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In this paper, the procedure for designing a sliding-mode controller for maximum power point tracking photovoltaic (PV) applications is proposed. It is applied to a single-ended primary inductor converter, thus to a fourth-order topology, but it can be extended to a wide class of converters suitable for PV applications. The reachability and existence conditions give rise to a number of design inequalities that add to the classical steady-state conditions in order to have the desired closed-loop converter's performances. The superiority of the control technique over the classical tracking methods is analytically demonstrated through the procedure proposed in this paper. The analytical results have been validated by means of both simulations and experiments. [ABSTRACT FROM PUBLISHER]

The main objective of this paper is to provide an efficient computational model for fast and accurate calculation of electromagnetically induced vibrations in electrical machines. Although a three-phase permanent-magnet synchronous machine has been used in this paper, the same methodology can be extended to other types of electric machinery. A brief comparison between the different methods for structural analysis in electrical machines is introduced. The method proposed in this paper uses finite-element analysis in order to extract the impulse responses that are used in calculating the vibration. A field reconstruction method is used for the electromagnetic field analysis. [ABSTRACT FROM PUBLISHER]

Recent advances in lithium-ion battery modeling suggest unequal but controlled and carefully timed charging of individual cells by reduce degradation. This paper compares anode-side film formation for a standard equalization scheme versus unequal charging through switches that are controlled by deterministic dynamic programming (DDP) and DDP-inspired heuristic algorithms. A static map for film growth rate is derived from a first-principles battery model adopted from the electrochemical engineering literature. Using this map, we consider two cells that are connected in parallel via relay switches. The key results are the following: 1) optimal unequal and delayed charging indeed reduces film buildup, and 2) a near-optimal state feedback controller can be designed from the DDP solution and film growth rate convexity properties. The simulation results indicate that the heuristic state feedback controller achieves near optimal performance relative to the DDP solution, with significant reduction in film growth compared to charging both cells equally, for several film growth models. Moreover, the algorithms achieve similar film reduction values on the full electrochemical model. These results correlate with the convexity properties of the film growth map. Hence, this paper demonstrates that unequal charging may indeed reduce film growth, given certain convexity properties exist, lending promise to the concept for improving battery pack life. [ABSTRACT FROM PUBLISHER]

This paper describes the field oriented control of a salient pole wound field synchronous machine in stator flux coordinates. The procedure for derivation of flux linkage equations along any general rotating axes including stator flux axes is given. The stator flux equations are used to identify the cross-coupling occurring between the axes due to saliency in the machine. The coupling terms are canceled as feedforward terms in the generation of references for current controllers to achieve good decoupling during transients. The design of current controller for stator-flux-oriented control is presented. This paper proposes the method of extending rotor flux closed loop observer for sensorless control of wound field synchronous machine. This paper also proposes a new sensorless control by using stator flux closed loop observer and estimation of torque angle using stator current components in stator flux coordinates. Detailed experimental results from a sensorless 15.8 hp salient pole wound field synchronous machine drive are presented to demonstrate the performance of the proposed control strategy from a low speed of 0.8 Hz to 50 Hz. [ABSTRACT FROM AUTHOR]

Multiphase (more than three phases) power electronic converters are required mainly for feeding variable-speed multiphase drive systems. This paper presents one such solution by using a direct ac–ac converter that can be used to supply a nine-phase drive system. The input is a fixed-voltage and fixedfrequency three-phase input, and the output is a variable-voltage and variable-frequency nine-phase output. A simple pulsewidthmodulation technique is developed for the proposed ac–ac converter named as a nonsquare three-to-nine-phase matrixconverter configuration. The developed modulation technique is based on the comparison of a high-frequency carrier signal with the duty ratios. Although the carrier-based scheme is widely employed for the control of back-to-back converters, it has recently been used for controlling a three-to-three-phase matrix converter. This concept is extended in this paper for controlling a threeto-nine-phase matrix converter. With the two techniques that are proposed, one outputs 0.75 of the input magnitude and the other outputs reach 0.762 of the input. This is the maximum value of the output voltage in the linear modulation range that can be achieved in this configuration of the matrix converter. The viability of the proposed control techniques is proved analytically through simulation and an experimental approach. [ABSTRACT FROM PUBLISHER]

This paper presents an adaptive method for tracking the amplitude, phase, and frequency of a time-varying sinusoid in white noise. Although the conventional techniques like adaptive linear elements and discrete or fast Fourier transforms are still widely used in many applications, their accuracy and convergence speed pose serious limitations under sudden supply frequency drift, fundamental amplitude, or phase variations. This paper, therefore, proposes a fast and low-complexity multiobjective Gauss–Newton algorithm for estimating the fundamental phasor and frequency of the power signal instantly and accurately. Further, the learning parameters in the proposed algorithm are tuned iteratively to provide faster convergence and better accuracy. The proposed method can also be extended to include time-varying harmonics and interharmonics mixed with noise of low signal-to-noise ratio with a great degree of accuracy. Numerical and experimental results are presented in support of the effectiveness of the new approach. [ABSTRACT FROM AUTHOR]

A digital sensorless adaptive voltage positioning (SLAVP) control method is presented in this paper in order to realize AVP control without the need for load or inductor current sensing and high-resolution high-speed analog-to-digital converter sampling. The SLAVP control law utilizes the readily available error signal of the conventional voltage-mode closed-loop compensated controller or, in other words, the duty cycle of a dc–dc buck converter in order to realize AVP control. The elimination of the need for high-speed and accurate sensing and sampling of currents using the proposed SLAVP control reduces the size and cost of the digital controller, reduces the power losses associated with current sensing and sampling, and simplifies hardware design. Moreover, the SLAVP control can easily be added to controllers with conventional voltage-mode closed-loop control with minimum size and cost increase, and therefore, SLAVP control can be used for a wide range of applications and not only for high-end applications like powering microprocessors. The theoretical SLAVP control law derivation and analysis and SLAVP controller architecture are presented in this paper and verified by experimental results obtained from a proof-of-concept experimental prototype. [ABSTRACT FROM AUTHOR]

In this paper, a real-time walking trajectory generation method with three-mass models at constant body height for 3-D biped robots is extended for a diagonal walking. By realization of the diagonal walking, the availability is improved. The modeling of this method is more precise than that of conventional real-time walking trajectory generation methods. In this method, the zero-moment point equation of a body is derived, and an analytic solution of a body trajectory at a constant body height in a single support phase is obtained. Because the analytic solution is used, real-time trajectory generation can be realized. In addition, this method has advantages of the body trajectory at the constant body height. The validities are confirmed from simulations of the 2-D walking and an experiment of the 3-D diagonal walking. [ABSTRACT FROM AUTHOR]

This paper presents two new algorithms for real-time calculation of the wheel angles and speeds of gantry tractor modules. In transport mode, the gantry tractor is, in a sense, a snakelike robot with passive joints and active wheels, with each module having autonomous four-wheel drive and four-wheel steering. The algorithms determine the wheel angles and speeds of each module with the prescription that the four wheels will have the same center of curvature, wheel speeds provide cooperative redundancy, and all hitching points follow the same path, thereby eliminating scuffing and minimizing off-tracking. Details of the analytical algorithm for a predetermined path were presented at the 2009 IEEE International Conference on Industrial Technology, together with a simulation for a single module. In this paper, we also present the results of a newly developed numerical algorithm which enables the gantry tractor to be steered online by an operator. We also show, by simulation, that this new numerical algorithm gives a good approximation to analytical solutions. The numerical algorithm is then used to calculate wheel angles and speeds for a three-module tractor with the results depicted graphically as functions of time. [ABSTRACT FROM AUTHOR]

A hybrid generator with a photovoltaic energy conversion system is proposed with supercapacitors and lead-acid batteries in a dc-coupled structure. The objective of this system is to supply the prescribed reactive and active power to the grid. This paper focuses on the strategy, which makes it possible to ensure a high battery state of charge and overcharge security by designing a dedicated local control system. A continuous dynamic model and a control design of the power system studied are proposed in this paper. Simulation and experimental results illustrate the performances obtained. [ABSTRACT FROM AUTHOR]

In this paper, issues related to parameter identification and high-performance control of the drive system with an elastic joint are discussed. After a brief introduction, the mathematical model of the drive and the proposed high-performance control structure are presented. The effect of the location of closed-loop poles and cancellation of zeros of the structure is examined. Then, the mathematical models of the Kalman filters used in this study are presented, and the results of the identification procedure are described. The effectiveness of the proposed structure has been examined under simulation and experimental study. [ABSTRACT FROM PUBLISHER]

In this paper, we consider the friction compensation problem for a class of mechanical systems. The friction behavior is described by a nonlinear dynamical model. Since it is difficult to know the nonlinear parts in the frictional model accurately, two neural networks (NNs) are employed in the proposed intelligent controller. Due to the learning capability of the NNs, the designed NN controller can compensate the effects of the nonlinear friction. Stability of the thus proposed learning control system is guaranteed by a rigid proof. Simulation and experimental results are provided to verify the effectiveness of the proposed intelligent scheme. [ABSTRACT FROM PUBLISHER]

The direct torque control (DTC) technique of permanent-magnet synchronous motors (PMSMs) receives increasing attention due to its advantages in eliminating the current controllers and quicker dynamic response, compared with other motor control algorithms. However, high torque and stator flux ripples remain in the system when using DTC technologies. This means large stator voltage and current harmonic contents exist in the PM motors. Since the variation of motor electromagnetic torque is related to the voltages that are applied to the motor, by analyzing the relationships between stator flux, torque, and voltages, a PMSM torque predictive control scheme is proposed in this paper. In each digital signal processor cycle, the optimized voltage is utilized to reduce torque ripple, and the voltage vector angle is determined by the output of torque and flux hysteresis controllers. The proposed scheme is simulated and experimentally verified. Both simulation and experimental results have shown that low torque ripple and reduced stator current harmonics are achieved by using the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper presents a generic and comprehensive distribution optimal power flow (DOPF) model that can be used by local distribution companies (LDCs) to integrate their distribution system feeders into a Smart Grid. The proposed three-phase DOPF framework incorporates detailed modeling of distribution system components and considers various operating objectives. Phase specific and voltage dependent modeling of customer loads in the three-phase DOPF model allows LDC operators to determine realistic operating strategies that can improve the overall feeder efficiency. The proposed distribution system operation objective is based on the minimization of the energy drawn from the substation while seeking to minimize the number of switching operations of load tap changers and capacitors. A novel method for solving the three-phase DOPF model by transforming the mixed-integer nonlinear programming problem to a nonlinear programming problem is proposed which reduces the computational burden and facilitates its practical implementation and application. Two practical case studies, including a real distribution feeder test case, are presented to demonstrate the features of the proposed methodology. The results illustrate the benefits of the proposed DOPF in terms of reducing energy losses while limiting the number of switching operations. [ABSTRACT FROM AUTHOR]

Machine prognosis is a significant part of condition-based maintenance and intends to monitor and track the time evolution of a fault so that maintenance can be performed or the task can be terminated to avoid a catastrophic failure. A new prognostic method is developed in this paper using adaptive neuro–fuzzy inference systems (ANFISs) and high-order particle filtering. The ANFIS is trained via machine historical failure data. The trained ANFIS and its modeling noise constitute an mth-order hidden Markov model to describe the fault propagation process. The high-order particle filter uses this Markov model to predict the time evolution of the fault indicator in the form of a probability density function. An online update scheme is developed to adapt the Markov model to various machine dynamics quickly. The performance of the proposed method is evaluated by using the testing data from a cracked carrier plate and a faulty bearing. Results show that it outperforms classical condition predictors. [ABSTRACT FROM AUTHOR]

In this paper, a new bridgeless single-ended primary inductance converter power-factor-correction rectifier is introduced. The proposed circuit provides lower conduction losses with reduced components simultaneously. In conventional PFC converters (continuous-conduction-mode boost converter), a voltage loop and a current loop are required for PFC. In the proposed converter, the control circuit is simplified, and no current loop is required while the converter operates in discontinuous conduction mode. Theoretical analysis and simulation results are provided to explain circuit operation. A prototype of the proposed converter is realized, and the results are presented. The measured efficiency shows 1% improvement in comparison to conventional SEPIC rectifier. [ABSTRACT FROM AUTHOR]

Antilock braking systems (ABSs) are usually designed based on controlling the wheel slip ratio so as to maintain each wheel in a presumed stable region. Since the optimal slip ratio (which results in maximum tire–road friction) varies with the type of road, current methods are not efficient in the sense of achieving the shortest possible stopping distance. This paper introduces an efficient ABS, in which the brake commands directly maximize the longitudinal component of tire–road friction at each wheel of the vehicle independently. The tire–road friction is estimated using a torque balance equation at each wheel, and within those equations, real-time estimates of the effective radius of tire are used. A step-by-step algorithm for computing the brake commands that maximize the tire–road friction is also presented. Three challenging braking scenarios were tested using the comprehensive CarSim simulation environment. The results show that, in comparison to conventional ABS, our method significantly reduces the stopping distance and improves the vehicle stability. [ABSTRACT FROM PUBLISHER]

This paper addresses the mean-square and mean-module filtering problems for a linear system with Gaussian white noises. The obtained solutions contain a sliding-mode term, signum of the innovation process. It is shown that the designed sliding-mode mean-square filter generates the mean-square estimate, which has the same minimum estimation-error variance as the best estimate given by the classical Kalman–Bucy filter, although the gain matrices of both filters are different. The designed sliding-mode mean-module filter generates the mean-module estimate, which yields a better value of the mean-module criterion in comparison with the mean-square Kalman–Bucy filter. The theoretical result is complemented with an illustrative example verifying the performance of the designed filters. It is demonstrated that the estimates produced by the designed sliding-mode mean-square filter and the Kalman–Bucy filter yield the same estimation-error variance, and there is an advantage in favor of the designed sliding-mode mean-module filter. [ABSTRACT FROM PUBLISHER]

Multirobot systems represent an enticing area of research with numerous real-world applications. Teams of multiple robots can achieve tasks that are more difficult or even impossible for a single robot, e.g., environment exploration, search and rescue, or surveillance operations. In a previous work, the authors developed a system for the single-operator manual control of a multirobot system. However, such teleoperation systems commonly suffer from inadequate perception of the remote environment. This paper extends the previously presented work by adding a fuzzy force-feedback (FFF) augmentation for the manual control of a multirobot system. The FFF augmentation delivers additional information to the operator. Moreover, it guides the operator toward the smooth control of the robotic group. The force feedback was generated by a system of fuzzy controllers monitoring the state of the multirobot group. The performance of the system was evaluated in a virtual environment, and the recorded forces were explored in various scenarios. The force-feedback augmentation demonstrated the following improvements: 1) operator's increased obstacle awareness and 2) improved maneuvering performance. [ABSTRACT FROM PUBLISHER]

Requirements for system availability for ultrahigh reliability electronic systems such as airborne and space electronic systems are driving the need for advanced health monitoring techniques for the early detection of the onset of damage. Aerospace electronic systems usually face a very harsh environment, requiring them to survive the high strain rates, e.g., during launch and reentry, and thermal environments, including extremely low and high temperatures. Traditional health monitoring methodologies have relied on reactive methods of failure detection often providing little or no insight into the remaining useful life of the system. In this paper, a mathematical approach for the interrogation of the system state under cyclic thermomechanical stresses has been developed for six different lead-free solder alloy systems. Data have been collected for leading indicators of failure for alloy systems, including \Sn3\Ag0.5\Cu, \Sn0.3\Ag0.7\Cu, \Sn1\Ag0.5\Cu, \Sn0.3\Ag0.5\Cu0.1\Bi, \Sn0.2\Ag0.5\Cu0.1\Bi0.1\Ni, and 96.5\Sn3.5\Ag second-level interconnects under the application of cyclic thermomechanical loads. The methodology presented resides in the prefailure space of the system in which no macroindicators such as cracks or delamination exist. Systems subjected to thermomechanical damage have been interrogated for the system state and the computed damage state correlated with the known imposed damage. The approach involves the use of condition monitoring devices which can be interrogated for damage proxies at finite time intervals. The interrogation techniques are based on the derivation of damage proxies and system prior-damage-based nonlinear least square methods, including the Levenberg–Marquardt algorithm. The system's residual life is computed based on residual-life computation algorithms. [ABSTRACT FROM AUTHOR]

This paper provides the comprehensive development procedures and mathematical model of an adjustable speed drive (ASD) for steady-state solutions, transient trajectories, and local stability based on a Floquet multiplier theory. A complete representation of the ASD is employed, which includes the dynamic equation of the dc link capacitor and the detailed models of the diode rectifier and of the pulse width modulated inverter. The power electronic switches are efficiently represented through smooth functions that allow a larger integration step to be used without the loss of precision in the solution. An efficient technique in the time domain for the computation of the periodic steady-state solution of electric systems, including ASDs based on a discrete-exponential-expansion matrix and the Poincaré map, is used. The obtained results are validated against the solutions obtained with an implementation using the Power System Blockset of Simulink and against the response obtained by the measurements from a 1.5-kVA ASD experimental setup system. [ABSTRACT FROM AUTHOR]

Sandia frequency shift (SFS) falls under the active islanding detection methods that rely on frequency drift to detect an islanding condition for inverter-based distributed generation. Active islanding detection methods are commonly tested on constant RLC loads where the load's active power is directly proportional to the square of voltage and is independent on the system frequency. Since the SFS method relies primarily on frequency to detect islanding, the load's active power frequency dependence could have an impact on its performance and the nondetection zone (NDZ). In this paper, the impact of the load's active power frequency dependence on the performance of the SFS method, during an islanding condition, is analyzed. A NDZ model that takes into account the load's frequency dependence parameter is derived mathematically and validated through digital simulation. The results show that the load's frequency dependence has a significant impact on the NDZ of the SFS method and thus is an important factor to consider when designing and testing this method. [ABSTRACT FROM AUTHOR]

A state-space electromyography (EMG) model is developed for continuous motion estimation of human limb in this paper. While the general Hill-based muscle model (HMM) estimates only joint torque from EMG signals in an “open-loop” form, we integrate the forward dynamics of human joint movement into the HMM, and such an extended HMM can be used to estimate the joint motion states directly. EMG features are developed to construct measurement equations for the extended HMM to form a state-space model. With the state-space HMM, a normal closed-loop prediction–correction approach such as the Kalman-type algorithm can be used to estimate the continuous joint movement from EMG signals, where the measurement equation is used to reject model uncertainties and external disturbances. Moreover, we propose a new normalization approach for EMG signals for the purpose of rejecting the dependence of the motion estimation on varying external loads. Comprehensive experiments are conducted on the human elbow joint, and the improvements of the proposed methods are verified by the comparison of the EMG-based estimation and the inertial measurement unit measurements. [ABSTRACT FROM PUBLISHER]

This paper demonstrates a multiplatform hardware-in-the-loop (HIL) approach to observe the operation of a high-speed permanent-magnet synchronous generator coupled with a microturbine in an all-electric-ship power system. The mathematical model of the gas turbine and the dynamic equations of the high-speed generator are implemented in real time on a field-programmable gate array (FPGA). This real-time simulation interfaces with hardware via a serial peripheral interface to a supervisory digital signal processor (DSP) of a three-phase voltage source inverter. The inverter output load is virtually emulated in the FPGA using received hardware measurements from the DSP. A user input interface is introduced using dSPACE on a personal computer to acquire data and adjust the speed reference of the generator system through a serial communication interface to the DSP. The real-time simulation and HIL experimental setup are validated in a scaled medium voltage dc ship power system. [ABSTRACT FROM AUTHOR]

AC induction motors and permanent magnet synchronous drives became very popular for motion control applications due to their simple and reliable construction. Sensorless drive control is required in many applications to reduce drive production costs. While many approaches to magnetic flux, rotor speed, or other quantities needed to control electrical machine were proposed, conditions under which these quantities can be estimated are not often sufficiently investigated. In this paper, induction machine and permanent-magnet-synchronous-machine drive state observability analysis is presented, together with conditions allowing reliable rotor speed and position estimation. A method based on the nonlinear dynamical system state observability theory is proposed, resulting in a unified approach to the ac drive observability analysis. [ABSTRACT FROM PUBLISHER]

This paper considers achieving the minimum total harmonic distortion (THD) or frequency-weighted THD (WTHD) of the staircase-modulated output voltage of single-phase multilevel inverters, with or without elimination of the lowest order harmonics. The minimal THD values, together with the corresponding step angles and dc voltage source ratios, have been obtained for the 5-, 7-, 9-, 11-, and 13-level cases; accounting for the device voltage drops when the load is resistive or is moderately inductive is described. Similarly, the minimal WTHD values, together with the corresponding step angles and dc source voltage ratios, have been obtained for the five-, seven-, and nine-level waveform cases. The results show that requiring harmonic elimination leads to larger W/THD than the minimum W/THD that can be achieved without this requirement. Furthermore, a 13-level waveform is needed to attain a voltage THD less than 5%, and a nine-level waveform is needed to attain a WTHD less than 0.5%. Experimental measurements are presented as verification of the analytical results. [ABSTRACT FROM PUBLISHER]

This paper proposes a deterministic particle swarm optimization to improve the maximum power point tracking (MPPT) capability for photovoltaic system under partial shading condition. The main idea is to remove the random number in the accelerations factor of the conventional PSO velocity equation. Additionally, the maximum change in velocity is restricted to a particular value, which is determined based on the critical study of P–V characteristics during partial shading. Advantages of the method include: 1) consistent solution is achieved despite a small number of particles, 2) only one parameter, i.e., the inertia weight, needs to be tuned, and 3) the MPPT structure is much simpler compared to the conventional PSO. To evaluate the idea, the algorithm is implemented on a buck-boost converter and compared to the conventional hill climbing (HC) MPPT method. Simulation results indicate that the proposed method outperforms the HC method in terms of global peak tracking speed and accuracy under various partial shading conditions. Furthermore, it is tested using the measured data of a tropical cloudy day, which includes rapid movement of the passing clouds and partial shading. Despite the wide fluctuations in array power, the average efficiency for the 10-h test profile reaches 99.5%. [ABSTRACT FROM PUBLISHER]

Permanent magnet linear motors are a type of linear motors that are generally used in precision motion control applications. However, the position of motor is easily disturbed by external force, disturbance, and variation in parameters of plant. Therefore, the construction of the high-precision linear motion system is a difficult task. This paper implements a modified disturbance observer and compensator, which includes a novel variable gain, to overcome the effects of unknown parameters of the motor, to minimize the effect of the disturbance, and to reduce the response time of the disturbance. This compensated linear motor is further controlled by the internal model reference control algorithm so that the position of the motor can be tracked with expected response precisely. The authors conducted the experiments and verified the feasibility of the high-precision positioning control. Compared with the case of normal disturbance compensator, the experimental results also illustrate the improvements of the novel variable gain, which reduces the response time toward the command signal and the external disturbance. [ABSTRACT FROM PUBLISHER]

This paper presents an inverter parallel system with a corresponding networked control strategy for parallel operations. In this system, all the modules have the same circuit configuration and two control loops: the inner control loop is used for output voltage regulation, and the outer loop is used for accurate power-sharing regulation formulated by a weighted power function with networked data. The method with low-bandwidth communication is employed to achieve the superior load-sharing accuracy compared to droop-only scheme. In addition, good robustness can be obtained in the case of communication failure. A state-space model has been developed to describe the dynamics of the active and reactive power of the networked parallel-connected inverter system. We also present the methodologies of predicting stability for system with time delay and data drop-out due to the use of network-in-the-loop of this networked parallel inverter system. Experimental results are also shown to validate the effectiveness and advantages of the proposed networked parallel inverter system. [ABSTRACT FROM AUTHOR]

This paper presents a state equation model of a single-phase pulsewidth modulation inverter connected to the grid, using frequency–active power and voltage–reactive power droops, including an extra phase shift loop. The influence of the control parameters on the system's behavior can be studied using the proposed state equation model, which was obtained from the small-signal analysis. The model's results are compared with numerical simulations of the nonlinear system to verify their accuracy. Comparisons are also made with experimental data reported in the literature. [ABSTRACT FROM PUBLISHER]

This paper reviews the convective heat transfer within the air gap of both cylindrical and disk geometry rotating electrical machines, including worked examples relevant to fractional horsepower electrical machines. Thermal analysis of electrical machines is important because torque density is limited by maximum temperature. Knowledge of surface convective heat transfer coefficients is necessary for accurate thermal modeling, for example, using lumped parameter models. There exists a wide body of relevant literature, but much of it has traditionally been in other application areas, dominated by mechanical engineers, such as gas turbine design. Particular attention is therefore given to the explanation of the relevant nondimensional parameters and to the presentation of measured convective heat transfer correlations for a wide variety of situations from laminar to turbulent flow at small and large gap sizes for both radial-flux and axial-flux electrical machines. [ABSTRACT FROM PUBLISHER]

This paper investigates the sampled-data control problem for spacecraft relative positional holding with limited thrust and thrust nonlinearity. The relative dynamic model is established based on the Clohessy–Wiltshire equations. Sector nonlinearity is employed to describe the nonlinear behavior of the chaser's thruster. The relative position holding problem is regarded as a sampled-data output tracking control problem, and the disturbance attenuation for the closed-loop system is considered. By a Lyapunov approach, the controller design is cast into a convex optimization problem. Simulation results show the effectiveness and advantage of the proposed controller design method. [ABSTRACT FROM PUBLISHER]

Advanced distribution management system (DMS), an evolution of supervisory control and data acquisition obtained by extending its working principles from transmission to distribution, is the brain of a smart grid. Advanced DMS assesses smart functions in the distribution system and is also responsible for assessing control functions such as reactive dispatch, voltage regulation, contingency analysis, capability maximization, or line switching. Optimal power flow (OPF)-based tools can be suitably adapted to the requirements of smart distribution network and be employed in an advanced DMS framework. In this paper, the authors present a methodology for unbalanced three-phase OPF (TOPF) for DMS in a smart grid. In the formulation of the TOPF, control variables of the optimization problem are actual active load demand and reactive power outputs of microgenerators. The TOPF is based on a quasi-Newton method and makes use of an open-source three-phase unbalanced distribution load flow. Test results are presented on the IEEE 123-bus Radial Distribution Feeder test case. [ABSTRACT FROM AUTHOR]

This paper presents FuSnap, a fuzzy-logic-based controller that monitors and controls the snapshot process of a logical storage volume in a disk array. As disks do not linearly respond to the arrival rate of user accesses, FuSnap makes use of fuzzy logic as the means to achieve better control of their response time. The goal of the FuSnap controller is to reduce the response time caused by the copy-on-writes (CoWs) that occur during the snapping of a storage logical volume. The FuSnap controller, based on the response time of user accesses, makes the decision on whether to proceed with a CoW or a redirect-on-write when a source logical volume is being copied to a snapshot logical volume. The benefits of FuSnap approach are twofold. First, significant reductions in response time of user requests are obtained with the FuSnap approach over the traditional CoW snap approach. Second, these reductions in response time make the point-in-time copy of data a process less disruptive for database users. FuSnap was verified with two setups using Hewlett-Packard UniX workstations, one setup with eight and the other with 32 disks. [ABSTRACT FROM AUTHOR]

Multilevel inverters introduce harmonics to the network besides their remarkable advantages. Total harmonic distortion (THD) is one of the most important indexes to evaluate the harmonic contents of waveforms. The conventional method of line-voltage THD calculation gives approximate answers, because high-order harmonics are ignored. In this paper, an analytical algebraic method based on formulating the line-voltage THD of multilevel inverters with unequal dc sources is presented. This method, which is general and applicable to each number of switching angles, is implemented to a five-level inverter with staircase waveform as a case study. The implementing process of this method can be easily repeated for each number of levels. The accuracy of the proposed method is illustrated in comparison with the approximate method. Some advantages of the extracted formulas of line-voltage THD are simplicity and rapidity in calculations, considering all harmonics and the possibility of finding optimal switching angles analytically. Experimental results are presented to validate the theory. [ABSTRACT FROM PUBLISHER]

This paper presents a new three-phase step-up dc–dc converter with a three-phase high-frequency (HF) isolation transformer in an average current-mode controlled closed loop. This converter was developed for industrial applications where the dc input voltage is lower than the output voltage, for instance, in installations fed by battery units, photovoltaic arrays, or fuel cell systems. The converter's main characteristics are reduced input ripple current, step-up voltage, HF transformer, reduced output-voltage ripple due to three-pulse output current, and the presence of only three active switches connected to the same reference, this being a main advantage of this converter. By means of a specific switch modulation, the converter allows two operational regions, each one depending upon the number of switches in overlapping conditions—if there are two switches, it is called R2 region, and if there are three switches, it is called R3 region. An average current-mode control strategy is applied to input-current and output-voltage regulation. Theoretical expressions and experimental results are presented for a 6.8-kW prototype, operating in the R2 region, and for a 3.4-kW prototype, operating in the R3 region, both in continuous conduction mode. [ABSTRACT FROM PUBLISHER]

This paper presents a mathematical dynamic model of single-phase four-quadrant (4Q) converters employed at the input stage onboard high-speed trains. A new stability analysis capable of considering the time-variant nature of the system for the correct tuning of the feedback proportional-integral (PI) controller has been implemented. In particular, the innovation regards the application of a current-controlled modulation technique instead of the traditional PWM control currently used in high power traction converters. A dedicated model of a real converter installed onboard Italian high-speed trains has also been implemented in order to simulate its behavior and validate the theoretical analysis. Finally, a scaled-down prototype has been developed. [ABSTRACT FROM AUTHOR]

Wireless power technology offers the promise of cutting the last cord, allowing users to seamlessly recharge mobile devices as easily as data are transmitted through the air. Initial work on the use of magnetically coupled resonators for this purpose has shown promising results. We present new analysis that yields critical insight into the design of practical systems, including the introduction of key figures of merit that can be used to compare systems with vastly different geometries and operating conditions. A circuit model is presented along with a derivation of key system concepts, such as frequency splitting, the maximum operating distance (critical coupling), and the behavior of the system as it becomes undercoupled. This theoretical model is validated against measured data and shows an excellent average coefficient of determination (R^2) of 0.9875. An adaptive frequency tuning technique is demonstrated, which compensates for efficiency variations encountered when the transmitter-to-receiver distance and/or orientation are varied. The method demonstrated in this paper allows a fixed-load receiver to be moved to nearly any position and/or orientation within the range of the transmitter and still achieve a near-constant efficiency of over 70% for a range of 0–70 cm. [ABSTRACT FROM AUTHOR]

Artificial neural network models have been successfully applied to solve a job-shop scheduling problem (JSSP) known as a Nonpolynomial (NP-complete) constraint satisfaction problem. Our main contribution is an improvement of the algorithm proposed in the literature. It consists in using a procedure optimizing the initial value of the starting time. The aim is to speed a Hopfield Neural Network (HNN) and therefore reduce the number of searching cycles. This new heuristic provides several advantages; mainly to improve the searching speed of an optimal or near optimal solution of a deterministic JSSP using HNN and reduce the makespan. Simulation results of the proposed method have been performed on various benchmarks and compared with current algorithms such as genetic algorithm, constraint satisfaction adaptive neural networks, simulated annealing, threshold accepting, flood method, and priority rules such as shortest processing time (SPT) to mention a few. As the simulation results show, and Brandts algorithm, combined with the proposed heuristic method, is efficient with respect to the resolution speed, quality of the solution, and the reduction of the computation time. [ABSTRACT FROM AUTHOR]

To measure the angular position of motors, robot joints, etc., an absolute magnetic rotary position sensor is developed, which possesses small-size, light, robust, and easy-to-integrate properties. The sensor consists of two inductors, i.e., a code disc and a signal processing part. Both of the two inductors are embedded with a big planar spiral copper coil and four smaller copper coils by employing microelectromechanical system (MEMS) technology, and there are two circles of regular copper sheets listing on the surface of the code disc. In addition, mathematical analyses of the inductor structure as well as the relationships of position and dimension among the coils and the copper sheet are addressed. Finite-element simulation results demonstrate that one group of the optimal sine and cosine signals can be generated by each inductor. Then, the absolute position measurement method is validated by a mathematical method. Finally, experiments are performed on the high-speed and the low-speed testing platforms to assess effectiveness and accuracy of the sensor. [ABSTRACT FROM PUBLISHER]

As an emerging technique with a promising application prospect, the device-free localization (DFL) technique has drawn considerable attention due to its ability of realizing wireless localization without the need of equipping the target with any device. The DFL technique detects the shadowed links and realizes localization with the received signal strength (RSS) measurements of these links. However, one major disadvantage of the DFL technique is that the RSS signal is too sensitive, and a slight variation of the environment will cause the variation of RSS measurements, which incurs the misjudgment of shadowed links and degradation of localization performance. To solve this problem, a robust DFL scheme based on differential RSS is proposed. The scheme utilizes the novel differential RSS to judge whether a link is shadowed, which not only eliminates the need of acquiring reference RSS measurements but also overcomes the negative effect incurred by the environment. Meanwhile, an outlier detection scheme is presented to filter out the outlier links that are far away from the target. We present the observation model of the shadowed links and incorporate it into the particle filter framework to realize location estimation robustly. Experimental results demonstrate the outstanding performance of the proposed scheme. [ABSTRACT FROM PUBLISHER]

A genre of low-cost and high-performance sensors for measuring the irradiation angle is proposed via a working mechanism of the physical design and mathematical modeling. A dexterous mechatronic design, together with a gray-box modeling approach, was used to deploy the photovoltaic and cosine effects of sensors in a way that could measure the irradiation angle accurately. Two pairs of identical photodiodes, mounted symmetrically on four facets of an inverted pyramid, yielded currents under the uniform irradiation that would map to the irradiation angle mathematically. A sensor prototype was calibrated in a controlled indoor environment via a celebrated test bed and also tested outdoor under direct solar irradiation, where the manufacturing and assembly errors were compensated for by the gray-box modeling approach. It was shown that the sensor prototype had advantages over others in terms of the synergy of accurate angle measurement, low cost, compact size, sensitivity to light, and wide sensing range. [ABSTRACT FROM PUBLISHER]

Active du/dt is a new output-filtering method to mitigate motor overvoltages. The inverter pulse pattern edges are broken down into narrower pulses, which control the filter LC circuit. This results in an output voltage that does not have to exhibit the overshoot typically seen in common LC circuits in output-filtering applications. Furthermore, the shape of the output-voltage edge has properties well suited for output-filtering applications. An appropriate filter rise time is selected according to the motor-cable length to eliminate the motor overvoltage. The basis of the active du/dt method is discussed in brief. Considerations on the application of the active du/dt filtering in electric drives are presented together with simulations and experimental data to verify the potential of the method. [ABSTRACT FROM AUTHOR]

A simple equivalent-circuit model is developed for a wireless energy-transfer system via coupled magnetic resonances, and a practical design method is also provided. Node equations for the resonance system are built with the method, expanding on the equations for a transformer, and the optimum distances of the coils in the system are derived analytically for optimum coupling coefficients for high transfer efficiency. In order to calculate the frequency characteristics for a lossy system, the equivalent model is established at an electric-design automation tool. The model parameters of the actual system are extracted, and the modeling results are compared with measurements. Through the developed model, it is seen that the system can transfer power over a midrange of a few meters and that impedance matching is important to achieve high efficiency. [ABSTRACT FROM AUTHOR]