Wyniki wyszukiwania - BazTech

1

Current ripple reduction for finite control set model predictive control strategy of grid-tied inverter with reference current compensation

Jin Nan, Fan Wuchuang, Fang Jie, Wu Jie, Shen Yongpeng

Archives of Electrical Engineering

|

2023

|

Vol. 72, nr 1

5--22

EN

In the finite control set model predictive control (FCS-MPC) strategy of the grid-tied inverter, the current ripple (CR) affects the selection of optimal voltage vectors, which leads to the increase of output current ripples. In order to solve this problem, this paper proposes a CR reduction method based on reference current compensation (RCC) for the FCS-MPC strategy of grid-tied inverters. Firstly, the influence of the CR on optimal voltage vector selection is analyzed. The conventional CR prediction method is improved, which uses inverter output voltage and grid voltage to calculate current ripples based on the space state equation. It makes up for the shortcomings that the conventional CR prediction method cannot predict in some switching states. The improved CR method is more suitable for the FCS-MPC strategy. In addition, the differences between the two cost functions are compared through visual analysis. It is found that the sensitivity of the square cost function to small errors is better than that of the absolute value function. Finally, the predicted CR is used to compensate the reference current. The compensated reference current is substituted into the square cost function to reduce the CR. The experimental results show that the proposed method reduces the CR by 47.3%. The total harmonic distortion (THD) of output current is reduced from 3.86% to 2.96%.

2

Single-source three-phase switched-capacitor-based MLI

Jena Kasinath, Gupta Krishna Kumar, Bhatnagar Pallavee, Jain Sanjay K., Stala Robert, Waradzyn Zbigniew, Piróg Stanisław, Penczek Adam, Mondzik Andrzej, Skała Aleksander

Power Electronics and Drives

|

2022

|

Vol. 7 (42)

197--209

EN

This article proposes a novel three-phase inverter based on the concept of switched capacitors (SCs), which uses a single DC source. A three-phase, seven-level line-to-line output voltage waveform is synthesised by the proposed topology, which includes eight switches, two capacitors, and one diode per phase leg. The proposed topology offers advantages in terms of inherent voltage gain, lower voltage stresses on power switches, and a reduced number of switching components. Additionally, the switched capacitors are self-balanced, thereby eliminating the need for a separate balancing circuit. The proposed structure and its operating principle, the self-balancing mechanism of the capacitors, and the control strategy are all thoroughly explained in the article. The proposed topology has also been compared with some recent SC topologies. Lastly, the proposed topology has been shown to be feasible through simulation and experimentation.

3

Research on reliability allocation strategy for gear transmission system of high-speed train

Ai Yibo, Cui Peng, Li Yuanyuan, Zhang Weidong

Eksploatacja i Niezawodność

|

2022

|

Vol. 24, no. 3

574--582

EN

High-speed train industry is in the stage of rapid development, and the reliability allocation strategy is helpful to improve the reliability of the system and reduce the economic cost of components. In this paper, the reliability allocation of gearbox transmission system of highspeed train is studied. Combining AGREE allocation method and reliability allocation method based on cost function, the reliability allocation of high-speed train gear transmission system is carried out. Considering the quantity, importance, cost and complexity of various parts of high-speed train gear transmission system, the feasibility factor of improving reliability based on the cost function allocation method was improved to acquire the improved cost function, and the reliability optimization allocation model based on the improved cost function was established. Compared with AGREE allocation method and the traditional allocation method based on cost function, the improved optimization allocation strategy proposed in this paper is more suitable for high-speed train gear transmission system.

4

A New 13-Level Switched-Capacitor Inverter with Reduced Device Count

Jena Kasinath, Panigrahi Chinmoy Kumar, Gupta Krishna Kumar

Power Electronics and Drives

|

2021

|

Vol. 6 (41)

26--41

EN

This paper proposed a new voltage-boosting 13-level switched-capacitor (SC) cost-effective inverter. The proposed topology comprises fourteen transistors, three capacitors and a single DC source to produce a 13-level staircase waveform. The capacitor voltage balancing problem is inherently solved by the series/parallel technique. Structural description, working principle, calculation of optimum values of capacitance and modulation scheme are briefly described. The comparative analyses with the existing SC multilevel inverter (MLI) in terms of voltage gain, blocking voltage, total standing voltage (TSV), component per level factor and cost function illustrate the merits of the proposed topology. Further, simulation and experimental results at different loading conditions verify the feasibility of the proposed topology.

5

Path planning for an autonomous underwater vehicle in a cluttered underwater environment based on the heat method

Sun Kaiyue, Liu Xiangyang

International Journal of Applied Mathematics and Computer Science

|

2021

|

Vol. 31, no. 2

289--301

EN

This paper proposes a novel autonomous underwater vehicle path planning algorithm in a cluttered underwater environment based on the heat method. The algorithm calculates the isotropic and anisotropic geodesic distances by adding the direction and magnitude of the currents to the heat method, which is named the anisotropy-based heat method. Taking account of the relevant influence of the environment on the cost functions, such as currents, obstacles and turn of the vehicle, an efficient collision-free and energy-optimized path solution can be obtained. Simulation results show that the anisotropy-based heat method is able to find a good trajectory in both static and dynamic clutter fields (including uncertain obstacles and changing currents). Compared with the fast marching (FM) algorithm, the anisotropy-based heat method is not only robust, flexible, and simple to implement, but it also greatly saves time consumption and memory footprint in a time-variant environment. Finally, the evaluation criteria of paths are proposed in terms of length, arrival time, energy consumption, and smoothness.

6

Objectives of an enterprise. Bi-criteria analysis and negotiation problems

Gadomski Jan, Kruś Lech

Control and Cybernetics

|

2021

|

Vol. 50, No. 1

169--193

EN

A decision-making process is considered for a firm, in which two coexisting groups of interests pursue different goals. An original model based on a non-neoclassical production function is proposed. The function satisfies the conditions formulated by R. Frisch, which makes it possible to investigate firms operating in the environment far from the perfect competition and pursuing goals other than profit maximization. A two-criteria optimization problem is formulated with the two criteria representing the goals of the groups: maximization of profit and maximization of income generated by the firm with respect to capital and labor. The problem is considered in two variants of the product market, namely the perfect and the imperfect competition. Solutions of the problem are analyzed including the derived Pareto sets. The importance of knowledge about the Pareto set in negotiations between the groups of interests in the firm is illustrated and discussed.

7

Novel anchor-selection scheme for distributed mobility management

Davaasambuu Battulga, Telmuun Tumnee, Sasko Dominik, Keping Yu, Sodbileg Shirmen

Computer Science

|

2021

|

T. 22 (1)

143–163

EN

The number of subscribers in mobile networks is growing rapidly, which challenges network management and data delivery. Efficient management and routing are key solutions. One important solution is distributed mobility management (DMM), which handles the mobility of subscribers at the edges of mobile networks and load balancing. Otherwise, mobility anchors are distributed across a network that can manage the handover procedures. In this paper, we propose a novel mobility anchor-selection scheme based on the results of a cost function with three factors to select a suitable cell as well as an anchor for moving subscribers and improving the handover performances of networks. Our results illustrate that the proposed scheme provides significantly enhanced handover performance.

8

Experimental Study of Totally Optimal Decision Trees

Aldilaijan Abdulla, Azad Mohammad, Moshkov Mikhail

Fundamenta Informaticae

|

2019

|

Vol. 165, nr 3-4

245--261

EN

In this paper, we present results of experimental studies related to the existence of totally optimal decision trees (which are optimal relative to two or more cost functions simultaneously) for nine decision tables from the UCI Machine Learning Repository. Such trees can be useful when we consider decision trees as algorithms for problem solving or as a way for knowledge representation. For cost functions, we use depth, average depth, and number of nodes. We study not only exact but also approximate decision trees based on five uncertainty measures: entropy, Gini index, misclassification error, relative misclassification error, and number of unordered pairs of rows with different decisions. To investigate the existence of totally optimal trees, we use an extension of dynamic programming that allows us to make multi-stage optimization of decision trees relative to a sequence of cost functions. Experimental results show that totally optimal decision trees exist in many cases. The behavior of graphs that describe how the number of decision tables with totally optimal decision trees depends on their accuracy is mainly irregular. However, one can observe some trends, in particular, an upward trend when accuracy is decreasing.

9

Study on uncertainty of inversion and resolution limit in the presence of noise

Luo C., Wang S., Yuan S.

Acta Geophysica

|

2018

|

Vol. 66, no. 5

1011--1018

EN

This study analyzed the uncertainty of inversion and the resolution limit in the presence of noise by means of statistical experiments. The exhaustive method is adopted to obtain the global optimal solution in each experiment. We found that even with small level of noise, solutions fluctuate in a large range for the thin bed. The distribution of solutions in the presence of noise is closely related to the spread of the cost function in the absence of noise. As a result, the area of a certain neighborhood around the true solution on the spread of the cost function in the absence of noise is used to evaluate the uncertainty of inversion and the resolution limit in the presence of noise. In the case that the SNR (signal-to-noise ratio) is 5 in this study, solutions focus around the true solution with a very small uncertainty only when the bed thickness is greater than the reciprocal of the double predominant frequency of the convoluting wavelet.

10

Modified scheme of predictive torque control for three-phase four-switch inverter-fed motor drive with adaptive DC-link voltage imbalance suppression

Sobański P.

Power Electronics and Drives

|

2017

|

Vol. 2 (37), No. 2

93--101

EN

Classical voltage space vector modulation techniques cannot be efficiently applied in four-switch three-phase voltage inverter-fed electrical drives due to a voltage offset in DC-link capacitors. The capacitor voltages imbalance is a result of a bidirectional current which flows in a phase of an electric motor that is connected to a DC-link capacitor midpoint. To overcome this problem which leads to an incorrect inverter voltage modulation or even can affect the DC-link capacitors, predictive control algorithms considering the voltage offset in DC-link capacitors have been developed. Despite the predictive methods are highly effective, they require to adjust the cost function weighting factors which is normally an inexplicit task. In this paper, an on-line tuning method of the weighting factor related to the capacitor voltages imbalance incorporated in the cost function of the predictive algorithm has been proposed. According to the proposed approach, the weighting factor is self-adjusted so that the DC-link capacitor voltages are stabilized as well as a high quality of the drive control is remained simultaneously, regardless of its operating point. The proposed strategy has been validated by using simulation model of the induction motor drive system.

11

Algebraic Riccati equation based Q and R matrices selection algorithm for optimal LQR applied to tracking control of 3rd order magnetic levitation system

Kumar E V., Jerome J.

Archives of Electrical Engineering

|

2016

|

Vol. 65, nr 1

151-168

EN

This paper presents an analytical approach for solving the weighting matrices selection problem of a linear quadratic regulator (LQR) for the trajectory tracking application of a magnetic levitation system. One of the challenging problems in the design of LQR for tracking applications is the choice of Q and R matrices. Conventionally, the weights of a LQR controller are chosen based on a trial and error approach to determine the optimum state feedback controller gains. However, it is often time consuming and tedious to tune the controller gains via a trial and error method. To address this problem, by utilizing the relation between the algebraic Riccati equation (ARE) and the Lagrangian optimization principle, an analytical methodology for selecting the elements of Q and R matrices has been formulated. The novelty of the methodology is the emphasis on the synthesis of time domain design specifications for the formulation of the cost function of LQR, which directly translates the system requirement into a cost function so that the optimal performance can be obtained via a systematic approach. The efficacy of the proposed methodology is tested on the benchmark Quanser magnetic levitation system and a detailed simulation and experimental results are presented. Experimental results prove that the proposed methodology not only provides a systematic way of selecting the weighting matrices but also significantly improves the tracking performance of the system.

12

An image segmentation method to reveal regions of stress manifestation in stained cucurbits' leaves using LVQ neural network

Gocławski J., Sekulska-Nalewajko J.

Automatyka / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

|

2011

|

T. 15, z. 3

105-118

EN

In the paper an image segmentation method has been presented, which enables to detect cucurbits' leaves stress manifestation featured by the accumulation of reactive oxygen species (ROS) like hydrogen peroxide (H2O2) or superoxide anion radical (O2 ). After specific leaf staining the regions can be distinguished in colour space from the intact leaf parts. The proposed algorithm, developed in MATLAB environment, includes the segmentation of scanned leaf images with selected background, the exclusion of certain leaf parts and the classification of reminded leaf blade image pixels in H, S (hue, saturation) colour space. The classification is based on LVQ type neural network with several neurons in an internal layer and two neurons in an output layer, which represent image pixels of stained and unstained tissue respectively. The network learning process uses representative leaf image pixel data and binary template images of stress manifestation regions prepared manually by specialists. The classifier was 5-fold cross validated with the pixel H, S data of learned image and validated with the data of other images (with templates). The computed classification errors have been included. The experiments of stress regions detection carried out for the series of 12 images gave a few percent errors compared to manual classification.

PL

W artykule przedstawiono metodę segmentacji obrazów, która pozwala wykrywać obszary ujawniania się stresu na liściach roślin dyniowatych charakteryzujących się akumulacją reaktywnych form tlenu (ROS), takich jak woda utleniona (H2O2) lub anionorodnik ponadtlenkowy (O2). W następstwie specyficznego wybarwiania obszary te dają się odróżnić od nietkniętych części liścia w przestrzeni koloru. Proponowany algorytm, opracowany w środowisku MATLAB, obejmuje segmentację obrazów liści zeskanowanych na wybranym tle, wyłączanie pewnych partii liścia z dalszej analizy i klasyfikację pozostałych pikseli obrazu blaszki liścia w przestrzeni H, S (odcień, nasycenie). Klasyfikacja bazuje na sieci neuronowej typu LVQ z kilkoma neuronami w warstwie wewnętrznej i dwoma neuronami warstwy wyjściowej, reprezentującymi piksele obrazu odpowiadające wybarwionej i niewybarwionej tkance liścia. Proces uczenia się sieci wykorzystuje dane pikseli reprezentatywnych obrazów i binarne wzorce klasyfikacji obszarów ujawniania stresu przygotowane manualnie przez specjalistów. Klasyfikator poddano 5-krotnej ocenie krzyżowej dla danych H, S obrazu podlegającego uczeniu się i oceniono dla danych z innych obrazów (mających wzorce). Dołączono obliczone błędy klasyfikacji. Eksperymenty wykrywania obszarów stresu przeprowadzone dla serii 12 obrazów dały kilkuprocentowe błędy w porównaniu z klasyfikacją manualną.

13

An algorithm to extract first and second order venation of apple-tree leaves stained for H2O2 detection

Sekulska-Nalewajko J., Gocławski J., Gajewska E., Wielanek M.

Automatyka / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

|

2010

|

T. 14, z. 3/1

359-372

EN

In the paper an algorithm for the extraction of first and second order leaf venation has been presented. The algorithm applies to apple tree leaves specially stained to reveal the areas of H2O2 appearing in the leaf blade as brown spots of different size and intensity. In the considered case they represent the defence reaction of planfs tissue to a bacterial infection called fire blight. Examined leaf images include visible leaf veins with colour hue and brightness similar to the H2O2 spots. They are often superimposed on leaf veins and make serious distortions for the process of their extraction. In these conditions typical algorithms for the detection of venation patterns usually fail, so a new method of primary and secondary veins detection has been proposed. The vein extraction is based on the step-wise tracking of each vein axis using polygonal linę with the line segments of fixed size. The optimal direction for each step is obtained through the minimization of the proposed cost function depending on the prediction angle. The algorithm has been written in the M-language and executed in MATLAB environment. The experiments of leaf vein tracking carried out for the series of images gave promising results accepted by the biologists.

PL

W artykule przedstawiono algorytm wykrywania pierwszo- i drugorzędowego użyłkowania liści. Algorytm ten zastosowano do liści jabłoni specjalnie barwionych pod kątem wykrycia obszarów H2O2, występujących w blaszce liściowej w postaci brązowych plam o różnym rozmiarze i natężeniu barwy. Plamy te są objawem reakcji obronnej tkanki roślinnej na infekcję bakteryjną zwaną zarazą ogniową. Badane obrazy liści zawierają widoczne żyłki, których odcień koloru oraz jasności są zbliżone do tych obserwowanych w obszarach koncentracji H2O2. Obszary te często nakładając się na żyłki liścia, stanowią poważne zakłócenia w procesie ich wykrywania. W tych warunkach typowe algorytmy identyfikacji wzoru unerwienia zazwyczaj nie sprawdzają się, dlatego zaproponowano nową metodę detekcji żyłkowania pierwszego i drugiego rządu. Jest ona oparta na krokowym śledzeniu każdej żyłki z wykorzystaniem linii łamanej o odcinkach stałej długości. Optymalny kierunek w każdym kroku śledzenia uzyskuje się poprzez minimalizację zaproponowanej funkcji kosztu względem kąta predykcji. Algorytm napisano w języku M i zrealizowano w środowisku MATLAB. Testy algorytmu śledzenia żyłek przeprowadzone dla serii obrazów dają obiecujące rezultaty zaakceptowane przez biologów.

14

Multicriterial optimization of the asynchronous machine

Sames M., Chrobacek K.

Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały

|

2008

|

Vol. 62, nr 28

138-143

EN

The goal of our work is to apply an optimization algorithm to design asynchronous machine and improve several output parameters simultaneously. Such optimization is called multicriterial optimization. We are looking to find compromise design with the best (at least to keep the original) output parameters and the lowest production cost. The model makes possible to compute all output parameters important for optimization which are used in optimization procedure. We have chosen the weighting method that deals with weights as the significance of output parameters. The cost function to be maximized (to reach the best output variables) is assembled and optimization algorithm applied. Because of the cost function's shape the random optimization algorithm has been chosen.

PL

Praca dotyczy wykorzystanie algorytmów optymalizacyjnych przy projektowaniu maszyn asynchronicznych. Maszyna optymalizowana jest tak, by zachowane były ważne parametry pierwotne maszyny (sprawność, współczynnik mocy), przy minimalnych kosztach materiałów. Koszt maszyny obliczany jest z masy oraz średnich kosztów aktywnych podzespołów maszyny. Optymalizacja zawiera śledzenie nagrzewania się statora, które obliczamy za pomocą strat oraz współczynników empirycznych uzyskanych z pomiarów. Optymalizację nazywano wielokryterialną, ponieważ śledzi ona siedem wybranych parametrów wyjściowych równocześnie. Do zestawienia wartości fitness wykorzystano metodę wagową z dogodnymi funkcjami normującymi, których zaletą jest proste nastawianie ważności poszczególnych parametrów. Algorytm optymalizacji dobrano z uwzględnieniem charakteru badanego przebiegu oraz wymagań na czas rozwiązania. Wykorzystano jedną z metod wyszukiwania przypadkowego, algorytm MCRS (Modified Control Random Search), który bazuje na metodzie simpleks zaprojektowanej przez naszych kolegów z uniwersytetu. Zoptymalizowana maszyna na podstawie dobranych postulatów zachowuje wszystkie ważne parametry wyjściowe i jednocześnie wykazuje niższe koszty dzięki odpowiedniemu doborowi zmiennych projektowych oraz funkcji normowania i wag.

15

Recognition of partially occluded shapes using a neural optimization network

Banerjee B.

Machine Graphics and Vision

|

2004

|

Vol. 13, No. 1/2

3-23

EN

The current work presents an algorithm for recognition of partially occliided shapes in a cluttered scene The images are represented by a sequence of angles subtended at the corner points. The cost due to comparison between the input cluttered scene and the stored images is obtained from a cost function designed to storo the obtained information in the form of a cost matrix which is presented to the input of an optimization network. The parameters of the optimization network are determined so as, to minimize an energy function, the minima of which occur at the solutions of the problem. The results, as obtained in different domains (2D shapes and projected 3D shapes) with different degrees of occlusion, provide intereSting insights into the operation of the algorithm as well as avenues for future research.