vertex physical connectivity graph on which social HK dynamics may not even $\epsilon$-converge to the steady state within a bounded time frame. We then provide nearly tight necessary and sufficient conditions for arbitrarily slow merging (a phenomenon that is essential for arbitrarily slow $\epsilon$-convergence to the steady state). Using the necessary conditions, we show that complete $r$-partite graphs have bounded $\epsilon$-convergence times.

The speed regulation problem with only speed measurement is investigated in this paper for a permanent magnet direct current (DC) motor driven by a buck converter. By lumping all unknown matched/unmatched disturbances and uncertainties together, the traditional active disturbance rejection control (ADRC) approach provides an intuitive solution for the problem under consideration. However, for such a higher-order disturbed system, the increase of poles for the extended state observer (ESO) therein will lead to drastically growth of observer gains, which causes severe noise amplification. This paper aims to propose a new model-based disturbance rejection controller for the converter-driven DC motor system using output-feedback. Instead of estimating lumped disturbances directly, a new observer is constructed to estimate the desired steady state of control signal as well as errors between the real states and their desired steady-state responses. Thereafter, a controller with only speed measurement is proposed by utilizing the estimates. The performance of the proposed method is tested through experiments on dSPACE. It is further shown via numerical calculations and experimental results that the poles of the observer within the proposed control approach can be largely increased without significantly increasing magnitude of the observer gains.

Modular multilevel converters (MMCs) are vulnerable to DC short-circuit faults. Analytical estimation of the AC and DC short-circuit currents in the AC in-feed steady-state stage is essential to reveal fault mechanisms and design protections. However, the nonlinearity of the MMC has brought significant difficulties to the calculation. This paper proposes a novel analytical calculation method for the steady-state AC and DC short-circuit currents. First, various working modes of the MMC in the AC in-feed stage are specified, and the relations between the arm current and the short-circuit current in each mode are studied. Subsequently, the arm current is divided into multiple sub-intervals, and the analytical expressions of the steady-state AC and DC fault current are deduced by solving the arm current in the sub-intervals one by one. Moreover, the derived expressions are further optimized considering the resistive-inductive (R/X) characteristic of AC grids, making them applicable for various scenarios. These analytical expressions intuitively show the relations between the system parameters and the short-circuit currents, thus can guide the rating and tuning of protection devices and power equipment. Finally, the effectiveness of the derived expressions is verified, and the influences of the system parameters on the fault currents are discussed.

In this paper, a computational method for solving for the one-dimensional heat conduction temperature field is proposed based on a data-driven approach. The traditional numerical solution requires algebraic processing of the heat conduction differential equations, and necessitates the use of a complex mathematical derivation process to solve for the temperature field. In this paper, a temperature field solution model called HTM (Hidden Temperature Method) is proposed. This model uses an artificial neural network to establish the correspondence relationship of the node temperature values during the iterative process, so as to obtain the "Data to Data" solution. In this work, one example of one-dimensional steady state and three examples of one-dimensional transient state are selected, and the calculated values are compared to those obtained by traditional numerical methods. The mean-absolute error(MAE)of the steady state is only 0.2508, and among the three transient cases, the maximum mean-square error(MSE) is only 2.6875, indicating that the model is highly accurate in both steady-state and transient conditions. This shows that the HTM simulation can be applied to the solution of the heat conduction temperature field. This study provides a basis for the further optimization of the HTM algorithm.

Although there is evidence that 5-HT acts as an excitatory neuromodulator to enhance maximal force generation, it is largely unknown how 5-HT activity influences the ability to sustain a constant force during steady-state contractions. A total of 22 healthy individuals participated in the study, where elbow flexion force was assessed during brief isometric contractions at 10% maximal voluntary contraction (MVC), 60% MVC, MVC, and during a sustained MVC. The selective serotonin reuptake inhibitor, paroxetine, suppressed physiological tremor and increased force steadiness when performing the isometric contractions. In particular, a main effect of drug was detected for peak power of force within the 8-12 Hz range (p = 0.004) and the coefficient of variation (CV) of force (p < 0.001). A second experiment was performed where intermittent isometric elbow flexions (20% MVC sustained for 2 min) were repeatedly performed so that serotonergic effects on physiological tremor and force steadiness could be assessed during the development of fatigue. Main effects of drug were once again detected for peak power of force in the 8-12 Hz range (p = 0.002) and CV of force (p = 0.003), where paroxetine suppressed physiological tremor and increased force steadiness when the elbow flexors were fatigued. The findings of this study suggest that enhanced availability of 5-HT in humans has a profound influence of maintaining constant force during steady state contractions. The action of 5-HT appears to suppress fluctuations in force regardless of the fatigue state of the muscle.

Strain measurements by gauges can play an important role in analyzing the fatigue damage of the hydroelectric turbine runner. However, these measurements cannot cover every steady-state operating condition due to the experimental limitations. Thus, the aim of this research is to predict the strain signal on runner over every possible steady operating condition using available experimental measurements. The strain signal measured during steady state involves several components (such as periodicity, vortex rope component and stochastic components) which can generate difficulties during the prediction. This paper proposes a solution to predict the runner strain signals by independently interpolating each physical phenomenon over different turbine operating conditions. These components are extracted using cyclostationary decomposition operators. A case study is performed on a Francis hydroelectric turbine to verify the interpolation performance. The proposed methodology can contribute to the fatigue assessment and help to reduce the requirements of infield measurements.

In this brief, a new discrete-time implementation is proposed for the super-twisting control with a semi-implicit Euler method. In contrast to the conventional realization methods, the proposed implementation scheme exploits two signum functions in the super-twisting algorithm (STA) such that the numerical chattering is totally avoided and the control precision is enhanced in terms of smallest control errors in the steady state. It has an advantage that the control accuracy is insensitive to the gain overestimation of STA, which benefits the gain tuning of the STA in practice. These superiorities of the proposed scheme are demonstrated through simulations and comparisons with other state of the art relevant to STA realization methods.

We present a quantitative study of phase entrainment by periodic visual stimuli in a biologically inspired neural network. The objective is to understand the neuronal population dynamics that underlie phase entrainment of brain oscillations by external stimuli, which is used for therapeutic treatment in neurological disorders, for example in Parkinsonian tremor. Yet, the neuronal dynamics underpinning such entrainment is not fully understood. Rhythmic sensory stimulation is one way of studying phase synchronization in the brain. A recent experimental study has reported phase entrainment of brain oscillations during steady state visually evoked potentials (SSVEP), which are scalp electroencephalogram corresponding to periodic stimuli. We have simulated SSVEP-like signals corresponding to periodic pulse input to our in silico model. We have used phase locking values, normalised Shannon entropy and conditional probability as synchronisation indices to show phase synchrony in the neuronal populations. Our experiment demonstrates that the phase synchronisation disappears with jitter in the input inter-pulse intervals, and this would not be the case if the output signal were to be the superposition of the responses to the different input signals. Thus, the phase synchronisation implies entrainment of the network response by the periodic input. Overall, our study shows the plausibility of using biologically inspired in silico models, validated by experimental works, to understand and make testable predictions on brain entrainment as a therapeutic treatment in specific neurological disorders., Comment: 36 pages, 10 figures

The control design for juggling a devil-stick between two symmetric configurations is proposed. Impulsive forces are applied to the devil-stick at the two configurations; and impulse of the force and its point of application are modeled as the control inputs. The dynamics of the devil-stick is described by a single return Poincare map and it is shown that the control objective of juggling can be achieved by stabilizing a hybrid orbit. The impulse controlled Poincare map (ICPM) approach, recently proposed for stabilization of continuous-time orbits of underactuated systems, is extended to achieve asymptotic stabilization of the hybrid orbit. The applicability of the ICPM approach to devil-stick juggling is demonstrated through numerical simulations.

In this paper, a 13-level asymmetric configured cascaded H-bridge (CHB) inverter is used with a 54-pulse AC-DC converter to feed a medium voltage indication motor (IM). A thorough analysis is caried out to design an isolated multi-winding transformer (MWT) based 54-pulse converter. Accordingly, the main aim of this converter is to extract the power from the grid as per the power quality standard. Moreover, a higher number of voltage levels in CHB inverter is used to adhere the power quality due to asymmetric DC supplies, having 1:2:3 voltage ratio. Hence, a 13-leevl CHB-MLI is implemented with nine DC voltage sources. The converters of this drive system ensure that the quality of the grid currents and drive currents are excellent and meet the IEEE 519 power quality successfully. A nearest level control technique is implemented to generate the switching logic for a 13-level CHBCHB inverter. Simulated results demonstrate the performance of a 298.4kW induction motor drive in steady state and dynamic state. A validation study is conducted on an experimental setup with a 7.5kW IM at steady and dynamic states. Test results show a good agreement in terms of total harmonics distortions, power loss, and efficiency.

International audience; The objective of this study is to investigate the steady and dynamic rheological behavior and characteristics of fine-grained sediments. A series of laboratory tests were conducted using an Anton Paar MCR 102 rheometer to investigate the rheological properties of the fine-grained sediments at various water to solid (W/S) ratios. In the steady-state measurement condition, the results indicate that fine-grained sediments are a non-Newtonian viscous fluid, and the presence of yield stress of fine-grained sediments is evident and is influenced by the W/S ratios. For the determination of yield stress, two types of methods were used: by defining the minimum value of shear stress from flow curves experimental data in semilog scale and by modeling the flow curves following different rheological models. From the results obtained, it appears that the Casson model was the best one to characterize the rheological behavior of fine-grained sediments, because of its high coefficient of determination R-2 and the lowest mean absolute percentage error, also close to the measured yield stress value. In the dynamic state measurement condition, the loss modulus (G '') is markedly smaller than the elastic modulus (G '), indicating that fine-grained sediments are predominantly elastic (in the range of amplitude and frequencies explored). The complex viscosity (eta*) sharply decreases with the frequency increase, but the frequency dependence of the G ' and G '' is rather weak. The G ', G '', eta*, and loss factor (tan delta) significantly reduced with the increase of the W/S ratio. In the end, the dynamic rheological properties of fine-grained sediments can be expressed as appropriate functions of the W/S ratios. This study not only provided a guideline for having a better understanding of the rheology of fine-grained sediments but will also provide scientific support for understanding and solving all kinds of natural and manmade activities involving fine-grained sediments, such as dredged sediments handling and transport by pipelines, landslides caused by rainfall or earthquake; generation and movement of mudflows, laying and maintenance of submarine cables and pipelines, and deep-sea mining engineering.

Sinusoidal waveforms as explained in Chap. 3 have an amplitude r, a frequency ω, and a phase shift or phase angle ϕ and are expressed as

We study the diffusion of a true and a false message (the rumor) in a social network. Upon hearing a message, individuals may believe it, disbelieve it, or debunk it through costly verification. Whenever the truth survives in steady state, so does the rumor. Communication intensity in itself is irrelevant for relative rumor prevalence, and the effect of homophily depends on the exact verification process and equilibrium verification rates. Our model highlights that successful policies in the fight against rumors increase individuals’ incentives to verify. (JEL D83, D85, L82, Z13)

Volume of distribution at steady state (Vss) is an important pharmacokinetic endpoint. In this study we apply machine learning and conformal prediction for human Vss prediction, and make a head-to-head comparison with rat-to-man scaling, allometric scaling and the Rodgers-Lukova method on combined in silico and in vitro data, using a test set of 105 compounds with experimentally observed Vss.The mean prediction error and % with

In this article, the stabilization problem of mismatched disturbance systems with or without time delays is studied via observed-based sliding mode control (SMC). Two kinds of SMC schemes for systems with time delay and without time delay are considered, respectively. When time delay is addressed in the system, an SMC strategy is structured via disturbance observer, where the unknown external disturbances are supposed to be generated by an exogenous dynamic. When time delay is not addressed, an SMC approach is designed in which the unknown external disturbances are assumed to tend to a constant steady state in infinite time. Sufficient conditions for stability of the corresponding sliding motion are derived by using Lyapunov–Krasovskii functional and Lyapunov function approach, respectively. Our results can be applied when the bound of the disturbances are unmeasured or unknown. Two simulation examples are shown to illustrate the proposed methods.

This article proposes a controller for dc–dc converters to achieve fast load-transient responses. The controller is developed for both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) of operation. The main idea is developed for buck converters, but it is shown that the proposed controller can be applied to other topologies, such as the noninverting buck–boost converter. The controller derivation, analysis, and experimental verifications are provided in both CCM and DCM, and its performance is compared with other methods. The main advantage of the proposed controller is that it minimizes the recovery times associated with load-transient responses in dc–dc converters while maintaining component sizes and other system parameters within the acceptable range. The proposed controller can be used to minimize load transients in electronic portable devices and electric vehicle charging.