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Remaining useful life (RUL) prediction has been increasingly considered in many industrial fields for the reliability and safety of their systems. As a data analysis tool of deep learning, deep convolutional neural network (CNN) shows great potential for RUL prediction. This paper proposes an intelligent RUL prediction method based on a double-CNN model architecture. Given the powerful feature extraction capability of CNN, the proposed method is fed with original vibration signals with no need to resort to any feature extractor, which can also retain the useful information in maximum. The prediction includes two stages: first, incipient fault point is identified by the first CNN model and a proposed “3/5” principle; then, the second CNN model is constructed for RUL prediction. In practice, RULs of identical components are different from each other, which poses a major challenge in RUL prediction. To overcome this problem, an intermediate reliability variable is first calculated in this paper, instead of directly predicting the RUL value. Then, a mapping algorithm is proposed to map reliability to RUL. To demonstrate the effectiveness of the proposed method, data of four tests of bearing degradation are utilized for RUL prediction. Compared with state-of-the-art methods, the proposed method shows higher prediction accuracy and robustness. The prediction results and evaluation indexes demonstrated the effectiveness and superiority of the proposed method. [ABSTRACT FROM AUTHOR]

Thanks to the advantages of high power density and the capacity of bidirectional power transfer, the CLLC resonant converter is widely used in the hybrid ac–dc microgrid as a dc transformer to interlink the ac and dc bus. Since the voltages of ac and dc bus are controlled by the energy management system, the CLLC resonant converter operates under open-loop condition, which means the switching frequency and duty cycle are fixed. As a result, in the hybrid ac–dc microgrid applications, for the CLLC converter, the main concern is not the voltage regulation but the conversion efficiency. This paper focuses on the total power loss optimization and the magnetic design of the CLLC resonant converter based on artificial intelligence (AI) algorithm. In order to optimize the total power loss, an AI algorithm-based two-stage optimal design method is proposed. In the first stage, the total power loss, including the driving loss, turn-off loss, conduction loss of the switches, the power loss of the resonant capacitances, and copper and core loss of the transformer are optimized by the proposed AI algorithm, GA+PSO, and the optimal parameters, including the leakage inductances (Lr1 and Lr2), magnetizing inductance (Lm), and resonant capacitances (Cr1 and Cr2) are derived. In the second stage, the optimal leakage inductances and magnetizing inductance are realized by setting proper distance between the primary winding and the secondary winding (dw), and the thickness of the air gap (da). As for the magnetic design, in this paper, the leakage inductances of a planar transformer are used as the resonant inductances. The equations of dw and da to achieve the optimal leakage inductances and magnetizing inductance are derived. Both the proposed optimal design method and the equations of dw and da are validated by simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper is mainly focusing on the problem of high-accuracy tracking control design for a class of nonlinear systems subject to mismatched uncertainties. A novel asymptotic control framework is presented. This is achieved by developing an estimator-based controller with an observer-based estimator, which is applied to precisely estimate all the system uncertainties. It is proved that the overall tracking system can be asymptotically stabilized. The estimation error of the system uncertainties is also ensured to be asymptotically stable. The main contribution of this paper is that the proposed solution can control a more representative class of nonlinear systems. Another key feature of this control framework is that the incorporated observer-based estimator can eliminate the assumption that system uncertainties should vary slowly or even have no variation in the existing estimators for uncertainties. This superior tracking control property of the scheme is validated by a robotic manipulator example. [ABSTRACT FROM AUTHOR]

From the practical perspective, with large-scale cargoes or nonnegligible hook masses, the centers of gravity of cargoes and hooks do not coincide with each other, and shipboard cranes usually exhibit complex double-pendulum effects during ship-to-ship or ship-to-harbor transportation, which dramatically increase the complexity of dynamic characteristics and make the control issue very challenging. At present, there is no reported work on control of double-pendulum shipboard cranes yet. To tackle such problems, this paper obtains the dynamic model of double-pendulum shipboard cranes and then provides an effective nonlinear antiswing feedback controller to achieve stable cargo transportation. Specifically, new state variable signals are generated by combining the original state variables with the ship motion (induced by sea wave perturbations). Based on this, by adding some elaborately designed nonlinear terms, an antiswing feedback controller is proposed, which can achieve stable transportation with suppressed swing, and the closed-loop asymptotic stability is proven without any linearizations or approximations to the original complex nonlinear dynamics, with rigorous theoretical analysis. As far as we know, the paper provides the first solution for both controller design and stability analysis of double-pendulum shipboard cranes. Also, several groups of hardware experiments are implemented on a self-built hardware experiment platform, which verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Linear induction motors (LIMs) have been extensively adopted in urban railway transportation given their nonadhesion thrust and simple stator structure. However, these LIMs undergo unfavorable power factor and efficiency considering their copper and eddy losses. Recently, linear flux-switching permanent-magnet motors (LFSPMs) have attracted the attention of researchers due to their high power density, simple structure, easy heat dissipation, high efficiency, and high power factor. However, so far, no quantitative comparison exists between LFSPMs and LIMs of the size 1:1 to prove the feasibility of LFSPMs to be used in railway transit systems. Therefore, a comparative analysis between the two motors is conducted in this paper. First, this paper investigates the LIMs for railway transit using the finite element method (FEM). Second, the LFSPMs for railway transit is designed and optimized. Third, the electromagnetic performance of the two motors is compared and analyzed through the FEM. Finally, a small-sized prototype of the LFSPMs is constructed to validate the FEM results. It is concluded that LFSPMs offer a favorable thrust force, have high efficiency, and high power factor but have large normal force and force ripple. Therefore, applying LFSPM requires a reliable supporting device and a shock absorber. [ABSTRACT FROM AUTHOR]

Turbomolecular pumps with ultrahigh vacuum performances are a desired technology among modern vacuum systems, which requires the pump to synchronously possess the wide pumping speed and high vacuum. This paper describes a systematic design methodology for a magnetically levitated turbomolecular pump with consideration of multiphysics constraints, such as the mechanical strength, rotor dynamics, electromagnetic losses, and thermal characteristic. These variables will directly decide the acquisition of high vacuum performances. The design process for such high-performance pumps requires multidisciplinary and highly iterative due to the complex interaction of the many design variables involved. The structure of the bladed rotor is determined in terms of the material selection and mechanical verification. In this paper, an effective modeling method is presented to achieve accurate bending modes of the bladed rotor. An assessment on the loss level and the thermal limit is performed to ensure the temperature rise of the pump within the acceptable range. The measured results show that the pump can achieve the high vacuum performance with the pumping speed of 4370 l/s and the lowest working pressure of 10–8 magnitude. The proposed design process described in this paper provides the general guidelines for the multidisciplinary design of high-performance turbomolecular pumps. [ABSTRACT FROM AUTHOR]

This paper presents a six-step mode-combined field-weakening control scheme to improve the maximum output torque of induction motor (IM) in the voltage-extension region. Compared with the conventional inscribed circle and hexagon methods, the proposed six-step mode method can increase the utilization of dc-link voltage, leading to extended maximum output torque capability. However, the six-step mode operation will inevitably result in torque ripple and current harmonic. To figure out the quantitative relation between the torque extension and ripple, an “equivalent-circuit”-based method is proposed for theoretical torque analysis in six-step mode. To cut off the main current harmonic (sixth harmonic), a second-order generalized integrator based band-stop filter is designed for the feedback current in the current loop. The designed filter can achieve IM stable operation in a six-step mode without affecting the bandwidth of the current loop. The experimental results from a 3.7-kW IM setup verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In recent years, many deep-network-based super-resolution techniques have been proposed and have achieved impressive results for 2 ${\times }$ and higher magnification factors. However, lower magnification factors encountered in some industrial applications have not received special attention, such as 720P-to-1080P (1.5 ${\times }$ magnification). Compared to traditional 2 ${\times }$ or higher magnification factors, these lower magnifications are much simpler, but reconstructions of high-definition images are time-consuming and computationally complex. Hence, in this paper, a fast image upsampling method is designed specifically for industrial applications at low magnification. In the proposed method, edge and nonedge areas are first distinguished and then reconstructed via different fast approaches. For the edge area, a local edge pattern encoding-based method is presented to recover sharp edges. For the nonedge area, a global iterative reconstruction with texture constraint is utilized. Moreover, some acceleration strategies are also presented to further reduce the complexity. The experimental results demonstrate that the proposed method can obtain performance comparable to that of some state-of-the-art methods for 720P-to-1080P magnification, but the computational cost is much lower. [ABSTRACT FROM AUTHOR]

A space vector modulation (SVM) technique of a dual-inverter system for an open-end winding motor drive is described in this paper, where one inverter has a battery power source and the other has an only capacitor across the dc bus. The SVM must be achieved to operate the motor with field-oriented control and simultaneously to control the capacitor voltage at a constant value by using redundant switching states of the dual-inverter system. The control of the capacitor voltage is carried out by selecting a charging or a discharging mode in each redundant switching state, taking the instantaneous motor power factor into account. In addition, it is also required to reduce the error voltage pulses, which are generated in output multilevel voltage waveforms during the dead time. The compensation method of the existing dead-time scheme and the improved SVM sequence to reduce the error voltage vectors are proposed in this paper. The proposed methods are examined through several experimental tests and are confirmed to generate superior output voltage waveforms from the viewpoint of the measured total harmonic distortion and dv/dt. [ABSTRACT FROM AUTHOR]

Manual assembly is still an essential part in modern manufacturing. Understanding the actual state of the assembly process can not only improve quality control of products, but also collect comprehensive data for production planning and proficiency assessments. Addressing the rising complexity led by the uncertainty in manual assembly, this paper presents an efficient approach to automatically capture and analyze hand operations in the assembly process. In this paper, a detection-based tracking method is introduced to capture trajectories of hand movement from the camera installed in each workstation. Then, the actions in hand trajectories are identified with a novel temporal action localization model. The experimental results have proved that our method reached the application level with high accuracy and a low computational cost. The proposed system is lightweight enough to be quickly set up on an embedded computing device for real-time online inference and on a cloud server for offline analysis as well. [ABSTRACT FROM AUTHOR]

This paper is concerned with parameter learning of chips with small outline transistor (SOT) package, which is one of the most widely used package in surface mount technology (SMT) and has various subcategories. Previously learned parameter is crucial to most SOT-related industrial applications, such as location and defect inspection. However, parameter learning is a challenging work because of package diversity and image-quality deterioration in practical industrial applications. The conventional methods, checking data sheet or manual measuring, cannot meet the accuracy requirement of SMT. This paper proposes a hierarchical-backtracking-based parameter learner for SOT chips. The Gaussian mixture model based clustering algorithm and random walker algorithm are firstly applied to extracting lead regions of SOT chip; Then, chip models are inferred by grouping these lead regions with a hierarchical backtracking algorithm. Finally, redundant models are eliminated with root set pyramids and the valid chip model is obtained. The experimental results show that the proposed parameter learner performs well on SOT chips and is robust to noisy sets. [ABSTRACT FROM AUTHOR]

Solid state transformer (SST) integrated hybrid dc–ac microgrid (HMG) has wide operating capabilities in presence of dc–ac loads, renewable energy resources, and energy storage. This paper proposes control strategies for localized control of zonal hybrid microgrid, enabled by the SST and centralized energy storage devices (ESD) integrated using dual active bridge (DAB) converter. The control of DAB dc–dc converter is modified for zero circulating power flow (ZCPF) operation in both SST and ESD. Power management and coordination control used in this paper ensures the power supply reliability of the zonal HMG integrated through the SST. Microgrid system, along with its proposed controllers, provides a stabilized low-voltage dc and ac network ports, in both grid feeding and forming modes. The performance of the configured HMG system is evaluated under various power management scenarios using the MATLAB software platform. Further, the SST architecture, with its proposed controller, is tested on FPGA-based hardware platform. [ABSTRACT FROM AUTHOR]

This paper presents an ultra-high-frequency (UHF) passive sense tag for electrical grid and substation thermal monitoring, with emphasis on the tag system optimization and the design of a low power embedded temperature sensor. The designed tag achieves a sensitivity of $-$ 12.3 dBm under active temperature monitoring operation, which is the state of the art among existing UHF passive temperature sense tag products. The sensing inaccuracy of the tag is $\pm$ 2.5 $^{\circ }$ C (3 $\sigma$) from $-$ 25 to 120 $^{\circ }$ C after a low-cost wireless single-point trim. An antimetal ceramic-packaged tag was tested by attaching to a ring main unit in the substation and complete tag system demonstrated robust wireless operation with a sensing distance of 3.5 m. The combination of batteryless and wireless operation, high sensitivity, wide sensing range, and small incident-power-dependent error ($\pm$ 0.2 $^{\circ }$ C) makes this tag suitable for the target applications. [ABSTRACT FROM AUTHOR]

Induction motor fault identification is essential to improve efficiency in industrial processes improving costs, production line, and maintenance time. This paper presents a novel motor fault detection methodology based on quaternion signal analysis. The proposed method establishes the quaternion coefficients as the value of motor current measurement, and the variables x, y, and z are the measurements from a triaxial accelerometer mounted on the induction motor chassis. The method obtains the rotation of quaternions and applies quaternion rotation statistics such as mean, cluster shades, and cluster prominence in order to get their features, and these are used to classify the motor state using the proposed tree classification algorithm. This methodology is validated experimentally and compared to other methods to determine the efficiency of this method for feature detection and motor fault identification and classification. [ABSTRACT FROM AUTHOR]

This paper proposes an improved coordinated control of standalone brushless doubly fed induction generator (BDFIG) supplying nonlinear loads. Due to the existence of nonlinear loads, the voltage at the point of common coupling becomes distorted with a large number of low-order harmonics, which severely degrades the performance of power generation systems. In order to eliminate the included low-order harmonics, a coordinated control method of harmonic mitigation has been presented in this paper for the control of both machine side and load side converters. Then, a weight factor is introduced to the proposed control method for distributing the contribution of harmonic mitigation between the two converters. Comprehensive experimental results on a 30 kVA BDFIG are presented to verify the proposed control method. [ABSTRACT FROM AUTHOR]

This paper presents a new design of round-shaped transformers applied in diode and controllable rectifiers. Despite conventional three-phase transformers, in round-shaped transformers, voltage is induced on the secondary winding by rotating magnetic field. As a result, in the secondary of this transformer, there can be more than three phases with desired shifts. On the other hand, some rectifier systems may use more bridges supplying from the secondary to improve output dc voltage. However, the rectifier systems produce undesirable current harmonics, especially in controllable systems. This paper discusses how the new design of round-shaped transformers can significantly reduce the harmonic contents of the input current by sinusoidal skewing of the secondary core. The new design is investigated in this paper and its analysis confirms that the harmonics of the input currents can be effectively reduced. Experimental results are also provided to validate the analysis carried out in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a novel integrated-stage light-emitting diode (LED) driver based on Flyback and resonant converters. The Flyback converter realizes power factor correction in the discontinuous conduction mode. The resonant converter is operated as a dc–dc converter to support the LED loads. Moreover, the resonant converter can clearly decrease the drain–source voltage of the active switch and exhibits zero-voltage-switch characteristics. Therefore, a cost-effective MOSFET can be chosen as the main control component that can decrease the cost of the whole system. Compared to a single-active-switch converter (such as Class-E converter), the number of passive components in the resonant converter can be limited to four. Therefore, the power density of the system can be improved drastically. In this paper, a 100-W prototype is presented under the experimental condition to validate the proposed integrated-stage LED driver. [ABSTRACT FROM AUTHOR]

This paper aims at the fault-tolerant adaptive control for the nonlinearly parameterized systems with mismatched disturbances. A novel adaptive control scheme is developed in this paper by adding a power integrator technique. The mismatched disturbances are estimated by a designed disturbance observer. A new fault-tolerant control method is proposed to deal with the uncertain actuator faults including actuator stuck. The proposed adaptive controller ensures that the closed-loop system is input-to-state stable. Simulation results for a robotic arm system are given to present the effectiveness of the developed control technique. [ABSTRACT FROM AUTHOR]

In this paper, a new family of impedance source inverters is presented. It employs high-frequency electrical isolation between the inverter bridge switches and the load along with voltage clamping across the dc-link voltage. Conventional Z-source inverters (ZSIs) employs an impedance network that consists of inductors and capacitors. It has unique features that realize both step-up/step-down functions and eliminates the need of dead/overlap times. This paper extends this novel concept by using electrical isolation in impedance source inverters. High-frequency isolation has many advantages in terms of immunity and reliability; when applied with impedance source inverters this makes ZSIs a preferable choice for industrial applications. In photo-voltaic systems, the addition of the high-frequency transformer provides safety by avoiding the injection of dc circulating current into the grid, without the need of an external bulky line frequency transformer. The gain of the proposed inverter design can be accurately selected by choosing the turns ratio of the high frequency transformer (HFT) or by adjusting the shoot-through duty cycle (STDC) to the inverter. This allows for greater freedom especially when utilizing a higher modulation index, with the STDC allowing dynamic gain adjusts to be done speedily during operation of the inverter. Additionally, a dc-rail voltage clamping technique for the proposed class of isolated ZSIs is also discussed. This technique provides benefits not only in improving the output voltage quality, but also in reducing voltage stress of the active and passive components by minimizing the voltage spikes across the switching devices. In this paper, several high-frequency isolated ZSIs are presented, and an example isolated improved ΓZSI design is shown and discussed in detail. Simulations are provided for the proposed class of isolated inverters to verify their working. Further experimental investigation has been done for which results for the isolated improved ΓZSI are reported. These empirical results have largely confirmed the expected benefits that were determined through simulation and accurate model-based testing. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases are the primary cause of deaths in the world. Atrial fibrillation (AF) is the most common type of cardiac arrhythmia. Due to its high prevalence and associated risks, early detection of AF is an important objective for healthcare systems worldwide. The growing demand for medical assistance implies increased expenses, which could be limited by implementing ambulatory monitoring techniques based on wearable devices, thus, reducing the number of people requiring observation in hospitals. One of the main challenges in this context is related to the large amount of data from patients to be analyzed, which points to the suitability of using computational intelligence techniques for it. The selection of the features to be extracted from data plays a key role in order for any classifier of heart rhythm to provide good results in this regard. This paper demonstrates that it is possible to achieve an accurate detection of AF using a very low number of relatively simple features extracted from photoplethysmographic signals, enabling the use of affordable wearable devices (with scarce processing and data storage resources) with this purpose over long periods of time. This fact has been validated in experiments using data from real patients under medical supervision. [ABSTRACT FROM AUTHOR]

This paper presents a Tornambe controller (TC) for a two-degree-of-freedom (DOF) parallel mechanism of pneumatic muscle actuators (PMAs) based on tracking differentiators (TDs). A dynamic nonlinear system is established for the 2-DOF parallel mechanism of PMAs. TC is designed for improving control performance of the dynamic nonlinear system. The TDs are utilized to obtain high order derivatives of tracking errors, which are required by TC. Moreover, stability analysis of the dynamic nonlinear system is shown by a Lyapunov approach. Finally, experimental results are shown to verify the effectiveness of the proposed control method in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for detection and isolation of wastegate (WG) faults in a turbocharged (TC) gasoline engine. This paper starts with a fault effect analysis on the WG faults, including WG stuck open and stuck closed, which is an early step in a detection strategy design. Then, a second-order sliding-mode observer (SOSMO) is proposed to capture the exhaust manifold dynamics. The observer uses experimentally validated engine models to estimate the WG position and a virtual force. The virtual force represents the external disturbances that disrupt the WG operation and enables the proposed SOSMO to estimate the WG position robust to the faults. Using this force, a detection and isolation algorithm is presented and experimentally verified on a modern TC gasoline engine. Test bench results show that the proposed strategy can successfully detect and isolate the two different WG faults. [ABSTRACT FROM PUBLISHER]

Vehicular ad hoc networks (VANETs) help improve traffic safety and lessen traffic congestion. Roadside units (RSUs) play a key role in serving as the event and data broker in the form of vehicle-to-infrastructure communication to supply wireless and mobile vehicle-to-vehicle communication. Recently, hybrid VANET-sensor networks have attracted much attention as events are detected by sensor nodes and are spread to a wider area via VANETs, in which the number of RSUs is restricted due to high cost. This paper investigates the problem of minimizing the total cost of deploying RSUs and sensor nodes along the two sides and the median island of a two-lane road to cover the whole road, represented as a grid, and to form a connected VANET-sensor network. This problem is NP-complete by reduction to the NP-complete placement problem for a single-lane road. Therefore, this paper formulates the problem as an integer linear program and then proposes a center particle swarm optimization approach, in which a center particle is adopted for increasing the convergence speed. Additionally, a theoretical analysis for the approach is provided. Experimental results show that the approach can perform well for moderate-sized problems. [ABSTRACT FROM PUBLISHER]

This paper proposes the design process of a 2.62-kW 150-krpm high-speed surface-mounted permanent-magnet synchronous motor. To meet the required specifications, the numbers of poles and slots were determined by considering the maximum speed and the rotary stability affected by the vibration of the rotor. In addition, this paper describes not only the appropriate material selection method but also the appropriate geometry design method based on analytic approaches. Furthermore, to precisely evaluate the bearing and windage losses at a high speed, a method that combines the finite-element method and the experiment results of the prototype was used. As a result, an improved motor was designed, which had higher maximum power and speed than the prototype and a lower mass moment of inertia. Finally, tests were conducted to verify the validity of the proposed design process and the effectiveness of the motor. [ABSTRACT FROM PUBLISHER]

In this paper, the use of the Dual Kalman Filter for the identification of photovoltaic system parameters is presented. The system includes the photovoltaic source, the dc/dc converter and the battery/dc bus and both its states and parameters in the actual operating conditions are identified. In particular, the proposed approach gives the confidence interval for the system settling time, which is used for the real-time optimization of the perturbative maximum power point tracking algorithm. The proposed technique is implemented by using a Field-Programmable Gate Array and it is validated by means of both simulation and experimental results. [ABSTRACT FROM PUBLISHER]

In recent years, design and tuning of fractional-order controllers for use in motion control have attracted much attention. This paper deals with one of the interesting methods that have been recently proposed for tuning fractional-order proportional and derivative (FOPD) motion controllers. The FOPD controller tuned based on the considered method results in simultaneously meeting the desired phase margin, the desired gain crossover frequency, and the flatness of the phase Bode plot at such a frequency. Since, in this tuning method, the derivative parameter and order are determined in a graphical way, in the first view, it is not clear for which pairs of phase margin and gain crossover frequency an FOPD controller can be found to satisfy the mentioned specifications. In this paper, necessary and sufficient conditions are presented via an analytical approach to check the solution existence of the considered tuning method in both cases of absence and presence of time delay in feedback loop. Furthermore, the uniqueness of the controller parameters obtained from the method is investigated. Moreover, some numerical and experimental examples are presented to confirm the analytical results of this paper. [ABSTRACT FROM PUBLISHER]

This paper investigates the problem of H\infty filtering for polynomial-fuzzy-model-based discrete-time networked systems under an event-triggered scheme. A polynomial fuzzy filter is designed to estimate the control output. In order to reduce the data size transmitted in a network, signal quantization is managed via a logarithmic quantizer. A novel method is designed to guarantee a filtering error system to be asymptotically stable and to satisfy the desired performance. Furthermore, sufficient conditions developed via the method are represented as a sum of squares, which can be solved by SOSTOOLS. A simulation example is provided to demonstrate the effectiveness of the proposed results. [ABSTRACT FROM PUBLISHER]

High penetration of wind energy requires fast-acting dispatchable resources to manage energy imbalance in the power grid. Battery energy storage systems (BESS) are considered as an essential tool to decrease the power and energy imbalance between the scheduled generation (day ahead forecast) and the actual wind farm output. Control methodology or battery management greatly impacts performance of the ESS. Better performance of BESS reduces the minimum required size of batteries for wind variability mitigation. This paper proposes a novel control method for BESS to fulfill a production commitment. This method, called “predictive controller,” is based on updated forecast data to improve the performance of the energy storage and consequently reduce the required size of energy storage. The Sodium–Sulfur (NaS) type battery is selected for the simulation purposes. Results show that the predictive controller reduces the error (between scheduled generation and actual wind farm output) more than the simple method (also known as minute-by-minute method) and other proposed methods in the literature. Also, a new formulation for the battery lifetime estimation is introduced, and it is used to analyze the impact of the proposed method on the battery lifetime depreciation. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to study the dynamics of a permanent magnet direct current (PMDC) brushed motor while two crucial space-domain effects, namely, slotting effect and commutation phenomenon are taken into account. Semi-analytical dynamic time-domain PMDC brushed motor model inclusive of these space-domain effects is used to analyze and investigate the dynamics. Pulse width modulation operated discontinuous current PMDC brushed motor drive with steady duty cycle is employed to acquire the bifurcation patterns. The chaotic nature due to slotting effect and commutation is identified from the bifurcation patterns and reported. It also has to be admired that such nonlinear dynamical behavior with the same set of parameters at similar operating condition has not been observed when a conventional PMDC brushed motor dynamic model is considered. These space-domain effects, namely, slotting effect and commutation also have a prominent impact to make some time-domain states of a PMDC brushed motor drive chaotic. The role of slotting effect and commutation phenomenon to analyze the chaos over time-domain state variables of the PMDC brushed motor drive is investigated and validated experimentally in this paper. [ABSTRACT FROM PUBLISHER]

The traditional evaluation method of vehicle noise can no longer meet the requirements of electric vehicle as the sound character of electric powertrain (E-PT) is totally different from that of internal combustion engine vehicles. This paper presents a complete investigation of the sound quality of an E-PT. An acoustic test is conducted to analyze the sound character of E-PT, based on which the acoustic origins of E-PT including electromagnetic noise, gear whine, and inverter switching noise are studied. After that the sound quality of E-PT is investigated by objective and subjective evaluations. Subsequently, a sound quality model of E-PT based on support vector machine is established. The relative error testifies the effectiveness of the prediction model. The influence of the main noise origins on the sound quality of E-PT is determined. Finally, the structure of gearbox housing is redesigned based on topology optimization to improve the sound quality. The main original contributions of this paper are not only the sound quality method developed for E-PT but also improvement feasibility of sound quality. [ABSTRACT FROM PUBLISHER]

A phase-locked loop (PLL) is commonly used in grid-connected power converter for synchronization. A single input single output (SISO) linear model of PLL with the phase angle of the point of common coupling (PCC) voltage as input and the estimated phase angle as the output is generally used in the PLL analysis and design. However, an undesirable coupling between the magnitude and phase of the input voltage is present when a filtering stage is incorporated before the control loop, which a SISO model cannot capture, and could result in a significant disturbance in the PLL estimated phase during grid faults. This paper proposes a generalized multi-input multi-output (MIMO) linear model that captures the complete PLL dynamics during symmetrical faults for a PLL equipped with any prefilter. Furthermore, a compensation method that decouples the magnitude dynamics of the input voltage from the phase dynamics is proposed in this paper. The proposed compensation improves the PLL's phase tracking performance by ensuring that the prefiltered PLL acts only on the PCC voltage phase changes. A vital application of the proposed compensation method for PLL is during a grid fault case, wherein the converters are expected to contribute to the fault current, which requires an accurate measurement of the PCC voltage phase. The compensation method's effectiveness is demonstrated using power hardware in the loop simulation of a hardware voltage source converter interfaced to a distribution system simulated in real-time. [ABSTRACT FROM AUTHOR]

Conventional ultrasound probes have inherent limitations in some application scenarios. Because of their fixed shapes and sizes, they can hardly pass through small orifices to examine the target closely. With the recent development of microelectromechanical systems and flexible electronic technologies, collapsible and self-assembling devices are being considered as a potential approach to address this problem. This article presents an innovative transformable ultrasonic transducer (TUT), which can transform between a one-dimensional (1-D) linear array and a 2-D planar array with the ability of switching between different functions including 2-D/3-D imaging and high-intensity focused ultrasound beamforming. The transforming process is accomplished with a specially designed flexible printed circuit board inspired by a paper-folding mechanism. The electrical and acoustic properties of the developed transducer along with the acoustic field distribution in its different forms have been characterized. The 2-D/3-D imaging performances of the TUT have been also evaluated under 1-D and 2-D configurations, respectively. In addition, the performance of a focused concave transforming mode has been also discussed. The evaluation results suggest that TUT can maintain its performance under different structures with precise transforming control. The TUT device has the potential to considerably expand the applications of industrial and clinical ultrasound. [ABSTRACT FROM AUTHOR]

The twenty-one papers in this special section focus on bringing the ideas of the worldwide research community working on various disturbance/uncertainty estimation and rejection methods in different engineering sectors into common platform and to present the latest advances and developments in design methods for disturbance/uncertainty estimation, design methods for disturbance/uncertainty attenuation, stability and performance analysis, practical implementation, and various case studies of the applications of these techniques. [ABSTRACT FROM PUBLISHER]

Energy efficiency of locomotion is a significant issue for autonomous mobile robots. This paper focuses on the pace gait ladder descent motion that has a closed kinematic chain formed by the robot links and the environment. To reduce the energy cost in the closed kinematic chain, we propose an optimal control strategy by optimizing the internal stress and motion trajectories in parametric form. As the main contributions of this paper, three types of energetically efficient ladder descent motions are generated with different motion-mode assumptions. Critical factors, including cycle time, horizontal distance between the robot and the vertical ladder, and value of internal stress, are analyzed theoretically. Simulation and experimental results indicate that the proposed control strategy is effective for planning an energetically efficient ladder descent motion. [ABSTRACT FROM PUBLISHER]

This paper deals with the control of a hybrid source combining a proton exchange membrane fuel cell and supercapacitors. To achieve this objective, an interconnection and damping assignment passivity-based control in a sampled-data context is implemented. This paper first details with this new controller and shows that it ensures the stabilization of the hybrid system at its desired equilibrium point under large range of sampling periods. These considerations are followed by a detailed discussion on experimental results achieved on a 1.2-kW test bench. [ABSTRACT FROM PUBLISHER]

This paper gives an overview of the topological variations of multi-winding induction machines (IMs) and drives. The study is restricted to IMs having two distributed windings on the stator and a brushless rotor. The mathematical modeling techniques and control algorithms available in the literature are highlighted. Being magnetless and brushless, a Dual Stator Winding IM is highly reliable, maintenance free, and economic. Thus, it possesses the necessary potential to become a part of ac and dc microgrids. Recent research trend shows growth in the application of such generators for off-grid and grid-connected systems. [ABSTRACT FROM PUBLISHER]

The acquisition of information on heat inflow is essential to the control of thermal displays and the rendering of thermal sensations. This paper addresses a method of estimating the amount of heat inflow without using a heat flow sensor and demonstrates sensorless heat inflow control using a Peltier device, which is often employed as a thermal device in thermal displays. Moreover, this paper introduces a method of identifying the thermal contact resistance of the device needed for the proposed observer. The observer estimates heat inflow by using information on electrical currents and temperatures. By using the observer instead of a heat flow sensor, which generally has a larger thermal capacity than a temperature sensor, an improvement in the response of a thermal device is expected. The applicability of the proposal is tested by experiments. [ABSTRACT FROM PUBLISHER]

A hybrid switched-capacitor/interleaved boost converter able to provide a high voltage gain and to cancel the input current ripple at a preselected duty cycle was recently presented in the literature. This paper extends that work by proposing an optimized switching strategy for operating conditions at other values of duty cycle. The switching strategy effect on the converter's voltage gain and input current ripple is quantified and compared against the performance under the conventional switching strategy. The approach is validated in the laboratory through hardware prototyping. [ABSTRACT FROM PUBLISHER]

This paper presents a topology for micropower piezoelectric wind energy harvesting useful for developing self-powered wireless sensor nodes. The features of the proposed topology, as compared with the existing piezoelectric/electromagnetic topologies, are as follows: 1) delivering power at high voltage levels, particularly at low-speed air flows; 2) starting operation at low cut-in speeds (about 1 m/s); and 3) robust structure for operating at high-speed wind flows practically tested up to 20 m/s. The proposed topology consists of a small fan with embedded permanent magnets (PMs) and a piezoelectric beam with a PM proof mass, which interacts with the PMs in the fan to harvest wind power. This paper also presents an analytical model and a design procedure to determine the number of PMs in the fan and their arrangements to maximize the captured power and minimize the cut-in speed. Using a prototype of the proposed topology, it is shown that the device starts capturing wind power at the wind speeds above 0.9 m/s. It is also shown that the suggested topology is at least 10% more efficient than the existing topologies in using piezoelectric materials and that its total volume power density is higher than those of the other topologies. [ABSTRACT FROM PUBLISHER]

In order to improve the availability of wind turbines and to avoid catastrophic consequences, the detection of faults in their earlier occurrence is fundamental. This paper proposes the development of a fault diagnosis scheme relying on identified fuzzy models. The fuzzy theory is exploited since it allows approximating uncertain models and managing noisy data. These fuzzy models, in the form of Takagi–Sugeno prototypes, represent the residual generators used for fault detection and isolation (FDI). A wind turbine benchmark is used to validate the achieved performances of the designed FDI scheme. Finally, extensive comparisons with different fault diagnosis methods highlight the features of the suggested solution. [ABSTRACT FROM PUBLISHER]

This paper presents the current research trends and future issues for industrial electronics related to transportation electrification. Specific emphasis is placed on electric and plug-in hybrid electric vehicles (EVs/PHEVs) and their critical drivetrain components. The paper deals with industry related EV energy storage system issues, EV charging issues, as well as power electronics and traction motor drives issues. The importance of battery cell voltage equalization for series-connected lithium-ion (Li-ion) batteries for extended life time is presented. Furthermore, a comprehensive overview of EV/PHEV battery charger classification, standards, and requirements is presented. Several conventional EV/PHEV front-end ac/dc charger converter topologies as well as isolated DC/DC topologies are reviewed. Finally, this paper reviews various EV propulsion system architectures and efficient bidirectional DC/DC converter topologies. Novel DC/AC inverter modulation techniques for EVs are also presented. The architectures are based on the battery voltage, capacity, and driving range. [ABSTRACT FROM PUBLISHER]

Modern electric-powered vehicles include several sources and loads. This paper extends the idea of introducing multiple sources and loads into an onboard vehicular integrated power system. The proposed power conditioning system is formed around a multiwinding integrated transformer. Both inductive and capacitive elements of this magnetic component affect the power conditioning stages of the system. This paper proposes an experimental transformer modeling procedure that includes the inductive and capacitive parameters. A mathematical procedure is developed, simplifying this more detailed experimental model of the multiwinding transformer into a $\Pi\ RLC$ circuit that can be utilized in the system transient analysis. The modeling method is applied to a three-winding transformer and is verified through simulations and experiments. [ABSTRACT FROM PUBLISHER]

The phasor-PWM-based current source inverter (CSI) is a boost inverter. The difference between conventional CSIs and the boost inverter is that the boost ratio (VLLrms/Vdc ) in the boost inverter can easily be above 3.0, whereas this ratio is around 1 in conventional CSIs. In order to realize the potential capabilities of the boost inverter and to assist its penetration into renewable energy systems, the boost inverter dynamic behaviors are studied in this paper. First, the large- and small-signal models as well as the dq-equivalent circuits of the boost inverter are presented. Then, the developed models are verified using circuit simulations and experiments on a laboratory-scale 2-kW 208/240- V_{\rm LLrms} V_{\rm dc}=65\ \hbox{V} $ boost inverter made of reverse-blocking IGBTs. Finally, the developed small-signal model is used to study the stability of the boost inverter through root locus of small signal poles (eigenvalues) as control inputs, and load parameters vary within the boost inverter's operating limits. [ABSTRACT FROM PUBLISHER]

In recent years, renewable energy has developed to address energy security and climate change drivers. However, as energy resources, they possess a variable and uncertain nature that significantly complicates grid balancing operations. As a result, an extensive academic and industrial literature has developed to determine how much such variable energy resources (VERs) may be integrated and how to best mitigate their impacts. While certainly insightful with the context of their application, many integration studies have methodological limitations because they are case specific, address a single control function of the power grid balancing operations, and are often not validated by simulation. The prequel to this paper presented a holistic method for the assessment of power grid imbalances induced by VERs based upon the concept of enterprise control. This paper now systematically studies these power grid imbalances in terms of five independent variables: 1) day-ahead market time step; 2) real-time market time step; 3) VER normalized variability; 4) normalized day-ahead VER forecast error; and 5) normalized short-term VER forecast error. The systematic study elucidates the impacts of these variables and provides significant insights as to how planners should address these independent variables in the future. [ABSTRACT FROM PUBLISHER]

This paper addresses the problem of thermal energy control in shopping centers through the application of model predictive control (MPC) strategies. In particular, this paper uses an existing shopping center as pilot case, which is characterized by a large common multifloor space, which, in turn, gives rise to a significant vertical thermal stratification. This paper explores the importance of MPC parameters to energy efficiency and comfort levels. In addition, it addresses some notable extensions, from economic optimization, which paves the way to real-time pricing techniques, to integration with renewables, to robustness enforcement through Kalman filters, to hybrid control with switching signals mixed with continuous signals. [ABSTRACT FROM PUBLISHER]

In this paper, a four-leg matrix converter is proposed as the power conversion core for aircraft ground power unit (GPU) applications. This structure allows easy management of unbalanced and nonlinear loads with minimal disruption of the power supply operation. A hybrid repetitive-traditional control system is proposed to regulate the output voltage of the GPU. This solution reduces the steady-state tracking error, maintaining fast dynamic characteristics, and increases the stability of the converter compared to conventional approaches. Simulations and experimental results from a 7.5-KW converter prototype are presented to verify the operation of the proposed configuration and to prove the effectiveness of the solution. [ABSTRACT FROM PUBLISHER]

This paper contains a relatively new synthesis method for nonlinear objects, which is named backstepping. This method can be used to obtain the observer structure. This paper presents the structure of the speed observer, which is a new proposition of observer backstepping with additional state variables marked $Z$. The rotor speed can be estimated in three different ways. The first is based on the adaptive approach, the second on the nonadaptive approach, and the third on improvement of the adaptive approach. The stability of the Z-type observer is determined by the Lyapunov stability criteria. Despite this, stability analysis around the machine's working point is undertaken. All the machine tests are prepared in the sensorless control system based on multiscalar variables. The experimental results show the effectiveness of the proposed solution. The squirrel-cage model parameter estimation is not presented in this paper. [ABSTRACT FROM PUBLISHER]

Recently, research concerning electrical machines and drives condition monitoring and fault diagnosis has experienced extraordinarily dynamic activity. The increasing importance of these energy conversion devices and their widespread use in uncountable applications have motivated significant research efforts. This paper presents an analysis of the state of the art in this field. The analyzed contributions were published in most relevant journals and magazines or presented in either specific conferences in the area or more broadly scoped events. [ABSTRACT FROM PUBLISHER]

Modern control systems rely heavily on their sensors for reliable operation. Failure of a sensor could destabilize the system, which could have serious consequences to the system's operations. Therefore, there is a need to detect and accommodate such failures, particularly if the system in question is of a safety critical application. In this paper, a sensor failure detection, identification, and accommodation (SFDIA) scheme is presented. This scheme is based on the fully connected cascade (FCC) neural network (NN) architecture. The NN is trained using the neuron by neuron learning algorithm. This NN architecture is chosen because of its efficiency in terms of the number of neurons and the number of inputs required to solve a problem. The SFDIA scheme considers failures in pitch, roll, and yaw rate gyro sensors of an aircraft. A total of 105 experiments were conducted; out of which, only one went undetected. The SFDIA scheme presented here is efficient, compact, and computationally less expensive, in comparison to schemes using, for example, the popular multilayer perceptron NN. These benefits are inherited from the FCC NN architecture. [ABSTRACT FROM PUBLISHER]