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Presented in this paper is a direct model predictive control (MPC) for directly controlling the rotor speed and flux of an inverter-fed induction motor, which is also applicable to induction generators. Discrete dynamic model of the induction machine is applied in stationary reference frame with pre-set present and past reference values of the speed and rotor flux for generating the stator current references The uniqueness of the MPC proposed herein is that it does not require outer cascade proportional plus integral (PI) controllers used for regulating rotor speed and flux. Elimination of the outer loop cascade is made possible in this article by the introduction of a unique four-term cost function comprising of weighted magnitudes of the errors between four measured state variables and their reference commands. The four state variables in the unique cost function are the rotor speed, the rotor flux linkage, quadrature axis and direct axis stator currents. The MPC minimizes the cost function at every switching instance by selecting the switching states that gives the least cost function. Consequently, the selected optimal switching states are used to switch optimal inverter output voltages across the machine's stator terminals. As a precursor for obtaining an optimal rotor flux command in the MPC for every torque output, another unique efficiency improvement scheme is developed, which uniquely determines the stator angular velocity and the rotor flux that minimizes the core and copper losses while maintaining a constant slip operation. Therefore, efficacy of the proposed direct model predictive control scheme is verified by comparing its results to results obtained from equivalent vector control on equivalent machine. Results presented show lower loss regime with MPC on optimal stator angular velocity and rotor flux than vector control. [ABSTRACT FROM AUTHOR]

This article presents an in-depth analysis of three advanced strategies to tune fractional PID (FOPID) controllers for a nonlinear system of interconnected tanks, simulated using MATLAB. The study focuses on evaluating the performance characteristics of system responses controlled by FOPID controllers tuned through three heuristic algorithms: Ant Colony Optimization (ACO), Grey Wolf Optimizer (GWO), and Flower Pollination Algorithm (FPA). Each algorithm aims to minimize its respective cost function using various performance metrics. The nonlinear model was linearized around an equilibrium point using Taylor Series expansion and Laplace transforms to facilitate control. The FPA algorithm performed better with the lowest Integral Square Error (ISE) criterion value ( 297.83 ) and faster convergence in constant values and fractional orders. This comprehensive evaluation underscores the importance of selecting the appropriate tuning strategy and performance index, demonstrating that the FPA provides the most efficient and robust tuning for FOPID controllers in nonlinear systems. The results highlight the efficacy of meta-heuristic algorithms in optimizing complex control systems, providing valuable insights for future research and practical applications, thereby contributing to the advancement of control systems engineering. [ABSTRACT FROM AUTHOR]

This article presents an in-depth analysis of three advanced strategies to tune fractional PID (FOPID) controllers for a nonlinear system of interconnected tanks, simulated using MATLAB. The study focuses on evaluating the performance characteristics of system responses controlled by FOPID controllers tuned through three heuristic algorithms: Ant Colony Optimization (ACO), Grey Wolf Optimizer (GWO), and Flower Pollination Algorithm (FPA). Each algorithm aims to minimize its respective cost function using various performance metrics. The nonlinear model was linearized around an equilibrium point using Taylor Series expansion and Laplace transforms to facilitate control. The FPA algorithm performed better with the lowest Integral Square Error (ISE) criterion value (297.83) and faster convergence in constant values and fractional orders. This comprehensive evaluation underscores the importance of selecting the appropriate tuning strategy and performance index, demonstrating that the FPA provides the most efficient and robust tuning for FOPID controllers in nonlinear systems. The results highlight the efficacy of meta-heuristic algorithms in optimizing complex control systems, providing valuable insights for future research and practical applications, thereby contributing to the advancement of control systems engineering.

In order to investigate the honeybee population dynamics, many differential equation models were proposed. Fractional derivatives incorporate the history of the honeybee population dynamics. We numerically study the inverse problem of parameter identification in models with Caputo and Caputo–Fabrizio differential operators. We use a gradient method of minimizing a quadratic cost functional. We analyze and compare results for the integer (classic) and fractional models. The present work also contains discussion on the efficiency of the numerical methods used. Computational tests with realistic data were performed and are discussed. [ABSTRACT FROM AUTHOR]

In order to investigate the honeybee population dynamics, many differential equation models were proposed. Fractional derivatives incorporate the history of the honeybee population dynamics. We numerically study the inverse problem of parameter identification in models with Caputo and Caputo–Fabrizio differential operators. We use a gradient method of minimizing a quadratic cost functional. We analyze and compare results for the integer (classic) and fractional models. The present work also contains discussion on the efficiency of the numerical methods used. Computational tests with realistic data were performed and are discussed.

This paper has presented improved control structure based direct power control (DPC) applied for shunt active power filtering. Basically, DPC control strategy employs instantaneous active and reactive power terms as controlled variables. This work introduces an integration concept of predictive control algorithm for shunt active power filter system application. Process of this latter adopts discrete model of PWM converter in the aim to predict future behaviour of the system. Switching vector selection principles for predictive control is very different compared to conventional method. For conventional DPC the selection is performed via heuristic switching table while predictive DPC algorithm takes on an optimized way based on cost function minimization depending to power errors, this latter evaluate the effects of each active voltage vector and the one reducing the cost function is chosen to be applied in the next sampling period. The application of optimal switching state leads to regulate the input active and reactive power which resulted in the cancellation of harmonic power component contained in the network. Simulation results are presented to verify the validity and effectiveness of the proposed predictive DPC in terms of dynamic and steady state performance for shunt active power filtering application. [ABSTRACT FROM AUTHOR]

In this paper, a novel application of Finite Element Update Method (FEUM) is proposed for the inverse identification of material constitutive parameters in transversely isotropic laminates. Two-dimensional Digital Image Correlation (2D-DIC) is used for full-field measurements which is required for the identification process. Instead of measuring the in-plane displacements, which is a well-known application of 2D-DIC, we seek to measure the pseudo-displacements resulting from out-of-plane (towards camera) deflection of plate under a point load. These pseudo-displacements are basically the perspective projection of the three dimensional displacement fields on the image-plane of the image acquisition system. The cost function in this method is defined in terms of these projections instead of the true displacements - and hence the name Projected Finite Element Update Method (PFEUM). In this article, identification of in-plane elastic moduli of Carbon Fiber Reinforced Plastic (CFRP) plate has been performed using plate bending experiments which show pre-dominantly out-of-plane deflection with little contribution from the in-plane displacements. Identification results are validated by direct experimental measurements of the unknown elastic constants as well as theoretical estimates based on volume ratio of constituents. The results show good conformance between estimated and target values for at least three material parameters namely E, E and G. Effects of experimental noise on parameter estimates has also been evaluated to explain the observed deviation in estimated parameters with current test configuration. [ABSTRACT FROM AUTHOR]

A new type of dual-line multiprobe reflectometer, featuring an ultra-wideband operational bandwidth, is proposed. The presented reflectometer is composed of two parallel transmission lines along which weakly coupled probes are arranged. By utilization of two separate transmission lines, the minimum distance between two consecutive probes can be smaller than the length of a single probe, which allows for a highly nonuniform probes’ arrangement required to ensure ultra-wideband operation. Moreover, an efficient algorithm for the probes’ arrangement ensuring maximization of reflectometer’s bandwidth is proposed. The proposed concept has been validated by the design of an ultra-wideband dual-line multiprobe reflectometer having six probes and operating frequency range over 0.1–12 GHz. The obtained results are in a very good agreement with the reference values measured using a commercial VNA. [ABSTRACT FROM PUBLISHER]

A computationally efficient phase shift estimation algorithm is proposed for two-step phase-shifting interferometry based on a cost function minimization technique. The proposed method can accurately estimate the phase shift over a wide range resulting in reliable phase estimation. Due to the analytical solution offered by the proposed method, its computational efficiency is found to be higher than the existing state-of-art methods. While the performance of some methods is user-defined parameter-dependent, the proposed method is non-parametric and user-independent. The accuracy of phase shift and subsequent phase estimation using the proposed algorithm is found to be maximum around phase shift of π / 2 rad which further decreases for the phase shift values closer to 0 rad and π rad. The experimental results demonstrate the practical applicability of the proposed method. • Cost function minimization-based phase shift estimation in two-step phase shifting interferometry is proposed. • Performance comparison with state-of-art methods is provided. • The proposed method is noise robust and accurate. • The proposed method is computationally efficient compared to state-of-art methods. [ABSTRACT FROM AUTHOR]

This paper proposed an online optimizing duty cycle control approach for three-phase active-front-end rectifiers, aiming to obtain the optimal control actions under different operating conditions. Similar to finite-control set model predictive control strategy, a cost function previously constructed based on the desired control performance is adopted here, which is essential for the solving process of the optimizing problem. On the other hand, differently, with respect to the proposed strategy, duty cycle signals are optimized, instead of possible switching states. The determination of optimal duty cycles is made by predicting the effect of duty cycles on instantaneous current variations and minimizing the cost function. Due to the adoption of behavior prediction, the proposed controller inherits the excellent dynamic characteristics of predictive controllers. Moreover, the application of optimal duty cycles determined by cost function minimization automatically ensures optimum operations of converters within each sampling period. Improved transient and steady-state features of the proposed strategy are confirmed by experimental validations and in-depth comparisons with linear controllers, deadbeat predictive controllers, and finite-control set model predictive control strategies. [ABSTRACT FROM PUBLISHER]

A predictive current control strategy can realize flexible regulation of three-phase grid-tied converters based on system behaviour prediction and cost function minimization. However, when the predictive current control strategy with conventional switching patterns is adopted, the predicted duration time for voltage vectors turns out to be negative in some cases, especially under the conditions of bidirectional power flows and transient situations, leading to system performance deteriorations. This paper aims to clarify the real reason for this phenomenon under bidirectional power flows, i.e., rectifier mode and inverter mode, and, furthermore, seeks to propose effective solutions. A detailed analysis of instantaneous current variations under different conditions was conducted. An enhanced predictive current control strategy with improved switching patterns was then proposed. An experimental platform was built based on a commercial converter produced by Danfoss, and moreover, relative experiments were carried out, confirming the superiority of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this paper, a predictive direct power control (DPC) method without sector information and voltage vector selection is proposed for three-phase grid-connected converters. Different from conventional predictive direct power controllers, the proposed strategy always adopts fixed voltage vectors, instead of selecting voltage vectors according to the angular information of the grid-voltage vector or the virtual-flux vector. The converter switching time is obtained by minimizing the squared errors of the instantaneous active and reactive power. Switch duty cycles are then calculated and equivalently reconstructed. The proposed strategy not only presents rapid dynamic response due to the use of the predictive controller, but also possesses excellent steady-state performance as a result of duty cycle reconstruction. The main advantage of the proposed control scheme, compared with the classical DPC strategies, is that it is unnecessary to use sector information of the grid-voltage vector, and selection of active voltage vectors is also not required here. Therefore, incorrect selection of voltage vectors and the resulting performance deterioration are surely avoided, without the need of any additional compensation measures. An in-depth comparison and experimental assessment are given to validate the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper presents a 3-D shape reconstruction algorithm based on the level set method. Multiple dielectric and non-overlapping objects are considered. The level set algorithm is a gradient-type optimization approach that aims to minimize a cost function between measurements and computer-simulated data. The algorithm is capable of retrieving the shape and location of multiple targets made of two different and slightly lossy materials. An appropriate form of the deformation velocity based on the forward and adjoint fields is calculated. The method of moment surface integral equation is implemented to calculate the deformation velocity of the evolving objects. Two sets of Hamilton-Jacobi equations, associated with the two dielectric materials, are solved simultaneously to update the evolving objects. During the inversion scheme, the marching cubes method is employed to restore the surface meshes necessary for the forward solver. The algorithm is tested on corrupted synthetic data with signal-to-noise ratio of 10 dB. [ABSTRACT FROM AUTHOR]

Error concealment techniques are very important for video communication since compressed video sequences may be corrupted or lost when transmitted over error-prone networks. In this paper, we propose a novel two-stage error concealment scheme for erroneously received video sequences. In the first stage, we propose a novel spatio-temporal boundary matching algorithm (STBMA) to reconstruct the lost motion vectors (MV). A well defined cost function is introduced which exploits both spatial and temporal smoothness properties of video signals. By minimizing the cost function, the MV of each lost macroblock (MB) is recovered and the corresponding reference MB in the reference frame is obtained using this MV. In the second stage, instead of directly copying the reference MB as the final recovered pixel values, we use a novel partial differential equation (PDE) based algorithm to refine the reconstruction. We minimize, in a weighted manner, the difference between the gradient field of the reconstructed MB in current frame and that of the reference MB in the reference frame under given boundary condition. A weighting factor is used to control the regulation level according to the local blockiness degree. With this algorithm, the annoying blocking artifacts are effectively reduced while the structures of the reference MB are well preserved. Compared with the error concealment feature implemented in the H.264 reference software, our algorithm is able to achieve significantly higher PSNR as well as better visual quality. [ABSTRACT FROM PUBLISHER]

A constant modulus (CM)-based channel estimation scheme for space-time block-coded M-PSK and M-QAM transmission systems is derived. Exploiting the orthogonal structure of the space-time block coded transmission model, the analytical solutions to minimize the CM cost function are given for 2k PSK (k>2) and 22k-QAM schemes, and used to derive the expressions for the CM-based channel estimators. Illustrative results on the performance are presented. [ABSTRACT FROM PUBLISHER]