Search

This study introduces a novel methodology based on the idea of double Fourier series and coil segmentation, performed based on governing equations, with harmonic magnetic field analysis of a double-sided air-cored superconducting linear synchronous motor for electrodynamic suspension train. This method can solve the harmonic magnetic field generated by arbitrarily shaped coils. First, with rectangular-shaped coils and race-track-shaped coils as examples, the process of calculating harmonic magnetic field using the proposed method is introduced comprehensively, and the influence of the end effect is also considered. Second, based on the solution results of the harmonic magnetic field, a modeling method that can quickly solve no-load superconducting flux linkage, no-load back EMF, and three-dimensional (3-D) electromagnetic forces without losing accuracy is presented, which is verified by finite element simulation. Finally, two static tests are designed. The effectiveness of the proposed method is verified by the test results of static thrust and static normal force. [ABSTRACT FROM AUTHOR]

Constant on-time current mode (COTCM) Buck converters are widely used in power management integrated circuit (ICs) for microprocessors. Small-signal models are necessary tools to design high-quality controllers. Existing models neglect output voltage ripples (OVRs) and spectrum extension caused by switching, which makes significant errors under high control bandwidth. This article adopts Fourier series to describe OVRs precisely. Then, influences of OVRs on COTCM are analyzed. Finally, spectrum coupling from current loop and voltage loop is incorporated to obtain a high-frequency model, and four universal analytical expressions in frequency domain are obtained with the aid of matrix calculation. Based on the proposed model and genetic algorithm, an optimal controller design method is developed. Simulation and experiment validate the accuracy of proposed model and the effectiveness of proposed design method. [ABSTRACT FROM AUTHOR]

An overmodulation method is proposed for an in-wheel system where two motors are coupled to a sum gear. In the dual-motor dual-inverter single shaft systems, the output voltage magnitudes of two inverters are not the same in the overmodulation range due to the angle offset between two motors. In this article, to maintain torque balance in the overmodulation region, holding vectors are defined between adjacent vertices of two voltage hexagons. Around these vectors, the holding region is also defined by the holding angle. If a reference voltage vector is in the holding region, it is modulated to the holding vector; otherwise, it is modulated to the vector on the arc of inscribed circle. For a given the modulation index (MI), the holding angle is obtained based on the Fourier series expansion. The proposed method keeps the output voltages of two inverters the same even if two motors have the angle offset. Further, it has the characteristic of maintaining the linearity between the reference and output MI to the maximum MI. The proposed overmodulation method is demonstrated by simulation and experimental results. [ABSTRACT FROM AUTHOR]

Halbach arrays have been widely implemented in magnetic levitation systems. They concentrate the magnetic field over one side, and their magnetic flux density in the central region can be modeled. This article proposes a novel lookup table-free data-driven method to model the force and torque on a 2-D Halbach array when the magnet array is above a stationary coil. One critical contribution of this article is the rapid and accurate force and torque modeling when the coil is located near the edge of the 2-D magnet array. First, the area under the 2-D Halbach array is divided into a central region, edge regions, and corner regions. Then, nonlinear force and torque components are identified and modeled with a modified third-order Fourier series for force and torque modeling. The proposed model is implemented on an industrial server, and the average computation time is measured to be $2.3 ~\mu \text{s}$. This model is universal for symmetric coils, verified through experimental measurements with circular and square coils of different sizes. The measurement result agrees well with the proposed modeling method, showing that the proposed method is suitable for real-time control of the ironless planar motor. [ABSTRACT FROM AUTHOR]

Fast detection of hazardous objects in millimeter-wave personnel screening can increase the operating efficiency of secure environments. In airports, accurate automatic detection and classification of body-worn objects can reduce the number of pat-downs while keeping the transportation environment safe and secure. Since many benign objects, such as paper and leather, are lossy materials, being able to characterize them and set them aside from the secondary checks will significantly reduce the screening process time. In this article, we introduce an effective image-processing-based method for characterizing lossy materials that might be concealed under clothing at checkpoints. The method has been combined with a modified version of the previously developed algorithm that can be used specifically to characterize lossless materials. The proposed algorithm can automatically distinguish lossless materials from lossy ones and calculate their thickness and permittivities. Starting from the radar reconstructed image showing a cross section of the body, we extract the nominal body contour using the Fourier series, separate body, and object responses, categorize the object as lossy or lossless based on the depression and protrusion of the body contour, and, finally, predict possible values for the object’s permittivity and thickness. Our resulting classification is good, implying fewer nuisance alarms at checkpoints. [ABSTRACT FROM AUTHOR]

This letter presents a Space Vector Pulse Width Modulation (SVPWM) strategy for reducing the DC-link current harmonics in a multi– Voltage Source Inverter (VSI) topology with common DC-link bus. The DC current harmonic reduction is achieved by phase-shifting the PWM pattern of individual VSIs, with the inverters sharing the system total power. Simulation and experimental results are shown to validate the proposal. [ABSTRACT FROM AUTHOR]

The distributed parameters of a non-uniform transmission line (NTL) are assumed to depend on a finite set of unknown parameters, for example, their spatial Fourier series coefficients. The line equations are set up taking random voltage and current line loading into account with the random loading being assumed to be white Gaussian noise in the time and spatial variables. Bypassing over to the spatial Fourier series domain, these line stochastic differential equations (SDEs) are expressed as a truncated sequence of coupled stochastic differential equations for the spatial Fourier series components of the line voltage and current. The coefficients that appear in these stochastic differential equations are the spatial Fourier series coefficients of the distributed line parameters and these coefficients in turn are linear functions of the unknown parameters. By separating these complex stochastic differential equations into their real and imaginary part, the line equations become a finite set of SDEs for the extended state defined to be the real and imaginary components of the line voltage and current as well as the parameters on which the distributed parameters depend. The measurement model is assumed to be white Gaussian noise corrupted versions of the line voltage and current sampled at a discrete set of spatial points on the line and this measurement model can be expressed as a linear transformation of the state variables, i.e, of the spatial Fourier series components of the line voltage and current plus a white measurement noise vector. This work uses sparse matrix factorization using Kronecker product to implement the Fourier unitary transform. This work implements perturbation theory for non-uniform transmission line. The extended Kalman filter (EKF) equations are derived for this state and measurement model and our real timeline voltage and current and distributed parameter estimates show excellent agreement with the true values based on MATLAB simulations. The use of sparse matrix factorization using Kronecker product ease the mathematical complexity and provides compact representation. [ABSTRACT FROM AUTHOR]

This article presents a 3-D semi-analytical model of an axial-flux reluctance coupling. Thanks to the separation of variables method, Fourier series analysis and the convolution theorem (i.e., Cauchy's product), the salient-pole region is modelled by a spatially variable magnetic permeability. Additionally, an iterative algorithm is implemented to account for the magnetic saturation of the iron teeth. The results of the proposed model are compared with a previously published 2-D semi-analytical model, 3-D finite-element method and experimental results. The proposed method appears to be an appropriate tool for the design process of reluctance couplings in cases where the salient poles are saturated. [ABSTRACT FROM AUTHOR]

To realize brushless excitation for an electrical excitation synchronous generator (EESG), a brushless-induced double electrical excitation synchronous generator (IDEESG) with dc excitation is investigated in this study. The static magnetic field is established by injecting dc into the stator excitation windings that are added in the stator slots. Rotor windings are divided into two parts: induction coils and rotor excitation winding. The induction coils cut the static magnetic field and provide dc current for the rotor excitation winding after the rectification. The direction of the currents in the induction coils is constant because of the half-wave rectification. The magnetic flux generated by the currents in the induction coils and rotor excitation winding is added in the air gap to induce the armature coils in the stator. In this study, the structure and the operating principle are examined. The frozen permeability method is adopted to study the influence of the currents in the induction coils and the rotor excitation winding on the magnetic field distribution. The harmonic content of currents in the induction coils is analyzed using the Fourier series form and the effect of the harmonics on the output voltage is also studied. A 1.5 kVA prototype is fabricated to verify the correctness of theoretical analysis and simulation. [ABSTRACT FROM AUTHOR]

A new method extending the scope of the superalgebraically convergent 2-D wave diffraction algorithms is proposed. The principal tool is the construction of an infinitely smooth approximation to the boundary contour. The construction is based on the ideas of Tikhonov’s regularization to the stable summation of the Fourier series and the evaluation of unbounded operators. Both the algorithms for smoothing and the nonsaturated solutions for integral equations together provide the superalgebraic (faster than any algebraic) convergence. The comparison of the algorithms using the original (noninfinitely smooth) parameterization and the infinitely smooth one demonstrates the essential advantage of the latter over the former with respect to accuracy and time consumption. [ABSTRACT FROM AUTHOR]

The stitch wire configuration is widely adopted for large-area IGBT chips. However, an inhomogeneous wire current density introduces uneven self-heating and nonuniform chip heating, which exacerbates the chip thermal stress. In this article, a multicellular electro-thermal model considering the stitch-bonding wires is derived to optimize the wire layout parameters. Furthermore, the current density alleviation of wire bonds is investigated to be the most sensitive and effective method to comprehensively mitigate the thermal nonequilibrium and local overheating. Consequently, an improved multitier layout is proposed to further achieve thermal stress suppression without any additional components and advanced materials. Finally, a triple-tier-bonded IGBT module with optimal design parameters is fabricated to validate the thermal mitigation performance. The prototype experimental results demonstrate that the modeling error is less than 3.0%. The multitier layout decreases the current density by 57.6%, hence, the maximum and average chip temperature are reduced by 21.8% and 12.4%, respectively. [ABSTRACT FROM AUTHOR]

The magnetic field calculation for axial flux motors (AFMs) is always intricate and time-consuming. To this end, a fast quasi-three-dimensional (3D) analytical model is proposed in this paper for magnetic field prediction in AFMs. The 3D magnetic field problem can be simplified into a two-dimensional (2D) one by dividing the AFM into several annular slices in the radial direction. Then, for the first time, the harmonic modeling method (HMM) in Cartesian coordinates is adopted to solve the magnetic field in these slices cut from the AFM. The corresponding electromagnetic parameters of the AFM can be acquired subsequently. The critical step for the field prediction of using HMM in Cartesian coordinates is to adopt a variable substitution method when solving the partial differential equations. Next, the magnetic saturation of soft-magnetic material within AFMs is considered by adopting an iterative approach. Ultimately, the effectiveness of the proposed quasi-3D analytical model is validated by the nonlinear finite element analysis (FEA). The proposed analytical model is computationally efficient, which makes it suitable for the preliminary design of AFMs. [ABSTRACT FROM AUTHOR]

Oscillations of grid-connected voltage source converter (VSC) usually reaches sustained state because of the limiters in controller. Describing function has been adopted to analyze the amplitude and frequency of the sustained oscillations, but high-order oscillation components caused by the limiter are ignored in previous literatures. This letter proposes an analysis method for sustained oscillations which considers high-order oscillation components. This method could obtain a more precise oscillation frequency and the amplitude of 1st, 2nd, and 3rd order components. The proposed method is verified by case studies and simulations in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

This article presents a generalization of an analytical model of an axial-flux permanent-magnet machine to any magnet shape. It uses an existing model, which computes the 3-D magnetic-flux density by the separation of variables and a finite-difference method. The original magnet shape is modified by adding a radial dependency to the Fourier series description of permanent magnets (PM) magnetization. The model is then developed for a general complex magnet shape. As an example, the model will be computed for a circular magnet shape and will be compared with finite-element analysis. [ABSTRACT FROM AUTHOR]

This article considers the Nussbaum gain adaptive control issue for a type of nonlinear systems, in which some sophisticated and challenging problems, such as periodic disturbances, dead zone output, and unknown control direction are addressed. The Fourier series expansion and radial basis function neural network are incorporated into a function approximator to model time-varying-disturbed function with a known period in nonlinear systems. To deal with the problems of the dead zone output and unknown control direction, the Nussbaum-type function is recommended in the design of the control algorithm. Applying the Lyapunov stability theory and backstepping technique, the proposed control strategy ensures that the tracking error is pulled back to a small neighborhood of origin and all closed-loop signals are bounded. Finally, simulation results are presented to show the availability and validity of the analysis approach. [ABSTRACT FROM AUTHOR]

In this article, we propose steady-state modeling of dc–dc converters driven by multiple pulsewidth modulation (PWM) signals. The proposed dc–dc converter modeling uses a switched state-space framework, and the switching signal discontinuities are represented by a Fourier series to obtain the average model. The advantage of the proposed modeling is that it is not dependent on the dc–dc converter topology, and the dimension of the state-space model does not increase with the number of storage devices. Additionally, the duty cycle and phase displacements among the driving PWM signals can be arbitrary and systematically modeled. The effectiveness of the proposed modeling is supported by simulation and experimental results. [ABSTRACT FROM AUTHOR]

In robotics, ergodic control extends the tracking principle by specifying a probability distribution over an area to cover instead of a trajectory to track. The original problem is formulated as a spectral multiscale coverage problem, typically requiring the spatial distribution to be decomposed as Fourier series. This approach does not scale well to control problems requiring exploration in search space of more than two dimensions. To address this issue, we propose the use of tensor trains, a recent low-rank tensor decomposition technique from the field of multilinear algebra. The proposed solution is efficient, both computationally and storagewise, hence making it suitable for its online implementation in robotic systems. The approach is applied to a peg-in-hole insertion task requiring full 6-D end-effector poses, implemented with a seven-axis Franka Emika Panda robot. In this experiment, ergodic exploration allows the task to be achieved without requiring the use of force/torque sensors. [ABSTRACT FROM AUTHOR]

Motor drive systems with long feeder cables are widely used in mining and energy sectors, such as offshore oil and gas drilling. In recent decades, to prevent issues with electromagnetic interference, power quality standards have been defined for the 2–150 kHz frequency range. In order to comply with these standards, manufacturers need to design filters to avoid exceeding the thresholds set by the standards. An important aspect that needs to be considered is the accurate modeling of currents circulating through common-mode loops. This article addresses this modeling by using a mathematical approach. The power cable’s common-mode model is extracted from the measurement data using the finite-element method via finding the effective permittivity of the PVC materials. The common-mode noise sources, including the grid side voltage through the front-end diode rectifier and the output voltage through the rear-end inverter, are both modeled by extracting the Fourier series calculations. Consequently, noise emissions circulating through different common-mode loops are analytically modeled. Through the proposed modeling strategy, the harmonic spectrum of resonances can be precisely analyzed. The results are validated through simulation and experimental data. [ABSTRACT FROM AUTHOR]

This article develops a new closed-form analytical solution to the harmonic spectrum of the full-bridge (FB) modular multilevel converter (MMC) with phase shifted carrier pulse width modulation. It considers FB-MMC operation in boost mode where the negative-voltage states of the FB submodules (SMs) are utilized to extend the ac operating voltage range and/or reduce the dc link voltage which is known to reduce the energy storage requirement. The solution is based on double Fourier series expansion in two variables. The harmonic distribution of the output voltage is analyzed and the effects of the modulation index and the number of SMs on the output voltage harmonics are revealed. The influence of the upper/lower arm carrier phase shift angle is also investigated. Using the analysis, selection of the number of SMs, the modulation index and the upper/lower arm carrier phase shift angle are specified for output voltage harmonic minimization. The findings are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This work continues the development of the ray-tracing method of de Jong (2021) for computing the scattered fields from metasurfaces characterized by locally periodic reflection and transmission coefficients. In this work, instead of describing the metasurface in terms of scattering coefficients that depend on the incidence direction, its scattering behavior is characterized by the surface susceptibility tensors that appear in the generalized sheet transition conditions (GSTCs). As the latter quantities are constitutive parameters, they do not depend on the incident field and, thus, enable a more compact and physically motivated description of the surface. The locally periodic susceptibility profile is expanded into a Fourier series subject to a spatially varying phase parameter, and the GSTCs are rewritten in a form that enables them to be numerically solved for the reflected and transmitted surface fields. The phase parameter can either be determined from a prescribed surface transformation or extracted from known surface susceptibilities. A method for the extraction of this phase parameter from a susceptibility profile using a spatial variant of the short-time Fourier transform (STFT) is proposed. The scattered field at arbitrary detector locations is constructed by evaluating critical-point contributions of the first and second kinds using a forward ray-tracing (FRT) scheme. The accuracy of the resulting framework has been verified with an integral equation-based boundary element method (BEM)-GSTC full-wave solver for a variety of examples, such as a periodically modulated metasurface, a metasurface diffuser, and a beam collimator. [ABSTRACT FROM AUTHOR]

This article deals with 2-D modeling of coupled vibrations of finite piezoelectric resonators. A general solution for all the physical quantities in the Cartesian and cylindrical coordinate systems is deduced from the governing equations by expansion in series summation of trigonometric functions of thickness coordinate and trigonometric or Bessel functions of the lateral one. The essential difference between this model and the earlier ones is that instead of expressing mainly in the thickness coordinate and integration through the thickness, the solutions are expressed in the form of double Fourier series augmented by single Fourier or Fourier–Bessel series, which contributes to better satisfy the mechanical and electrical boundary conditions. The dynamic stiffness matrix of the system is developed. Electrical impedances of a typical piezoelectric parallelepiped under stress-free and symmetrical loading conditions and its frequency spectrum for different width-to-thickness ratios are calculated using our model as well as by the finite element method. A comparison shows an excellent agreement. Finally, theoretical and measured electrical impedances of a piezoelectric parallelepiped and a piezoelectric disk are compared and discussed. The 2-D theoretical model proposed here is shown to be accurate and efficient for coupled vibration analysis of piezoelectric resonators and is applicable for any set of finite dimensions and crystal symmetry. [ABSTRACT FROM AUTHOR]

This article presents a high-fidelity analytical solution and a fast integrated optimization method for vernier machines. First, a harmonic modeling method (HMM) is adopted to obtain the magnetic field distribution of vernier machines. Particularly, the stator teeth of vernier machines are divided into several blocks to take account of the local magnetic saturation of soft-magnetic material. Then, the electromagnetic parameters, such as the average torque, torque ripple, and efficiency, can be calculated via the analytical model. Next, the proposed harmonic model is combined with the nondominated sorting genetic algorithm II (NSGA-II) to determine a multiobjective optimal design for the studied vernier machine. This integrated optimization method can save computation time, because the data interaction process between the finite-element analysis (FEA) software and the optimization software is eliminated. Finally, the performances of the optimal case are verified by both FEA and experiments with the prototype. [ABSTRACT FROM AUTHOR]

Fault detection of a rotating rectifier for a wound-rotor synchronous starter/generator (WRSSG) without a rotor position sensor in the stationary state is necessary for a successful engine start. Based on high-frequency (HF) voltage injection, a novel fault detection method of the rotating rectifier for the WRSSG in the stationary state is proposed. The rotating HF voltage is imposed on the stator windings of the main machine, and the HF feature current signal extracted on the stator windings of the main exciter is used for fault detection. In this article, the HF current signal in the main exciter with the rotating rectifier under different working conditions is analyzed first. To obtain the HF response current on the stator windings of the main exciter, the HF model of the WRSSG is analyzed. Through the Fourier series, the HF feature current signal together with fault detection is achieved. Compared with the existing fault detection methods, the proposed method shows no dependency on the rotor position information. Experimental results verify the feasibility and effectiveness of this method. [ABSTRACT FROM AUTHOR]

This article presents an improved analytical spatial harmonics subdomain (SHSD) model for analyzing the influence of individual spatial harmonics, in stator magneto-motive forces (MMFs), on the performance of multiphase cage rotor induction motors (CRIMs). The proposed SHSD model is an extension of conventional techniques that consider each MMF spatial harmonic, caused by stator slots with tooth-tips, to be individual excitations when quantitatively analyzing the resulting physical effects. The solution domain was divided into four subdomains (SDs) in 2-D polar coordinates, including 1) rotor bars described by the Helmholtz equation; 2) air gaps; 3) slot openings described by Laplace’s equation; 4) stator slots represented by pure forced vibration equations. Current density in the stator structure was decomposed in a Fourier series of position angles to obtain MMF spatial harmonics. This produced a set of pure forced vibration equations in the stator slots, which were first solved in 2-D polar coordinates rather than the typical Poisson’s equation. This approach establishes a relationship between electromagnetic performance and stator parameters, for further optimization of IMs and analysis of electromagnetic vibrations. The proposed analytical model was validated using a series of finite element simulations, which exhibited high accuracy and computational efficiency. [ABSTRACT FROM AUTHOR]

An aircraft transition connects two flight conditions and is a fundamental component of aerospace operations. For achieving a seamless transition that accurately connects two steady flights, a hierarchical parameterization method is developed in this article for generating smooth flight trajectories satisfying hard boundary constraints on controls and control derivatives of all orders. The proposed work is based on a trigonometric series parameterization of control variables and hierarchically parameterizes the series coefficients with flat and logistic functions, leading to a new set of coefficients and a formulation that inherently guarantees the desired conditions. The new set of coefficients can be determined by optimization methods and can be integrated in existing methods with the advantage of streamlining the problem formulation. Simulation studies including comparisons demonstrate the effectiveness and performance of the proposed method. [ABSTRACT FROM AUTHOR]

Objective: To investigate the importance of membrane charge oscillations and redistribution in multi-compartmental ultrasonic neuromodulation (UNMOD) intramembrane cavitation models. Methods: The Neuronal Intramembrane Cavitation Excitation (NICE) model and multiScale Optimized model of Neuronal Intramembrane Cavitation (SONIC) of UNMOD are compared for a nanoscale multi-compartmental and point neuron approximation of the bilayer sonophore and surrounding proteins. The temporal dynamics of charge oscillations and their effect on the resulting voltage oscillations are investigated by fourier series analysis. Results: Comparison of excitation thresholds and neuronal response between nanoscale multi-compartmental and point models, implemented in the SONIC and NICE framework, demonstrates that the explicit modeling of fast spatial charge redistribution is critical for an accurate multi-compartmental UNMOD-model. Furthermore, the importance of modeling partial protein coverage is quantified by the excitability thresholds. Subsequently, we establish by fourier analysis that these charge oscillations are slowly changing in time. Conclusion: Fast charge redistribution significantly alters neuronal excitability in a multi-compartmental nanoscale UNMOD-model. Also the mutual exclusivity between protein and sonophore coverage should be taken into account, when simulating the dependency of neuronal excitability on coverage fractions. Charge oscillations are periodic and their fourier components change on a slow timescale. Furthermore, the resulting voltage oscillations decrease in energy with overtone number, implying that an extension of the existing multiscale model (SONIC) to multi-compartmental neurons is possible by taking into account a limited number of fourier components. Significance: First steps are taken towards a morphologically realistic and computationally efficient UNMOD-model, improving our understanding of the underlying ultrasonic neuromodulation mechanisms. [ABSTRACT FROM AUTHOR]

This paper combines the use of multi-phase configurations and current harmonic injection methods to achieve significantly improved performance for doubly salient synchronous reluctance machines (DS-SRMs). In order to understand the torque production mechanism of multi-phase DS-SRMs with current harmonic injection, some general analytical torque models have been developed. The models are based on Fourier Series analysis of self- and mutual-inductances. It has been established that with current harmonic injection, the torque ripple of both 5-phase and 6-phase DS-SRMs can be significantly reduced and the average torque can be enhanced. It contrast, harmonic injection always has a detrimental impact on 4-phase machines. The investigations of losses and dynamic performance with current harmonic injection for multi-phase machine have also been carried out and demonstrated that the proposed method can improve the efficiency in constant torque region and maintain comparable performance to fundamental current supply in the flux weakening region. Experimental validation based on single layer, 6-phase, DS-SRM has been performed. [ABSTRACT FROM AUTHOR]

The electrodynamic suspension reaction sphere (EDSRS) is regarded as a novel actuator for the spacecraft attitude control system. The omnidirectional rotation of the EDSRS spherical rotor brings about the dynamic distortion of the electromagnetic force and torque characteristics. With the mechanical structure of the EDSRS simplified and equivalent to multi-degrees of freedom (DOF) single-sided linear induction motor (LIM), this article first proposes a 3-D LIM analytical electromagnetic force model by employing the electromagnetic physical quantities in the 2-D Fourier series expansion form. Then, an analytical electromagnetic force and torque model considering the electromagnetic dynamic distortion effect (EDDE) of the EDSRS is established based on the previous LIM force model according to the motion decomposition principle. Finally, the proposed analytical EDDE model is experimentally validated on the developed laboratory prototype. [ABSTRACT FROM AUTHOR]

This article is concerned with the identification of industrial robot dynamics parameters, and an identification method based on a nonlinear friction model and a least squares (LS) with symbiotic organisms search (SOS) algorithm is proposed. First, according to the friction characteristics of robot joints, for the nonlinear Tustin friction model, two parameters are introduced to describe the Stribeck characteristics of Coulomb friction and static friction. Then, the joint velocity trajectory that can offset the nonfriction torque during the forward and reverse rotation is designed, and friction parameters are estimated by using LS. Based on the optimal criterion constructed by Hadamard’s inequality, the excitation trajectory represented by the Fourier series is designed, and the combined inertial parameter set is estimated by using LS. Second, select the minimum inertial parameters and friction parameters (minimum dynamic parameters) as the center points to search the upper and lower bounds; design the fitness function with adjustable weights of each joint and use the SOS algorithm to estimate the minimum dynamic parameter set as a whole. Finally, a variety of parameter identification algorithms are applied to the Stäubli TX-90 robot under the same excitation trajectory. The experiment results show that the root-mean-square (rms) error of the joint torque estimated by the proposed method is the smallest. By executing the verification trajectory, the experiment results show that the rms error of the joint torque is small and the correlation coefficient is close to 1, thereby verifying the effectiveness of the estimated model for different motion trajectories. [ABSTRACT FROM AUTHOR]

The Fourier-series-based insulated-gate bipolar transistor (IGBT) model has been very effective in simulating its switching behaviors and meanwhile, reflecting carrier dynamics. However, in turn-on process, such a model has difficulty in distinguishing the boundary between undepleted area and depletion layer of the drift region due to Gibbs phenomenon and therefore, cannot accurately describe the carrier behavior of carrier storage region (CSR). In this study, the Fourier-series-based model is modified to determine the more precise depletion layer edge for turn on. This is achieved by utilizing the actual characteristics of the carrier concentration gradient at the edge of CSR in turn-on process. Such a modified model is implemented in MATLAB/Simulink and it can better reflect the depletion layer and simulate the distribution of both the carrier concentration and electric field during turn-on process. It corrects the unreasonable voltage tail caused by the error of drift region voltage calculation in previous models. The results of the proposed model under both the resistive load and inductive load are in good agreement with TCAD. Such a modified model can more accurately simulate both carrier dynamics and switching behaviors in the turn-on process. [ABSTRACT FROM AUTHOR]

This paper proposes an analytic model of a resonant MEMS mirror with electrostatic actuation based on a Fourier series approximation for both the comb drive torque and the input waveform and verifies the model by measurements using rectangular input waveforms with various duty cycles. The analytic model is derived by the perturbation method, results in slow flow evolution in amplitude and phase with dynamic influence matrices and vectors and also provides the local dynamics for each equilibrium described by a Jacobian matrix. An analysis of the dynamic influence matrices and vectors provides understanding of the mirror dynamics by frequency components of the input waveform and the comb drive capacitance. The asymptotic behavior at zero amplitude provides the transition curve in an extended dynamic model, which corresponds to the well-known Mathieu’s equation solely with the constant and fundamental frequency components of the input waveform. The measurement results verify the proposed model, showing less than ±0.06 % frequency error for large amplitudes and ±0.47 % for small amplitudes, which corresponds to ±1.2 Hz and ±9.6 Hz for the case of a mirror with 2 kHz natural frequency, respectively. Measurements of local dynamics and transition curves also show a good agreement with the proposed model, which can be used for a fast and accurate analysis of resonant MEMS mirrors for high precision applications. [2020-0387] [ABSTRACT FROM AUTHOR]

Since the permeability of ferromagnetic materials is sensitive to the stress changes, it is feasible to acquire the stress level through detecting the change in permeability. In this study, to explore the distribution of stress or residual stress along the depth direction, a multi-layer model was established and a new inversion algorithm was proposed; and the hypothesis of uniformity of the material’s physical properties for each layer was introduced. Under laboratory conditions, the four-point bending experiment was then implemented with a sample of 45# steel. Global Fourier series fitting based on the least-squares method was used for signal process. The amplitude ratio of the induced voltage to the excitation current was extracted. The effective permeability and the associated hysteresis angle at the 0.25 mm deflection were calculated and presented good regular variations. Finally, under the 0.25 mm deflection, the effective permeability change along the depth was obtained, and the inversely fitted curve was consistent with the theoretical curve. It is verified that the sensor has good robustness by adding deviation of the detection depth. Thereby, it is feasible to test stress or residual stress as a function of depth by multi-frequency eddy current (EC) method. [ABSTRACT FROM AUTHOR]

This article presents an adaptive waveform design method using multitone sinusoidal frequency modulation (MTSFM). The MTSFM waveform's modulation function is represented as a finite Fourier series expansion. The Fourier coefficients are utilized as a discrete set of design parameters. These design parameters can be modified to shape the spectrum, auto-correlation function (ACF), and ambiguity function (AF) shapes of the waveform. The MTSFM waveform model naturally possesses the constant envelope and spectral compactness properties that make it well suited for transmission on practical radar/sonar transmitters which utilize high power amplifiers. The MTSFM has an exact mathematical definition for its time-series using generalized Bessel functions which allow for deriving closed-form analytical expressions for its spectrum, AF, and ACF. These expressions allow for establishing well-defined optimization problems that finely tune the MTSFM's properties. This adaptive waveform design model is demonstrated by optimizing MTSFM waveforms that initially possess a “thumbtack-like” AF shape. The resulting optimized designs possess substantially improved sidelobe levels over specified regions in the range-Doppler plane without increasing their time-bandwidth product. Simulations additionally demonstrate that the optimized thumbtacklike MTSFM waveforms are competitive with thumbtacklike phase-coded waveforms derived from design algorithms available in the published literature. [ABSTRACT FROM AUTHOR]

In this article, accurate modeling and decoupling control of a linear ironless PM actuator are implemented for precision engineering. Given the fringing effect due to the finite length, the magnetic field of the PMs and the three-phase winding are both calculated by applying an improved Fourier series expansion. Subsequently, based on a distributed model, the associated flux linkage and winding inductances are obtained and validated. Compared with rotary motors of physical symmetry, the winding inductance matrix makes the electrical model of the finite-long linear actuator present a new non-uniform form, to which the classic decoupling technique is inapplicable directly. Therefore, improved decoupling strategies are established utilizing the zeroth-order approximation of the inductances based on the $dq0$ transformation, as well as a real-time updating scheme. Physical experiments show that high-order harmonics are eliminated by applying the non-uniform model, which makes it effective and applicable. [ABSTRACT FROM AUTHOR]

A novel periodic phase modulation method is proposed and verified for the fast diagnosis of phased array. Taking the diagnosis of receiving paths as an example, its principle is as follows. Periodic phase modulations with different frequencies are added to each phase shifter of the phased array. Because of the periodic modulation, harmonic components are generated in all the elements. As modulation frequencies added to all the elements are different from each other, the generated harmonic components have different frequencies correspondingly. If some elements suffer failure, the corresponding harmonic components will vanish from the output of the power combiner. Therefore, the faulty elements can be located by analyzing the spectrum of the received signal after the power combiner. The proposed method needs no the auxiliary hardware and its signal processing is concise. An eight-element $S$ -band phased array is fabricated to examine its effectiveness. [ABSTRACT FROM AUTHOR]

This article proposes an improved analytical approach to the electromagnetic performance of a linear oscillatory actuator, considering the end and stacking effects of the outer and inner cores. A simplified analytical model is defined with several assumptions taking into account the end effect of the outer and inner core in the $z$ -axis direction. Maxwell’s equations, partial differential equations, and Fourier series are used to derive the general solution in each subdomain of the proposed model. By calculating the boundary conditions applied in the $r$ - and $z$ -directions, unknown coefficients of analytical solutions are derived. The electromagnetic performances are expressed mathematically from the derived analytical solutions. To increase the accuracy of the proposed analytical method, a stacking factor that considers manufacturability is applied to the calculation of the electromagnetic performances. The validity of the proposed analytical method is verified by comparing the results of 2-D and 3-D finite-element analyses and the experiment. [ABSTRACT FROM AUTHOR]

The lumped-parameter thermal network (LPTN) has been widely used in the thermal analysis for electrical machines. Nevertheless, since the thermal resistances are defined based on the one-dimensional (1-D) heat transfer equation, it will cause the misestimation of the average temperatures when the thermal model extends to two dimensions or three dimensions. In this article, a hybrid thermal model utilizing the synergies of LPTN and 2-D analytical thermal models is developed to address this issue and to predict accurate critical temperatures, especially the average and maximum temperatures of the active and end windings. The 2-D analytical thermal models are obtained by solving the Poisson's equations with the Dirichlet boundary conditions extracted from the LPTN. The derived analytical solutions are expressed as the Fourier series, which can be further simplified by utilizing the first term only to represent average and maximum temperatures with sufficient accuracy and short computation time. The hybrid thermal model is applied to a totally enclosed forced convection permanent magnet synchronous machine and validated by numerical techniques and experiments. [ABSTRACT FROM AUTHOR]

Finite rate of innovation (FRI) is a powerful reconstruction framework enabling the recovery of sparse Dirac streams from uniform low-pass filtered samples. An extension of this framework, called generalised FRI (genFRI), has been recently proposed for handling cases with arbitrary linear measurement models. In this context, signal reconstruction amounts to solving a joint constrained optimisation problem, yielding estimates of both the Fourier series coefficients of the Dirac stream and its so-called annihilating filter, involved in the regularisation term. This optimisation problem is however highly non convex and non linear in the data. Moreover, the proposed numerical solver is computationally intensive and without convergence guarantee. In this work, we propose an implicit formulation of the genFRI problem. To this end, we leverage a novel regularisation term which does not depend explicitly on the unknown annihilating filter yet enforces sufficient structure in the solution for stable recovery. The resulting optimisation problem is still non convex, but simpler since linear in the data and with less unknowns. We solve it by means of a provably convergent proximal gradient descent (PGD) method. Since the proximal step does not admit a simple closed-form expression, we propose an inexact PGD method, coined Cadzow plug-and-play gradient descent (CPGD). The latter approximates the proximal steps by means of Cadzow denoising, a well-known denoising algorithm in FRI. We provide local fixed-point convergence guarantees for CPGD. Through extensive numerical simulations, we demonstrate the superiority of CPGD against the state-of-the-art in the case of non uniform time samples. [ABSTRACT FROM AUTHOR]

An accurate analytic model of a parametrically driven resonant MEMS mirror is proposed using a Fourier series based approximation for out-of-plane comb drive torque. The analytic model consists of slow evolution equations of the amplitude and phase derived by the averaging theorem of perturbation theory. Based on the model, analytic expressions of the primary frequencies and Jacobian are derived, which are computationally efficient and provide additional information on the steady state solutions and local dynamics. Measurement results of frequency response show less than ±0.04 % in frequency errors from the model for various input voltages, i.e. less than ±0.8 Hz for the case of a mirror with 2 kHz natural frequency. The eigenfrequency and damping of the Jacobian matrix show a good agreement with measured local dynamics as well. This verifies the high accuracy of the proposed model, which can be used for improvement of the MEMS mirror design parameters and control design for large amplitude operation. [2020-0158] [ABSTRACT FROM AUTHOR]

The noninvasive method for monitoring urine collection in the bladder is highly recommended for paraplegia patients. These patients are unable to discharge urine at the right time due to a weaker sensation for bladder volume. If the urine is not discharged in time, then the bladder size will increase and affect the neighboring organs and tissues. Electrical impedance tomography (EIT) is a noninvasive alternative method that can be used for bladder status monitoring. Size estimation of the bladder with EIT can clarify the bladder status. The bladder is a nonuniform structure with complex shape; therefore, higher order Fourier series is needed to represent the true shape. In estimating the higher order Fourier coefficients, the performance of a conventional modified Newton–Raphson (mNR) algorithm does not give the desired performance. In this article, the gravitational search algorithm (GSA) that is known for solving optimization problems in high-dimensional search space is proposed for the shape estimation of the bladder. GSA is a global optimization algorithm that has fast convergence and does not require the computation of Jacobian. Numerical experiments and phantom studies are performed to estimate the bladder size, and the results showed good performance. [ABSTRACT FROM AUTHOR]

A study on the transient behavior of a single-loop optoelectronic oscillator (OEO) under a single sinusoidal radio frequency (RF) signal injection is presented. Considering only the phase perturbation imposed by the external RF signal, the phase-dynamic equation is solved to analyze the frequency settling behavior of the loop. A closed form expression for the required time of an OEO under RF injection-locking, reaching the steady state condition, is derived in terms of the initial phase difference, beat frequency and injection signal strength. The phase modulated signal, which is responsible for the perturbation of the free running oscillation, is expanded in a Fourier series and the expression for the output RF spectrum of the injection pulled OEO is derived. The injection-pulling dynamics approach is used to describe the phase noise of the OEO and also, the influence of the phase settling time constant on the phase noise of the injection-locked OEO is studied. The experimental results corroborating the theoretical findings are given. [ABSTRACT FROM AUTHOR]

A transient model of a rectangular N-layer structure with an arbitrary number of rectangular heat sources on the top surface is obtained by Fourier series solution. As power modules can be closely approximated by this type of structure, the model may be used to accurately estimate the temperature field occurring in such modules. The Fourier-based method developed in this work is compared with a finite-element model and an excellent matching (under 2% error) in the transient region is found. An experimental validation is performed using a half-bridge silicon carbide power module monitored by a high frame-rate thermal camera. After the model outputs have been compensated to match the limited frequency response of the camera, a good matching is found between model and experiment (under 6% error). [ABSTRACT FROM AUTHOR]

Voronoi diagrams specify the coverage regions of base stations in cellular radio systems. Classical Voronoi diagrams are made up of regions which are convex polygons, but this is the case only for an unrealistic single-slope pathloss model. We provide a new algorithm which computes arbitrarily accurate boundaries of coverage regions under a very general pathloss model, which requires only that the radio signals decrease monotonically with distance and asymptotically as some power of the distance. The new algorithm is applicable to general cellular environments with multi-slope pathloss conditions, including those in vehicular-to-everything (V2X) communications. [ABSTRACT FROM AUTHOR]

Power quality in electrical systems is a basic requirement that should be guaranteed. Nonetheless, the increase of power-electronics-based applications and other nonlinear loads have induced harmonic distortion degrading the power quality; therefore, effective methods to measure and suppress such distortion need to be developed. The main contributions of this article are the following: the development of a novel fast-converging optimal estimator to determine online the harmonic components of a time-varying signal, which can be used for analysis and control purposes; the usage of the estimator to generate reference signals for an optimal control system in order to suppress the harmonics components; and the experimental validation of the proposed methodology as a feasible solution for industrial applications. The proposal considers practical assumptions such as the signal to be analyzed is corrupted with noise and contains time-varying harmonics (i.e., no steady-state condition is assumed). As an application of the harmonic estimator, the following two experimental tests are carried out: first, the optimal determination of the harmonic components of the current waveform in a nonlinear load, and second, the usage of harmonics information to mitigate them through of an active power filter, which is controlled by using an optimal trajectory tracking control scheme. [ABSTRACT FROM AUTHOR]

This article develops a new closed-form analytical solution to the harmonic spectrum of the pulsewidth modulated (PWM) output voltage of the single-phase inverter connected to the dc bus with considerable voltage ripple. The solution is based on a double Fourier series expansion in two variables. As the single-phase inverter forms the basic building block of most converters, the developed expressions can be applied to various topologies. This article first identifies the interactions of a single-frequency sinusoidal modulation signal and the carrier signal with the dc bus voltage harmonics. The dc bus voltage harmonics are constrained in this article to multiples of the inverter output voltage fundamental frequency. The analysis is then extended to include a multifrequency modulation signal. Starting from the general solution, new expressions for the output voltage harmonics of the modular multilevel converter (MMC) are developed. The low-capacitance MMC is chosen in this analysis due to inherent low-frequency voltage oscillations in the converter internal capacitors. The MMC analytical harmonic spectrum can incorporate the effects of the circulating current control and third harmonic injection PWM, by including the second- and third-order harmonic components in the modulation signal, respectively. The MMC analytical harmonic spectrum is benchmarked against the experimental results. [ABSTRACT FROM AUTHOR]

The static excitation part of a brushless wound rotor hybrid excitation generator without an exciter (brushless WRHEG) is analyzed in this paper. The DC stator excitation windings and rotor harmonic coils are placed in the iron core as the excitation part, so that the brushless excitation for a wound rotor hybrid excitation generator (WRHEG) can be realized. In this study, the selection of stator excitation windings and rotor harmonic coils, which are essential for achieving of the brushless excitation, is providing. The effect of the static magnetic field on the air-gap magnetic field is studied theoretically. The harmonic content of the air-gap magnetic field is analyzed by Fourier series form and the effect of harmonics on the output voltage is also investigated. The influence of the static excitation field on the iron loss is also considered. A 1.5 kVA prototype is fabricated to verify the validity of the theoretical and Finite Element (FE) analysis. The output voltage under the no-load and the rated load conditions are measured. The field regulation capacity and the efficiency of the brushless WRHEG are tested. It shows that the brushless excitation is achieved by remaining the operating performance of WRHEG unchanged. [ABSTRACT FROM AUTHOR]

The circuit averaging technique has long been used as the basis for modeling the behavioral effects of switched-mode pulsewidth-modulated (PWM) dc–dc power converter circuits due to its simplicity and efficiency in simulation. However, circuit-averaged models struggle to capture the effects of higher order harmonics on the output waveforms. Alternatively, multiharmonic models that capture high-frequency characteristics of output waveforms are typically very complex and computationally expensive. A general, efficient, and accurate multiharmonic modeling and simulation technique for low-power on-chip PWM dc–dc converters is presented in this article. The technique is based on the large-signal averaged model of the PWM switch cell and on the Fourier series expansion of the typical converter waveforms. Its applicability range includes current-mode-controlled dc–dc converters. The method is exemplified on a buck and on a boost converter and achieves a speedup of one order of magnitude with an accuracy loss below 3% over the transistor-level simulation. The method accounts for nonideal circuitry and supports any number of harmonics. [ABSTRACT FROM AUTHOR]

This article presents techniques into prediction and control of the radiated harmonic levels in time-modulated antenna arrays (TMAs). The effect of ramping on the controlling switching waveform, due to slew in the RF switches, is analyzed first. This is followed by a novel technique for controlling and reducing the fundamental carrier component (due to the Fourier series 0 Hz term) that is always produced by TMAs. A new bespoke, steerable, TMA RF hardware test platform is presented, using three gain states to pragmatically implement the proposed carrier reduction technique. The platform implementation utilizes binary logic control interfaces to the TMA, rather than analog control interfaces. Laboratory measurements using the test platform demonstrate a 16.5 dB reduction (limited by PCB emissions) in the level of the fundamental carrier component relative to the steered first harmonic, from a possible reduction of 21.3 dB. The array gain for the first harmonic beam is 2 dBi. [ABSTRACT FROM AUTHOR]

Multiple pulsed loads arise in all-electric ship power systems, which consume an enormous amount of energy in a short time. Moreover, pulsed load requirements may change rapidly, and a fast regulation method is indispensable for optimal energy management. To this end, the article formulates an optimal coordination problem and develops an online algorithm for a shipboard power system, where the periodic operation of pulsed loads is utilized. The problem is divided into two parts: i) the energy allocation for each pulsed load is optimized to maximize total utility; ii) the joint charging period is determined to supply pulsed loads in a shorter cycle. In the solution method, the Fourier series is used to represent the operation period of pulsed loads and accelerate the algorithm. Case studies on a shipboard power system with eight pulsed loads show that the proposed algorithm is effective, and applicable for online use. [ABSTRACT FROM AUTHOR]

Multipactor, a sustained electron avalanche driven by radiofrequency (RF), has been extensively studied due to its importance in all RF vacuum electronic devices. In particular, much effort has been made in understanding the phenomenon to mitigate it in real systems. On the other hand, some have used what is often seen as a disastrous effect for benefit. In this article, we study a novel way of using multipactor discharges for harmonic generation. We take advantage of the intrinsic phase-focusing mechanism of multipactor as a natural charge-bunching mechanism. The theory along with some validating test cases will be presented. Potential (beneficial) applications and ramifications of this phenomenon will be briefly discussed. [ABSTRACT FROM AUTHOR]