Integrating renewable resources, such as wind and solar into the existing power system, has introduced new challenges due to their rapid fluctuations, which tends to decrease the reliability of the grid. One method to cope with this uncertainty and variability in generation is managing the demand side through direct load control. Thermostatically controlled appliances can play a significant role for this purpose; however, the system operator requires a reliable estimation about the magnitude of the load and how much it can be shifted. This article presents a novel methodology to formulate and forecast the control capacity of a population of thermostatically controlled appliances. In addition to that, this methodology can provide an estimation on how long the system can follow a desired level of power consumption and how the aggregated load would change once the controller stops (i.e., the payback). The performance of the proposed method was evaluated using a numerical simulator of a population of the loads. Simulation results show that the proposed method can provide a reliable estimation about controllability of the load in terms of minimum and maximum achievable load, the time interval that it can hold the load at a certain level, and how the uncontrolled load would behave after the control period.
This account details the design and construction of a sophisticated tracking wheel for the accelerated aging of polymer insulators by subjecting them to surface contamination and high voltage. Automated control of wet-dry cycles is achieved by means of a computer-controlled lift mechanism that operates in tandem with the rotation. The applied voltage is continuously variable and can accommodate insulators of mixed lengths. The design incorporates a fail-safe control system that automates the selected test cycle, provides an intuitive user interface, and integrates multiple safety measures. This is achieved by implementing a programmable logic controller with digital and analog inputs and outputs. An associated ladder logic program automates the actuation of electromechanical hardware while also processing the inputs provided from control hardware, such as limit switches, optical encoders, variable frequency drives, and sensors. A touch-screen human interface module provides feedback and allows the user a means of input. Programmed fault detection, flood sensors, and a trapped key system increase the level of user safety and provide environmental and infrastructure protection.
In this article, a threshold-based induction motor fault diagnosis method is proposed using the measured stator current signal. A 0.25-HP three-phase squirrel-cage induction motor fed directly online is tested in the laboratory with various single- and multielectrical faults under six different loading conditions. The discrete wavelet transform (DWT) is chosen as the signal processing technique for the measured stator currents. The threshold and energy values at each decomposition level of the DWT processing results are evaluated. Threshold values appear to be more consistent than energy values at different measured data windows, and thus, the threshold at the decomposition level d8 is chosen as a fault indicator. Curve fitting equations are developed to calculate threshold values for the motor loadings that were not tested in experiments. The suitability using threshold values for induction motor fault diagnosis is further validated using two probabilistic methods, the correlation analysis and the confidence interval estimation.
Over the past several decades, there has been a constant increase in the use of unmanned aircraft systems (UASs). Hence, there has also been a growth in the number of control algorithms to service many applications embodied by these vehicles. Initially, UASs were made popular by the military for reconnaissance, intelligence, surveillance, and target acquisition (RISTA) applications. Nowadays, UASs are used for everything from crop surveys to tourism. Nowhere is this more evident than with a multi-rotor unmanned aerial vehicle (UAV). This paper presents a survey of control methods for multi-rotor systems, namely quadrotors. In doing so, we hope to visualize a clear path to what additional capabilities might be needed in the future. In our examination, we review many of the notable research organizations and their efforts to expand the utility of multi-rotor aircraft. We also summarize the basic literature definitions and control strategies for autonomous quadrotors.
This paper deals with the computation of all proportional-integral (PI)-based pitch controllers which achieve the desired frequency-domain specifications, namely, gain and phase margins (GPMs) of a large wind turbine (LWT) with communication delays. An efficient graphical method based on extracting the boundaries of stability regions in PI controller parameter space having user-defined GPMs has been employed to determine GPM-based stability regions for a wide range of time delays. The theoretical region boundaries are validated by using a powerful numerical method known as the quasi-polynomial mapping-based root finder (QPmR) and time-domain simulations. Results indicate that the proposed scheme gives an improved dynamic response compared to the recently developed scheme based on stability only for the pitch control of LWTs with communication delays.
We present a parametric framework (UFleSe) with a user-friendly interface having a search engine that enables regular users (without the need of neither technical nor theoretical knowledge) to define their fuzzy concepts, rules, similarity relations, synonyms, antonyms, and personalizing their definitions for different users, and to link them with the crisp database fields for performing flexible, expressive queries in a language close to natural language. It works over multiple modern and conventional data formats, such as JSON, SQL, Prolog, CSV, XLS, and XLSX. We present the syntax involved in the construction of our various flexible searching criteria and their personalizations. Furthermore, we present the architecture of this novel system that combines fuzzy, crisp data, and similarity relations in its queries to return constructive answers ordered by a degree of searching criteria satisfaction (truth-value between 0 and 1). Finally, we include a comparative analysis of different fuzzy querying systems here, and we provide various experiments, to show the system behavior, performance, efficiency, and scalability as well.
Many noncoherent distributed strategies for cooperative sensor networks that do not require channel knowledge at any antenna to overcome the overhead involved in channel estimation are lately suggested; however, these strategies suffer from low system performance in terms of bit error rate (BER) and a comparably high decoding complexity. Differential beamforming strategies have recently been proposed to overcome these problems; however, they are implemented using the four-phase protocol. Thus, we propose a new strategy based on the three-phase protocol to increase the symbol rate. By doing this, a significant improvement can be achieved in the overall system performance. Hence, in this article, a new bidirectional differential beamforming strategy is suggested: 1) to be applied on the three-phase protocol instead of the four-phase protocol; 2) to be applicable for a decentralized wireless sensor network using single-antenna sensors distributed randomly between the communicating base stations; 3) to enjoy low decoding complexity; and 4) to improve the network performance in terms of BER by maximizing the received signal-to-noise ratio at the receiving base station without requiring channel knowledge at any antenna in the whole network. From our simulation results, the proposed strategy shows a substantially improved BER performance compared with the current state-of-the-art ones.
The use of cloud Infrastructure as a Service (IaaS) for enterprise applications is at an all-time high and is charted to continue growing to approximately 73% by 2022. IaaS suffers from several security concerns, such as hypervisor hijacking, virtual machine (VM) hopping, and account hijacking. With such a large percentage of enterprise traffic on the cloud, a strong security framework is demanded. To secure IaaS, this article proposes a software-defined perimeter (SDP) as a solution. SDP provides a logical perimeter to restrict access to services with a layer of authentication and authorization to allow. Only authorized clients may connect to services hidden by SDP gateways. SDP is implemented and verified in an AWS cloud environment. Port scanning is used to verify SDP behavior as well. The results demonstrate the SDP’s ability to “darken” services behind a gateway. The performance of SDP against a denial-of-service (DoS) attack is demonstrated in a local environment. The test results demonstrate that SDP is indeed capable of resisting DoS attacks while allowing legitimate user traffic even under the duration of the attack. These results lead to a discussion on future research for SDP in IaaS.
In induction motors, the leakage reactance values are obtained from the motor short circuit operation experiment. However, these values do not give clear results for different geometries. For this reason, taking into the parameters of the slot geometry accounts for determining the stator and rotor leakage reactance values that are important in terms of obtaining more accurate results. This paper has investigated the stator slot permeance values of nine different stator slot structures commonly used in industrial type of three-phase squirrel cage induction motors for obtaining the best starting torque. The stator inductance and leakage reactance values were calculated for each stator slot structure. The change of starting torque of the induction motor has been analyzed by using the MATLAB code. As a result of the analysis, the stator slot structure, which gives the best starting torque, has been obtained. It has been also shown that a 16% improvement can be achieved by changing the stator slot structure at the starting torque. This increase in the starting torque will provide a great advantage for the motor’s acceleration versus a heavy load.
This article introduces a concept to extend the base speed of a switched reluctance motor (SRM) from the perspective of the motor’s design. Conventionally, designs prioritize a high saliency of SRM in order to produce more torque with the same current. However, the speed range is limited in the conventional design. The back EMF is the key factor that restricts the speed of the SRM from further increasing due to its strong reaction to the phase terminal voltage applied, which is especially severe at high-speed operation. Therefore, in this article, the design of an SRM with a lower inductance slope is proposed. The reduction of the motor’s saliency in the proposed idea can effectively diminish the back EMF; thus an extended base speed and wider constant torque range can be achieved. Comparative simulation results from the conventionally designed motor and the motor designed by the proposed idea are given, which demonstrate that the base speed is enhanced and the current control can be maintained at a higher speed in the proposed idea.
A four-element frequency reconfigurable and pattern diverse multiple-input–multiple-output (MIMO) antenna array for fifth-generation relay node applications is presented to operate in LTE bands 42 (3400–3600 MHz), 43 (3600–3800 MHz), and 46 (5150–5925 MHz). A planar microstrip line-fed monopole antenna is utilized as the MIMO element. The antenna relies on fluidic reconfiguration mechanism to either serve LTE bands 42/43 or 46. It incorporates a substrate milled channel beneath each monopole arm to hold distilled water. The water in the channel perturbs the $E$ -field distribution in the vicinity of the antenna arm and modifies the effective permittivity of the dielectric medium. To realize pattern diversity, adjacent elements are placed orthogonal to each other. Measured prototype exhibits a total active reflection coefficient $|{\text{TARC}}|$ and $|S_{11} |\leq -10$ dB for the high band when the channel is vacant (case 1) and the low band when filled with water (case 2), while minimum isolation is above 19.6 dB. The peak measured gain is ~4.6 and ~2.8 dBi, while the worst case envelope correlation coefficient (ECC) is ~0.004 and ~0.016 for cases 1 and 2, respectively. It measures 82.4 $\times$ 82.4 mm2 and was fabricated on a 1.52-mm-thick substrate of $\epsilon_{r}$ = 3.55.
This article contributes to the evaluation of the performance and the precision of the IEC 61850 protocol implementation for real-time simulation. The importance of this study stems from two facts. First, the simulation is a required stage of any design process including that of an IEC 61850 model of utilities, which may include an automation system from two or more vendors. Second, verification of the vendor's claim to be compliant with a specific edition of IEC 61850 relies in part on the simulation. We validate the interfacing of the IEC 61850 generic object-oriented substation event (GOOSE) and sampled value (SV) packets through the I/O modules of the simulation environment. In addition, this protocol interfacing is applied to validate a distance protection relay model using the IEC 61850 modules of GOOSEs and SVs in the HYPERSIM real-time simulator taking advantage of an SGI parallel supercomputer. The distance protection relay is implemented in Simulink, tested and validated with MATLAB Simscape Power Systems and imported into HYPERSIM via the HYPERLINK module. The simulation result has been evaluated in terms of reliability and time delay which plays an important role for the communication and cyber systems in smart grids. This real-time simulation setup is valuable for prototyping, analysis, and validation of control algorithms compliant with IEC 61850.
The framework for designing a slow-light waveguide structure with Conical Swiss Roll Metamaterial at THz frequencies have been carried out. In the earliest work, theoretical backgrounds based on Maxwell’s equations have been developed for anisotropic single-negative permeability slab waveguides and anisotropic Metamaterial slab waveguides. Subsequently, simulation results fulfilled by MATLAB programming tool verify extremely-low group velocities in the aforementioned slab waveguides in THz regime frequency. A volumetric Conical Swiss Roll Metamaterial has been proposed as a practical achievement for slow-light waveguides. Dispersion characteristics of the electromagnetic waves in the proposed Conical Swiss Roll Metamaterial have been investigated using CST simulation tool in THz frequencies. Furthermore, two-dimensional dispersion diagram drawn by CST and MATLAB validates highlyelectromagnetics field concentration as well as the presence of backward waves in the Conical Swiss Roll configuration.
Turbulent fluid flow data are often 4-D, spatially and temporally complex, and require specific techniques for visualization. Common visualization techniques neglect the temporal aspect of this data, limiting the ability to convey feature motion, or offering the user a complicated visualization. To remedy this, we present an approach-evolution surfaces-focused on the spatiotemporal rendering of user-selected flow features (i.e., vortices). By abstracting the spatial representation of these features, the approach renders their spatiotemporal behavior with reduced visual complexity. The behavior of vortex features is presented as surfaces, with textures indicating properties of motion and evolution events (e.g., bifurcation and amalgamation) represented by the surface topology. We evaluated the approach on two data sets generated from empirical measurement and computational simulation (Re = 28 000 and Re = 1200, respectively). Our approach's focus on handling evolution events makes it capable of visualizing higher Reynolds number (Re) flows than other surface-based techniques. This approach has been assessed by fluid dynamicists to assert the validity for flow analysis. Evolution surfaces offer a compact visualization of spatiotemporal vortex behaviors, opening potential avenues for exploration and analysis of fluid flows.
Digital images are found in several sizes and are easily displayed on a computer screen using techniques that can reduce their dimensions. Moreover, algorithms are used to process images to perform several tasks, for instance, detection of people. Recently, gigapixel images emerged, providing a huge amount of data; however, algorithms for people detection have been usually tested only on regular size images. This paper presents an impact analysis of the resolution reduction in the detection of people in gigapixel images. People detectors were trained with the INRIA and CALTECH data sets and results show that, although gigapixel images provide a huge false positive rate, the resolution reduction significantly decreases the number of bounding boxes and false positives, however, increasing the rate of missing people.
A microstrip circular patch antenna with frequency and polarization reconfigurability using liquid metal is presented. The antenna has a C-shaped slot cut at the center of the patch and reconfigurability is achieved using two putty containers and liquid metal to switch between four different states. Linear polarization (LP) is observed at 5.83 GHz when there is no liquid metal inside the containers. Depositing two liquid metal droplets in the containers yields circular polarization (CP) at 6 GHz. The right-hand CP (RHCP) is obtained when the right-most container is filled, and the left-hand CP (LHCP) is obtained when the leftmost container is filled with the liquid metal. When all containers are filled, LP is observed at 6.15 GHz. For the LP case, the antenna has a measured gain of 2.68 dB when all containers are filled and a measured gain of 3 dB when the containers are empty, and the axial ratios (ARs) are 19.65 dB (filled containers) and 23.74 dB (empty containers). When the LHCP is activated, the gain is 2.44 dB and the AR is 0.54 dB at 6 GHz. For RHCP, the gain is 2.37 dB and the AR is 1.5 dB at 6 GHz.
This article develops a novel average torque control (ATC) scheme for switched reluctance (SR) motor on the basis of a brand-new microstep flux–current locus controller. The proposed ATC is based on the calculation of the average torque from the converted mechanical energy that can be illustrated as an enclosed area in a flux–current plane. It has the superior advantage that it is able to control the average torque over any arbitrary small-angle intervals, whereas the conventional ATC can control only the average torque for a whole stroke. In order to realize the proposed ATC, a flux–current locus controller, which consists of a hybrid flux controller and current controller as well as involve the microstep process, is introduced in this article. The flux–current locus of the energy conversion loop is controlled for the first time in the literature. With the locus controller, it is possible to achieve a better energy conversion ratio and the ATC. In order to verify both the proposed locus control method and the ATC for SR motor, detailed simulation results and discussion are provided.
This article presents an effective on-chip power analysis attack countermeasure based on a new CMOS self-decoupling battery cell system that uses a self-decoupling circuit. The self-decoupling circuit dynamically controls an on-chip virtual power supply point, $V_{\mathrm {ddv}}$ , that can be used to power security-sensitive modules. The circuit automatically decouples an on-chip CMOS battery cell from powering a sensitive module when its voltage level reaches a designed minimum threshold level $V_{\mathrm {dd-min}}$ and connects it for a very short charging cycle to the chip’s main voltage supply, $V_{\mathrm {dd}}$ . The charging cycles for the experiments presented in this article are less than 10 ns and are designed to support the CMOS battery cell size and the minimum designed threshold voltage level $V_{\mathrm {dd-min}}$ . Simulation results of test designs implemented in the 45-nm CMOS technology process show that the proposed countermeasure is efficient when used with battery cell sizes that can power the protected cryptographic module for more than ten data operation cycles before recharging. In addition, using the on-chip self-decoupling battery cell system allows for power consumption savings within the protected module of up to 43 % due to the dynamic voltage scaling generated at the virtual power supply point.
This paper introduces an obstacle-aware fuzzy-based scheme for the localization of wireless chargers in wireless sensor networks (WSNs), which aims to deploy chargers in both fixed and/or multiple duty-cycled networks. A power harvesting model is proposed that considers the obstacle penetration loss in the harvested power from multiple chargers. We take advantage of the fuzzy control system (FCS) scheme to gain prior knowledge about the distribution pattern of the nodes. The simulation results confirm that deploying chargers based on this scheme decreases the required number of chargers, in comparison with the nonfuzzy algorithms by up to 59.6% in multiduty-cycled and 34.4% in fixed duty-cycled scenarios, in the best cases.
A custom hardware coprocessor is described to improve the efficiency of applications using arithmetic in the Galois field GF(2) and the extension fields GF( $2^{m}$ ). The evaluation of such processor enhancements requires a variety of test exercises based on GF(2) arithmetic. Various test procedures are presented, which leverage the properties of finite fields to exercise the GF(2) arithmetic coprocessor incorporated with a 32-bit field-programmable gate array (FPGA)-based soft processor (Nios II). Up to 60 times speed improvement was achieved in typical calculations using the coprocessor. Résumé —Un coprocesseur personnalisé a été décrit pour améliorer l’efficacité des applications utilisant l’arithmétique en extension de Galois GF(2) et l’extension de corps GF(2m). L’évaluation des améliorations d’un tel processeur nécessite une variété d’exercices tests qui se basent sur l’arithmétique de GF(2). De nombreux tests de procédures ont été présentés, ils exploitent les propriétés des corps finis afin d’exercer le coprocesseur arithmétique GF(2). Ce dernier a été incorporé sur une matrice de portes programmables par l’utilisateur (FPGA) à 32 bits en se basant sur un processeur embarqué (Nios II). La vitesse des calculs a été améliorée jusqu’à 60 fois en utilisant le processeur.
