Search

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 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 proposes an interleaved buck converter (IBC) with continuous input current, extremely low output current ripple, low switching losses, and improved step-down conversion ratio. Unlike the conventional IBC, the proposed converter has a continuous input current, and its output current ripple is extremely low. The proposed converter has a lower voltage stress in comparison to the conventional IBC and can also provide a high step-down ratio, which makes it a proper choice for high-power applications where a nonisolated step-down converter with low output current ripple and continuous input current is required. Also, the proposed converter can provide current sharing between two interleaved modules without using additional current-sharing control method. All of these benefits are obtained without any additional stress on the circuit components. A prototype converter with 200-V input and 24-V–10-A output is implemented to verify the theoretical analysis. Operational principles and experimental results are presented in this paper. [ABSTRACT FROM PUBLISHER]

The development of advanced techniques for process monitoring and fault diagnosis using both model-based and data-driven approaches has led to many practical applications. One issue that has not been considered in such applications is the ability to deal with key performance indicators (KPIs) that are only sporadically measured and with significant time delay. Therefore, in this paper, the data-driven design of diagnostic-observer-based process monitoring schemes is extended to include the ability to detect changes given infrequently measured KPIs. The extended diagnostic observer is shown to be stable and hence able to converge to the true value. The proposed method is tested using both Monte Carlo simulations and the Tennessee-Eastman problem. It is shown that although time delay and sampling time increase the detection delay, the overall effect can be mitigated by using a soft sensor. Furthermore, it is shown that the results are not strongly dependent on the sampling time, but do depend on the time delay. Therefore, the proposed soft-sensor-based monitoring scheme can efficiently detect faults even in the absence of direct process information. [ABSTRACT FROM PUBLISHER]

The realm of hardware-in-the-loop simulation resorts to field-programmable gate arrays to achieve time steps below 1 \mu\s . Such low time steps are of importance for the aerospace and automotive industries, where power converters have their switching frequencies in the 10- to 200-kHz range. This paper proposes a network tearing technique that allows subsets of switches to be treated independently, alleviates embedded memory requirements, and reduces the computational burden. An iterative algorithm is used to determine the state of naturally commutated switches, thus offering a realistic model of the power converter, independently of its operation mode or topology. A Gauss-Jordan processing unit is implemented to solve interface voltages/currents from the torn circuit. Custom floating-point operators are used to ensure good accuracy, high-frequency operation, and low computational latency. A neutral-point-clamped converter case study is presented to demonstrate the effectiveness of the method. Simulation results are validated against a reference model at a 750-ns time step and a 30-kHz sine pulsewidth modulation switching frequency. [ABSTRACT FROM PUBLISHER]

In this paper, a novel bias-reduction method is proposed to analytically express and reduce the bias arising in sensor network localization problems, thereby improving the localization accuracy. The proposed bias-reduction method mixes Taylor series and a maximum-likelihood estimate and leads to an easily calculated analytical bias expression in terms of a known maximum-likelihood cost function. In contrast to existing contributions, this paper considers a sensor network as a whole when the bias is investigated by introducing the geometric structure of the sensor network into the proposed bias-reduction method via the rigidity matrix, a concept drawn from graph theory. The maximum-likelihood cost function is related to the rigidity matrix resulting in the final analytical expression of localization bias in terms of the rigidity matrix. Another important contribution of this paper is that, in addition to the presented simulation results, experimental results obtained by using a wireless localization system, which is developed based on reconfigurable software-defined radios (SDRs), are also provided to verify the performance of the proposed bias-reduction method. Both the simulation and experimental results demonstrate that the proposed method can reduce the bias, thereby improving the localization accuracy in different scenarios. [ABSTRACT FROM PUBLISHER]

This paper proposes an analytical procedure for computation of all pairs of valid switching angles used in pattern generation in five-level H-bridge cascaded inverters. The proposed procedure eliminates harmonic components from inverter output voltage and, for each harmonic, returns the exact boundaries of all valid modulation index intervals. Due to its simple mathematical formulation, it can be easily implemented in real time using a digital signal processor or a field-programmable gate array. In this paper, after a detailed description of the method, simulation and experimental results demonstrate the high quality of achievable results. [ABSTRACT FROM PUBLISHER]

In past years, LLC resonant converters have become a mainstream topology for dc–dc power conversion due to their advantages, such as the superior efficiency obtained with the soft switching of MOSFETs. In order to further improve the efficiency of the converter, synchronous rectification (SR) can be implemented as an alternative for diode rectification. As a result, the vast majority of the literature related to this field of study presents different LLC SR control algorithms, which aim to improve the operation of the rectification. Unlike prior work on SR controllers, this paper contributes to the area of power loss estimation using rectifier current equations (RCE). The developed method based on time-domain analysis of SR currents provides a new analytical framework to characterize the behavior of SR. Implications in SR power losses of different time delays are investigated using the developed loss estimation method. In addition, different converter design parameters, such as choice of inductance ratio, can be analyzed. The RCE captures the true discontinuous and complex behavior of SR, which is often oversimplified by the conventional first-harmonic approximation (FHA). As a result, the proposed method facilitates the design of LLC resonant converters and provides increased precision in SR power loss estimation when compared to FHA, and in a considerably faster fashion when compared with precise yet computationally intensive simulation software. This paper is validated with simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper is devoted to an autonomous approach to a moving ship for unmanned vehicles. The problem is introduced and formulated first. Cooperation between the vehicle and the ship is needed, such that the moving ship to be approached is set to move at a constant speed along a straight line or a circle. Hence, an approaching algorithm based on 3-D path generation is proposed. The 3-D vehicle trajectory produced by the path generation realizes smooth transition from the initial pose to the final pose with geometric constraints. The final poses the unmanned vehicle and the ship's reach simultaneously are analyzed and obtained based on 3-D path generation. The related parameters for autonomous navigation of an unmanned vehicle are discussed according to the straight line or the circle that the ship sails along. The approaching algorithm is sequentially summarized. The simulations are conducted, and the results show the effectiveness and real-time performance of the proposed method. [ABSTRACT FROM PUBLISHER]

Low-bandwidth communication channels are used to support the information exchange between a microgrid centralized controller and local controllers in the secondary frequency control of an islanded microgrid. However, the impact of the inherent time delay in these communication channels on the microgrid performance has not been taken into account when the secondary frequency controller is designed. This paper investigates the effect of the communication delays on the secondary frequency control of an islanded microgrid with multiple distributed generators. A small-signal model-based method is introduced for the microgrid to find delay margins below which the microgrid can remain stable. By performing a series of trial studies, the relationships between secondary frequency control gains and delay margins are obtained. A gain scheduling approach is also proposed to compensate the effect of the communication delay on the secondary frequency control. Results from the Canadian urban distribution system have verified that communication delays can adversely affect the microgrid secondary frequency control, and the proposed gain scheduling approach can improve the robustness of the microgrid secondary frequency controller to communication delays. [ABSTRACT FROM PUBLISHER]

This paper offers a model-based fault detection and isolation (FDI) scheme for a rudder servo system (RSS) that manages ship navigation. Inherent nonlinearities and unknown external disturbances present great challenges in applying FDI technologies to RSS in practice. This paper presents the derivation of the state equations and commonly encountered fault types of RSS from physical laws, and the design of five nonlinear unknown input observers (NUIOs) capable of eliminating the influences of unknown disturbance while detecting and isolating faults. In the NUIOs, no boundary assumption is made on the disturbance, and their parameter matrices are obtained using a linear-matrix-inequality method. Along with an algorithm that programs the logic rules for FDI, the model-based FDI scheme has been implemented on an actual RSS test rig for validating the RSS model and experimentally evaluating it in a real-world environment; both actuator and sensor faults are considered. Based on experimental tests, an adaptive threshold method is introduced to improve decision making and hence effectively eliminate false alarms. Experimental results show that the model-based scheme is efficient and can be used for online FDI. [ABSTRACT FROM PUBLISHER]

This paper studies different circulating current references for the modular multilevel converter. The circulating current references are obtained from the instantaneous values of the output current and modulation signal of the phase leg. Therefore, the determination of the amplitude and phase of the output current is not needed, which is a significant improvement compared to other methods such as those based on injecting specific harmonics in the circulating currents. Among the different methods studied in this paper, a new method is introduced, which is able to reduce the capacitor voltage ripples compared to the other methods. A closed-loop control is also proposed which is able to track the circulating current references. With the discussed methods, the average values of the capacitor voltages are maintained at their reference while the voltage ripples are kept low. Experimental results are presented to demonstrate the effectiveness of the proposed and discussed methods. [ABSTRACT FROM PUBLISHER]

This paper presents a dynamic-model-based control scheme for the balancing and velocity control of a unicycle robot. Unicycle robot motion consists of a pitch that is controlled by an in-wheel motor and a roll that is controlled by a reaction wheel pendulum. The unicycle robot lacks an actuator for yaw-axis control, which makes the derivation of the dynamics relatively simple although it may limit the motion control. The Euler–Lagrange equation is applied to derive the dynamic equations of the unicycle robot to implement dynamic speed control. To achieve real-time speed control, a sliding-mode control and a nonzero set-point linear quadratic regulator (LQR) are utilized to guarantee stability while maintaining the desired speed-tracking performance. In the roll controller, a sigmoid-function-based sliding-mode controller has been adopted to minimize switching-function chattering. An LQR controller has been implemented for pitch control to drive the unicycle robot to follow the desired velocity trajectory in real time using the state variables of pitch angle, angular velocity, wheel angle, and angular velocity. The control performance of the two control systems using a single dynamic model has been experimentally demonstrated. [ABSTRACT FROM PUBLISHER]

This paper presents a voltage-source converter (VSC) topology for high-power applications. This topology combines three three-phase converters with isolated dc buses. The proposed topology can be implemented by using two-level or multilevel three-phase converters. In this paper, three three-level neutral-point-clamped (3L-NPC) converters have been combined. Two zero-sequence blocking transformers (ZSBTs) are used to interconnect the three converters. In order to validate the good performance of the proposed VSC topology, two modulation techniques are implemented: phase-shifted carrier pulsewidth modulation (PSCPWM) and selective harmonic elimination (SHE) modulation. The VSC topology has been simulated in the simulation tool Saber, and the results have been validated experimentally in a test bench of 60 kVA. [ABSTRACT FROM PUBLISHER]

The maximum power point (MPP) tracking function allows one to extract the maximum power from the photovoltaic (PV) system in any operating condition. The perturb and observe technique is one of the mainly used algorithms aimed at this function. Its performances depend on the values of the two design parameters, which are the amplitude and the frequency of the perturbations that it applies in identifying the position of the MPP. In this paper, a method for the online optimization of the perturbation period is presented. It is based on the identification of the whole system, including the PV source and the dc/dc converter controlling it. The system impulse and frequency responses are evaluated by using the cross-correlation method. Such a technique, as well as the tracking algorithm, is effectively implemented by using a field-programmable gate array, and it is validated by means of simulation and experimental results. [ABSTRACT FROM PUBLISHER]

The main hypothesis proposed in this paper is that by controlling the harmonic and zero-sequence components of the current in nonsinusoidal permanent-magnet synchronous generators (PMGs), additional energy can be obtained, thereby increasing the machine power density without increasing the Joule effect losses. Two different strategies are proposed for three- and four-wire topologies; therefore, four different cases are analyzed. The strategies consist in controlling the PMG stator currents, following a function that depends on the waveform of the back electromotive force (EMF). The current function is obtained from the instantaneous reactive power theory. An experimental system was built to validate the proposal. Experimental results prove that it is possible to increase power in a tested PMG by 7% using the four-wire topology in comparison with the conventional block commutation and same losses. Higher power gain can be obtained for machines with almost rectangular-shaped EMF waveforms. [ABSTRACT FROM PUBLISHER]

In this paper, a discrete-time neural network for solving convex quadratic programming (QP) problems in constrained model predictive control (MPC) technology is investigated and implemented on a digital signal processor (DSP) device. This makes it possible to apply MPC technology to local control for high-dimensional multiple-input–multiple-output systems. The convergence issue of the discrete-time neural network is first studied. By choosing a proper error function, a sufficient condition is obtained under which the neural network converges to the exact optimal solution globally. This is the theoretical basis of this paper. An integrated hardware and software design method to implement the neural network on a DSP chip as a universal QP solver is then developed. With the QP solver handling the computational tasks in MPC problems, a general DSP-based MPC controller is achieved. A prototype system is built on a TMDSEVM6678L DSP development board. It is then applied to an air-separation-unit system and achieves satisfactory control performance. This verifies the effectiveness of the whole design. [ABSTRACT FROM PUBLISHER]

In this paper, a real-time implementation of selective harmonic elimination pulsewidth modulation (SHEPWM) using generalized Hopfield neural network (GHNN) as applied to the single-phase inverter is designed and discussed. Finding the location of the switching instants in the case of SHEPWM involves the solution of a set of nonlinear algebraic transcendental equations. The problem is redrafted as an optimization problem, and it is solved by using GHNN. Though, in principle, the $n$ number of harmonics can be eliminated using the presented methodology, this paper tries for the case of the elimination of the 5th-, 7th-, 11th-, and 13th-order harmonics while retaining the desired fundamental. An energy function is formulated for this problem and the set of ordinary differential equations (ODEs) describing the behavior of GHNN is obtained. A program in KEIL C was developed to solve these systems of ODEs by the Runge–Kutta fourth-order method to give the switching instants for continuously varying modulation indexes $(M)$. A MATLAB simulation was carried out, and an experimental setup was also constructed in order to validate the simulated results. The fast Fourier transform analysis of the simulated output voltage waveform and the experimental output voltage waveform confirms the effectiveness of the proposed method. Hence, the proposed method proves that it is much applicable in the industrial applications by virtue of its suitability in real-time applications. [ABSTRACT FROM PUBLISHER]

In this paper, a new method to calculate the five parameters of the single-diode model of a photovoltaic cell or panel is presented. This new method takes into account the intrinsic properties of the model equation and the technique of linear least-squares fitting; so, the computational complexity and costs are very low. Moreover, the proposed method, named two-step linear least-squares method, is able to work absolutely blindly with any kind of I–V curve. It does not need initial guesses at all and, consequently, it is not necessary to know previously any information of any parameter. The proposed method provides the parameters of the single-diode model just using the coordinates of $N$ points $(N\ge 5)$ of the I–V curve. The results provided by this method in a first stage have the same order of accuracy of the best documented methods in the field of parameters extraction, but, furthermore, in a second stage, the best accuracy documented until now is obtained in two important case studies usually used in the literature as well as in a large-scale I–V curve repository with more than one million of curves. [ABSTRACT FROM PUBLISHER]

Dual-phase lock-in amplifiers (LIAs) are designed to extract information (amplitude and phase) from signals buried in high noise levels. In spite of their popularity, their use has been traditionally limited to input sinusoidal waves with symmetric power supplies. This paper presents an algorithm that enables single-supply analog LIAs to properly process input square waves. Formed by linear equations, its computational implementation is much simpler than that of the traditional sinusoidal algorithm. Moreover, applied to battery-operated microcontrolled systems where square signals can be generated by the embedded microcontroller, it presents intrinsic advantages such as simplicity, versatility, and reduction in power and size. Experimental results validate the proposed algorithm, confirming its enormous possibilities in sensing applications. [ABSTRACT FROM PUBLISHER]

This paper presents the new implementation of the finite control states set model predictive control (FS-MPC) applied to three-level four-leg flying capacitor converter (FCC) operating as a shunt active power filter (SAPF). The three main issues regarding the algorithm development are described and the solutions are proposed. The first is addressed to modeling of the four-wire system, which for simplification is based on wire-to-wire voltage equations. The second relates to the control of FCC by MPC, i.e., a proper interpretation of the FCC switching states and control of flying capacitor (FC) voltages, which was moved from the prediction loop. Finally, the system restriction regarding undesirable switching states’ transitions is explained and the solution is presented. The control performance was tested in the simulation model in MATLAB–Simulink and validated experimentally by measurements on the 10-kVA FCC laboratory setup. [ABSTRACT FROM PUBLISHER]

Permanent-magnet (PM) brushless direct current (BLDC) drives are utilized in a variety of applications because of their inherent features and would be even more utilized if their torque performance could be improved. Indeed, when supplied with square-wave currents, the torque–speed characteristic undergoes a drop at high speeds, and a significant torque ripple arises at both low and high speeds due to the commutation phenomena. In this paper, the sinusoidal current supply of the PM BLDC motors is investigated in depth, and an analytical formulation of the torque–speed characteristic, the torque ripple, and the base speed for such a supply are found. Based on the resulting equations, a thorough convenience analysis of the sinusoidal current supply is carried out with respect to the square-wave current in the presence of the commutation phenomena, which is hereafter termed as the real square-wave current supply. Simulation and experimental tests for a study case are given to corroborate the theoretical results. Generation of the sinusoidal current references using Hall sensors is also discussed. [ABSTRACT FROM PUBLISHER]

The lithium titanate battery, which uses Li 4Ti 5O 12 (LTO) as its anode instead of graphite, is a promising candidate for fast charging and power assist vehicular applications due to its attractive battery performance in rate characteristics and chemical stability. Unfortunately, commonly used battery models, including a large number of enhanced electrical models, become problematic when describing current–voltage characteristics of lithium titanate batteries. In this paper, a novel Butler–Volmer equation-based electric model is employed to outline unique phenomena induced by changing rates for high-power lithium titanate batteries. The robustness of the proposed model for three types of lithium titanate batteries under varying loading conditions, including galvanostatic test and Federal Urban Dynamic Schedule test, is evaluated and compared against experimental data. The experimental results of three types of lithium titanate batteries with common anode materials but differentiated cathode materials show good agreement with the model estimation results with maximum voltage errors below 2%. [ABSTRACT FROM PUBLISHER]

In this paper, a new modified single-switch single-ended primary inductor converter (MS2-SEPIC)-based high step-up dc–dc converter is presented. The proposed topology uses the coupled-inductor (CL) technique and a voltage tripler rectifier, which results in a high voltage gain for the converter. Here, the switching loss has been reduced significantly owing to the quasi-resonance operation of the circuit created by the leakage inductance of the CL along with circuit capacitors. The operational principles and steady-state analysis are discussed. Experimental results based on a 100 W laboratory prototype verify the validity of theoretical analysis. [ABSTRACT FROM AUTHOR]

The in-phase bias modulation (IPBM) mode of scanning ion conductance microscopy (SICM), which has advantages of both the dc mode and the traditional ac mode, is immune to low-frequency external electronic interference and potential drift while maintaining a high scanning speed. However, the IPBM mode still suffers from a low-signal-to-noise ratio (SNR). In this paper, we propose a capacitance compensation (CC) method to solve the problem in the IPBM mode of SICM. After CC, the signal level is significantly increased while the noise level remains unchanged. The increased SNR not only improves the image quality but also allows the system to work at a higher modulation frequency, thus increasing potential for fast scan. Experimental results verify the effectiveness of the IPBM mode of SICM with CC. [ABSTRACT FROM PUBLISHER]

To effectively reject the influence of the low damping property of permanent magnetic bearings and improve the twist motion stability, this paper presents a novel equivalent damping control strategy. First, the relationship between the restoring torque and the radial translation of permanent magnetic rings is pointed out through finite-element analysis. The analysis indicates that the restoring torque increases with the radial translation of the rotor off its origin. Then, the radial translation variation rule is proposed, which can provide equivalent damping for the twist motion. Subsequently, a bang–bang controller is designed enlightened by the variation rule. Moreover, the stability of the bang–bang control is verified using energy consumption arguments, which is similar to the Lyapunov method. Finally, simulation and experimental results are presented to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper deals with the discrete-time modeling of induction motors (IMs) by means of a variational integrator. A Lagrangian is first formulated for the IM, where the corresponding discrete Lagrangian is derived based on the one-point quadrature rule integration method (in this case, the variational integrator is known as symplectic Euler). Then, a discrete action principle is applied, which guarantees the optimum path in a discrete-time setting. The forcing and dissipation are added by using the discrete Lagrange d'Alembert principle. Finally, discrete-time update rules are obtained for IMs. Then, theoretic properties such as relative degree and steady state are studied for the continuous-time symplectic Euler and explicit Euler models. Simulations are carried out for different sampling periods, where results are compared with a discrete-time model obtained with the classical explicit Euler method. It is put in evidence that the symplectic Euler model approximates better the IM dynamics than the model obtained with the classical Euler method. [ABSTRACT FROM PUBLISHER]

The performance of dc–dc converters plays a vital role in the exploitation of renewable energy sources such as solar and fuel cell (FC). This paper demonstrates the feasibility of using the input/output (I/O) magnetically coupled interleaved buck–boost converter, improving the conventional interleaved cascaded buck–boost converter in FC applications. While keeping the same step-up/step-down voltage transfer ratio, the proposed topology facilitates operating conditions with its nonpulsating I/O currents and high efficiency using interleaved technique and reducing switches' voltage stresses, respectively. The steady-state operation of the converter is analyzed based on the state-space-averaging method and supported with simulation results. The prototype setup of 360-W and 36-V output voltage for an FC with a brand of “FCgen 1020ACS” Ballard Power Systems, Inc. was implemented. Experimental results are presented to verify the theoretical expected merits of the converter, including high efficiency and nonpulsating I/O currents. [ABSTRACT FROM PUBLISHER]

Modular multilevel converters offer several benefits, such as high scalability and power quality, which are particularly advantageous for high-voltage dc transmission systems. However, the control of such converters is very challenging due to the number of control objectives to be achieved simultaneously. The input and output currents must be controlled at their own references, and these references must be properly generated in order to keep the average capacitor voltage constant. The circulating current can be controlled either to minimize losses or to reduce capacitor voltage ripple. Additionally, the capacitor voltage must be kept balanced among cells during the converter operation. In this paper, a model with four independent dynamical components of the arm currents, which also considers the effect of ac and dc systems, is proposed. The proposed model facilitates the dynamical analysis of currents and simplifies the design and implementation of current controllers. Analysis of the proposed current model and experimental results, which confirm the performance of the designed controllers, is shown. [ABSTRACT FROM PUBLISHER]

In this paper, selective harmonic mitigation (SHM) and selective harmonic elimination (SHE) modulation techniques have been combined to produce appropriate pulses for a four-leg three-level neutral point clamped (NPC) inverter. In the proposed hybrid method, the SHM technique is applied to phase legs in order to mitigate non-triplen harmonics (fifth, seventh, $\ldots$) , and the fourth leg is controlled by the SHE principle to eliminate important low-order triplen harmonics (third, ninth, $\ldots$) completely. In this context, it is demonstrated that using SHM instead of an SHE modulator for phase legs leads to a reduced vast range of harmonic orders in the NPC output voltage, significantly. Moreover, it is proved that the presented hybrid switching technique has the ability of dc-bus capacitor voltage balancing, inherently. Furthermore, analyses are performed to calculate the dc-bus capacitances accurately to show 5% voltage ripple acceptably. Simulation and experimental results validate a good dynamic performance of the proposed hybrid modulation technique in firing the NPC inverter switches to generate low-harmonic voltage waveforms supplying balanced and unbalanced loads while balancing the dc capacitor voltages in a four-wire network with small dc-link capacitors. [ABSTRACT FROM PUBLISHER]

Robust measurement of the specular weld pool surface can help better understand the complex welding processes and provide feedback for robotic welding. The strong arc light and the specular surface of the weld pool make it difficult for the direct sensing measurement. In this paper, a novel imaging and measurement system is proposed, and it makes use of the strong penetrability of the laser to avoid the interference of arc light and obtain the surface information of the weld pool. By intercepting the reflection of a projected laser pattern twice, the proposed system gives a closed-form solution for each reflected ray and a closed-form solution for the corresponding point on the weld pool surface. The weld pool surface can be thus reconstructed by one-shot structured light projection. To increase the robustness of the measurement system, the least deformation principle is proposed to rectify the coefficient errors of the computed plane equation. Finally, a sequence of 3-D weld pools is reconstructed and compared with state-of-art literature. The comparison verifies that our method is significantly better than all the other methods in measuring the 3-D weld pool shapes. [ABSTRACT FROM PUBLISHER]

This paper presents a novel approach on diode model parameter identification from the $I$– $V$ characteristics of photovoltaic panels. Other than the prevailing methodology of solving a group of nonlinear equations from a few points on the $I$– $V$ curve, the proposed methodology views the diode model as the equivalent output of a dynamic system. From this new viewpoint, diode model parameters are linked to the transfer function (after Laplace transform) of the same dynamic system whose parameters are then identified by a simple integral-based linear square. The indoor flash test shows the accuracy and effectiveness of the proposed method, and outdoor module testing shows its ability of online monitoring and diagnostics. Comparisons to the methods of Lambert W function and evolution algorithms are also included. [ABSTRACT FROM PUBLISHER]

Parameter mismatches seriously impact the stability and the rotor-speed accuracy in sensorless induction motor drives, particularly in low speed. To deal with the parameter sensitivity of the drive system with an adaptive full-order observer (AFO), this paper proposes a new unified parameter-sensitive equation that could accurately show the estimated rotor-speed error caused by all four kinds of parameter mismatches—rotor resistance, stator resistance, mutual inductance, and leakage inductance—with arbitrary feedback gains. With the proposed equation, the parameter sensitivity in the full operating region can be directly calculated, avoiding lots of simulations or experiments usually used in traditional analysis. Thus, the equation contributes to select a suitable feedback gains for a robust AFO. Moreover, based on steady-state operating point analysis, a feasible condition is proposed for judging the drive system's stability when parameter mismatches exist. The validity of the proposed analysis will be confirmed by simulation study and experimental results. [ABSTRACT FROM PUBLISHER]

The particle filter (PF) provides a kind of novel technique for estimating the hidden states of the nonlinear and/or non-Gaussian systems. However, the general PF always suffers from the particle impoverishment problem, which can lead to the misleading state estimation results. To cope with this problem, a modified particle filter, i.e., intelligent particle filter (IPF), is proposed in this paper. It is inspired from the genetic algorithm. The particle impoverishment in general PF mainly results from the poverty of particle diversity. In IPF, the genetic-operators-based strategy is designed to further improve the particle diversity. It should be pointed out that the general PF is a special case of the proposed IPF with the specified parameters. Two experiment examples show that IPF mitigates particle impoverishment and provides more accurate state estimation results compared with the general PF. Finally, the proposed IPF is implemented for real-time fault detection on a three-tank system, and the results are satisfactory. [ABSTRACT FROM PUBLISHER]

In this paper, the problem of fault diagnosis of a wind farm is addressed using interval nonlinear parameter-varying (NLPV) parity equations. Fault detection is based on the use of parity equations assuming unknown but bounded description of the noise and modeling errors. The fault detection test is based on checking the consistency between the measurements and the model, by finding if the formers are inside the interval prediction bounds. The fault isolation algorithm is based on analyzing the observed fault signatures online and matching them with the theoretical ones obtained using structural analysis. Finally, the proposed approach is tested using the wind farm benchmark proposed in the context of the wind farm fault-detection-and-isolation/fault-tolerant-control competition. [ABSTRACT FROM PUBLISHER]

In the field weakening region, the voltage is utilized to the maximum to minimize the current amplitude. In this paper, the hexagonal voltage limit is considered to increase the voltage and to decrease the current, as a result to reduce the copper loss. At first, an intersection between the hexagonal voltage limit and torque curve was found. Because the intersection lies on the boundary of the hexagon, the equations of the sides of the hexagon were derived. Since the hexagonal voltage limit rotates in the synchronous reference frame, they are a function of the rotor position. Finally, the voltage angle was calculated from the intersection. To reduce the torque ripple, $d$-axis current feedback was added to the voltage angle. In the simulation and experiment results, an increase of voltage and a decrease of current were observed. In addition, an improvement of the motor and inverter efficiencies was also achieved. [ABSTRACT FROM PUBLISHER]

Low-order odd current harmonics arise in practical multiphase drives due to machine and converter nonlinear behavior (e.g., deadtime and flux saturation). If the windings are distributed, some harmonics cause torque ripple, whereas others produce losses. The latter is aggravated by the small impedance in the no-torque subspaces. Current harmonics can be compensated without steady-state error by proportional–integral controllers in multiple synchronous frames (SFs); however, a heavy computational load is required. In three-phase systems, the computational burden of this multiple SF (MSF) scheme is often avoided by implementing instead resonant controllers (RCs) tuned at the harmonics that are multiples of six in an SF rotating with the fundamental frequency. A similar structure has been proposed for nonlinearities compensation in asymmetrical six-phase machines. This paper extends this multiple RC (MRC) strategy to symmetrical machines of any phase number. The optimum frequencies for the RCs and for the SF in each plane, so that the number of RCs is minimized, are established. Then, the computational load of the resulting generic MRC scheme is assessed and compared with that of the MSF structure. The conditions in which the former is particularly preferable over the latter are identified. Experimental results are provided. [ABSTRACT FROM PUBLISHER]

Automotive embedded electronic systems have been increasing in power and complexity and, therefore, more advanced power electronic converters are necessary in these vehicles. Several dual-voltage (42 V/14 V) bidirectional converter architectures have been proposed for automotive systems in recent years. However, most of them have low efficiency or are based in series and parallel configurations with large number of semiconductors and magnetics devices. Therefore, in this paper, we propose a bidirectional high-efficiency converter with lower number of components. This converter was created by merging a switched-capacitor converter and a conventional bidirectional converter, resulting in a hybrid topology. The voltage across the semiconductors of the proposed converter is equal to half of the highest voltage source value. Furthermore, the topology is composed of only one inductor to control the power flow between the two voltage sources. To verify all the mentioned features, a prototype was implemented experimentally, reaching a maximum efficiency of 97.5%. [ABSTRACT FROM PUBLISHER]

Navigation accuracy of an inertial navigation system can be significantly enhanced by rotating inertial measurement unit with gimbals. Therefore, nonorthogonal angles of gimbals, which are coupled into the navigation error during rotation, should be calibrated and compensated effectively. In this paper, the relationship model of nonorthogonal angles and navigation error is established. Then, the calibration scheme and observation equation during gimbals rotation is proposed. Proved by a piecewise constant system method, all of the error parameters are observable and can be estimated by an extended Kalman filter. Experimental results show that compared with the traditional method, the proposed method can substantially reduce velocity error on static base. Moreover, the position accuracy of long-term navigation under moving base is also significantly increased. [ABSTRACT FROM PUBLISHER]

This paper addresses the stability and tracking control problem of a quadrotor unmanned flying robot vehicle in the presence of modeling error and disturbance uncertainty. The input algorithms are designed for autonomous flight control with the help of an energy function. Adaptation laws are designed to learn and compensate the modeling error and external disturbance uncertainties. Lyapunov theorem shows that the proposed algorithms can guarantee asymptotic stability and tracking of the linear and angular motion of a quadrotor vehicle. Compared with the existing results, the proposed adaptive algorithm does not require an a priori known bound of the modeling errors and disturbance uncertainty. To illustrate the theoretical argument, experimental results on a commercial quadrotor vehicle are presented. [ABSTRACT FROM PUBLISHER]

One of the formation schemes in multirobot systems is named as the leader–follower scheme. Dynamic equations based on the scheme are formulated for multirobot systems with uncertainties by Defoort et al. ( IEEE Trans. Ind. Electron. vol. 55, no. 11, pp. 3944–3953, Nov. 2008). This paper focuses on the equations, clarifies their drawbacks, and revisits the modeling of the leader–follower formation scheme for multirobot systems with uncertainties. [ABSTRACT FROM PUBLISHER]

In this paper, a prevalent type of zero-voltage- transition bidirectional converters is analyzed with the inclusion of the reverse recovery effect of the diodes. The main drawback of this type is missing the soft-switching condition of the main switches at operating duty cycles smaller than 0.5. As a result, soft-switching condition would be lost in one of the bidirectional converter operating modes (forward or reverse modes) since the duty cycles of the forward and reverse modes are complement of each other. Analysis shows that the rectifying diode reverse recovery would assist in providing the soft-switching condition for the duty cycles below 0.5, which is done by a proper design of the snubber capacitor and with no limitation on the rectifying diode current rate at turn-off. Hence, the problems associated with the soft-switching range and the reverse recovery of the rectifying diode are solved simultaneously, and soft-switching condition for both operating modes of the bidirectional converter is achieved with no extra auxiliary components and no complex control. The theoretical analysis for a bidirectional buck and boost converter is presented in detail, and the validity of the theoretical analysis is justified using the experimental results of a 250-W 135- to 200-V prototype converter. [ABSTRACT FROM PUBLISHER]

The real-time reentry trajectory and attitude coordination control for a reusable launch vehicle (RLV) is a very important and challenging problem. There are many aspects that make the research appealing, such as being able to autonomously replan a new trajectory onboard when the landing site is changed. In order to achieve the goal, an integrated guidance and control architecture is proposed in this paper. First, the offline reentry trajectory is designed based on adaptive Gauss pseudospectral method. Then, the obtained trajectory is used as the initial value guess for real-time reentry trajectory optimization. As a result, the pseudospectral-based optimal feedback reentry guidance is achieved via successive real-time optimal open-loop control which ensures that the guidance system has sufficient robustness for initial reentry perturbations. Furthermore, a multitime scale smooth second-order sliding-mode controller with disturbance observer is proposed to ensure the finite-time reentry attitude tracking despite the model parameter uncertainties and unknown external disturbances. Finally, two representative simulation tests are carried out to demonstrate the effectiveness of the proposed integrated guidance and control architecture for six-degree-of-freedom RLV. [ABSTRACT FROM PUBLISHER]

In this paper, an analytic method for generating a unit step pattern using a center of mass (COM) constraint is presented. Using a unit step pattern with the COM position constrained in the supporting polygon at the end of each step, a robot can have a stationary time interval between steps to control and stabilize its posture. The walking pattern is based on the linear inverted pendulum model. Assuming radical zero moment point (ZMP) trajectories, a simple solution form of the COM trajectories is formulated. Three types of case studies are presented for an analytic solution, which is based on different constraints on ZMP references, COM, and time differences. The unknown parameters of the COM trajectories in the solution form are formulated for the different cases. One of the cases was tested for long-stride walking with the DRC-HUBO robot developed at the Korea Advanced Institute of Science and Technology for the Defense Advanced Research Project Agency Robotics Challenge. Experiments of long-stride walking on bricks were successfully performed using the unit step pattern with several previous controllers of HUBO. [ABSTRACT FROM PUBLISHER]

In this paper, we review relevant problems in the modeling of dc–dc converters with switched capacitors. We study several approaches that overcome the exposed modeling difficulties, addressing ideal and nonideal cases and using dynamic equations that are valid in a large-signal domain. [ABSTRACT FROM PUBLISHER]

In this paper, a novel control strategy to naturally balance a hybrid converter is presented for medium-voltage induction motor drive applications. Fundamental current of the motor is produced by a three-level quasi-square-wave converter. Several single-phase full-bridge converters are connected in series with this quasi-square-wave converter to eliminate harmonic voltages from the net output voltage of this hybrid converter. Various novel modulation strategies for these series cells are proposed. These lead to a naturally regulated dc-bus voltage of series cells. These also optimize the number of series cells required. Variable fundamental voltage and frequency control of induction motor is adopted with a constant dc-bus voltage of the three-level quasi-square-wave converter. Experimental results are also produced here to validate the proposed modulation strategies for induction motor drives using low-voltage protomodel. Based on the aforementioned, a 2.2-kV induction motor drive has been built, and results are also produced in this paper. [ABSTRACT FROM PUBLISHER]

In this paper, a new structure for cascade multilevel converters is presented. The proposed structure is based on a cascaded connection of submultilevel converters. The proposed cascade structure can generate a large number of levels with reduced numbers of insulated-gate bipolar transistors, gate drivers, antiparallel diodes, dc voltage sources, and blocked voltage by switches. For the proposed cascade converter, a new algorithm to determine dc source values is presented. In addition, the optimal structures are presented for different goals. The suggested structure is compared with conventional cascade and other topologies. The performance and operation of the suggested submultilevel and cascade structures is verified by experimental and simulation results. Validation of the analytical conclusions is done using MATLAB/Simulink software. [ABSTRACT FROM PUBLISHER]

This paper presents the design and implementation of a field-programmable gate array (FPGA)-based architecture for the speed control of sensorless permanent-magnet synchronous motor (PMSM) drives. For the reduction of computation resources, as well as accuracy improvement in the rotor position estimation, a parallel reduced-order extended Kalman filter (EKF) is proposed in this work. Compared with an EKF, the system order is reduced and the iteration process is greatly simplified, resulting in significant savings of resource utility, while maintaining high estimation performance. The whole control system includes a current-control-and-coordinate-transformation unit, a proportional–integral (PI) speed controller, and other accessory modules, all implemented in a single FPGA chip. A hardware description language is adopted to describe advantageous features of the proposed control system. Moreover, the finite-state-machine method is applied with the purpose to reduce logic elements used in the FPGA chip. The validity of the approach is verified through simulation based on the Modelsim/Simulink cosimulation method. Finally, experimental results are obtained on an FPGA platform with an inverter-fed PMSM to show the feasibility and effectiveness of the proposed system-on-programmable-chip for PMSM drives. [ABSTRACT FROM PUBLISHER]

In this paper, the applicability of the well-known single-diode equivalent circuit to modeling amorphous silicon photovoltaic modules is questioned. It is shown that, unlike in mono- and polycrystalline modules, all of the equivalent circuit parameters are irradiation dependent. This dependence may be derived from either manufacturer-provided or measured $I$– $V$ curves for different irradiation levels. In order to extract the equivalent circuit parameters, the suggested approach combines numerical solution of two transcendental and two regular algebraic equation systems with single-parameter fitting procedure. Two additional parameters are introduced to describe temperature dependence of photocurrent and diode reverse saturation current. As result, a set of seven parameters is obtained, comprehensively describing the panel performance for arbitrary ambient conditions. It is shown that characteristic curves obtained using the proposed approach match well the manufacturer-provided data for various values of temperature and irradiation. [ABSTRACT FROM PUBLISHER]

Visual saliency aims to predict the attentional gaze of observers viewing a scene, and it is thus highly demanded for tone mapping of high dynamic range (HDR) images. In this paper, novel saliency-aware weighting and edge-aware weighting are introduced for HDR images. They are incorporated into an existing guided image filter to form a perceptually guided image filter. The saliency-aware weighting and the proposed filter are applied to design a new local tone-mapping algorithm for HDR images such that both extreme light and shadow regions can be reproduced on conventional low dynamic range displays. In particular, the proposed filter is applied to decompose the luminance of the input HDR image into a base layer and a detail layer. The saliency-aware weighting is then adopted to design a saliency-aware global tone mapping for the compression of the base layer. The proposed filter preserves sharp edges in the base layer better than the existing guided filter. Halo artifacts are thus significantly reduced in the tone-mapped image. Moreover, the visual quality of the tone-mapped image, especially attention-salient regions, is improved by the saliency-aware weighting. [ABSTRACT FROM PUBLISHER]