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Decentralized aggregation and leader-following control of a swarm of quadcopters with nonlinear under-actuated dynamics
, Article Aerospace Science and Technology ; Volume 107 , December , 2020 ; Alasty, A ; Sharif University of Technology
Elsevier Masson S. R. L
2020
Abstract
This paper studies the decentralized control of a swarm of quadrotors on the basis of the nonlinear, highly-coupled, and under-actuated dynamic model of quadcopters. The swarm of quadcopters must illustrate the desired swarm behavior as fast as possible while collision avoidance is preserved during the entire evolution process. The interaction relationship among the swarm members is modeled by artificial potential functions and according to the nearest neighbor rule. The sliding mode control technique is employed to control the velocity of quadcopters in the swarm. Finally, two fundamental swarm behaviors, i.e. swarm aggregation and leader-following, are numerically simulated to demonstrate...
Modelling and Control of Swarm Robotic Systems with Multiple Ground and Aerial Clusters under an Imperfect Network
, Ph.D. Dissertation Sharif University of Technology ; Alasty, Aria (Supervisor)
Abstract
In this study, an effective collective control strategy is presented for the decentralized behavior control of a heterogeneous multi–cluster swarm robotic system composed of a group of quadrotors as aerial agents, and a group of two–wheeled mobile robots as ground agents. In this regard, first of all, a new element for swarm robotic systems is introduced. This element, which is made up of a portion of swarm members and encircles the whole swarm, is called the shell element. An algorithm for developing the shell element in swarm robotic systems composed of agents moving in the two–dimensional space is established. Subsequently, inspired by the thermodynamic science and based on the introduced...
Introducing shell formation and a thermodynamics-inspired concept for swarm robotic systems
, Article Robotics and Autonomous Systems ; Volume 148 , 2022 ; 09218890 (ISSN) ; Alasty, A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this article, a new formation for swarm robotic systems is introduced. This formation, which is made up of a portion of swarm members and encircles the whole swarm, is called the shell formation. In this regard, an effective algorithm for developing the shell formation in swarm robotic systems is established. The interaction mechanism among swarm agents is based on the method of artificial potential fields and the local rule of the nearest neighbor. Subsequently, inspired by the thermodynamic science and based on the introduced shell formation, the thermodynamic concept of pressure is generalized to swarm robotic systems. Finally, the efficacy of the introduced shell formation in solving...
Decentralized leader-following control of a heterogeneous swarm robotic system subject to network-induced imperfections
, Article Unmanned Systems ; 2023 ; 23013850 (ISSN) ; Alasty, A ; Sharif University of Technology
World Scientific
2023
Abstract
This paper studies the decentralized leader-following control of a heterogeneous swarm robotic system composed of a group of quadrotors as aerial agents, and a group of two-wheeled mobile robots as ground agents. The interaction mechanism between the agents is based on the method of artificial potential fields. While the agents in the aerial and ground sub-swarms communicate with each other through local and direct vision, the information exchange between the aerial and ground sub-swarms is established through a wireless network. The control system of ground and aerial agents is designed using the sliding mode control technique. The controller proposed for quadrotors is finite-time,...
Vibration band gap properties of a periodic beam-like structure using the combination of GDQ and GDQR methods
, Article Waves in Random and Complex Media ; 2019 ; 17455030 (ISSN) ; Mahdian Parrany, A ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters....
Vibration band gap properties of a periodic beam-like structure using the combination of GDQ and GDQR methods
, Article Waves in Random and Complex Media ; 2019 ; 17455030 (ISSN) ; Mahdian Parrany, A ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters....
Vibration band gap properties of a periodic beam-like structure using the combination of GDQ and GDQR methods
, Article Waves in Random and Complex Media ; Volume 31, Issue 5 , 2021 , Pages 795-811 ; 17455030 (ISSN) ; Mahdian Parrany, A ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters....
Sudoku rectangle completion (Extended Abstract)
, Article Electronic Notes in Discrete Mathematics ; Volume 49 , November , 2015 , Pages 747-755 ; 15710653 (ISSN) ; Mahmoodian, E. S ; Sharif University of Technology
Elsevier
2015
Abstract
Over the last decade, Sudoku, a combinatorial number-placement puzzle, has become a favorite pastimes of many all around the world. In this puzzle, the task is to complete a partially filled 9 × 9 square with numbers 1 through 9, subject to the constraint that each number must appear once in each row, each column, and each of the nine 3 × 3 blocks. Sudoku squares can be considered a subclass of the well-studied class of Latin squares. In this paper, we study natural extensions of a classical result on Latin square completion to Sudoku squares. Furthermore, we use the procedure developed in the proof to obtain asymptotic bounds on the number of Sudoku squares of order n
CFD Modeling of a LNG Microchannel Heat Exchanger
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor)
Abstract
In the present work, the possibility of using a cross flow microchannel heat exchanger in cryogenic service for natural gas liquefaction has been numerically investigated using 3D computational fluid dynamics approach. Microchannels of rectangular and triangular cross section with a hydraulic diameter of 0.667 and 0.472 mm respectively have been constructed in Gambit and Fluent is used as the solver of numerical simulations.For solver’s equations validation, the existing experimental data on flow of water through rectangular microchannels has been modeled by CFD. Comparison of CFD results with experimental data shows a good agreement.Both models are constructed of three distinct layers. In...
Separation of speech sources in under-determined case using SCA and time-frequency methods
, Article 2008 International Symposium on Telecommunications, IST 2008, Tehran, 27 August 2008 through 28 August 2008 ; 2008 , Pages 533-538 ; 9781424427512 (ISBN) ; Babaiezadeh, M ; Jutten, C ; Sharif University of Technology
2008
Abstract
This paper presents a new algorithm for Blind Source Separation (BSS) of Instantaneous speech mixtures in under-determined case. A demixing algorithm which exploits the sparsity of speech signals in the short time Fourier transform (STFT) domain is proposed. This algorithm combines the modified k-means clustering procedure involved in the Line Orientation Separation Technique (LOST) with Smoothed l0-norm minimization (SL0) method. First procedure along with a transformation into a sparse domain tries to estimate the mixing matrix, and the second method tries to extract the sources from the mixtures. Simulation results are presented and compared to the Degenerate Unmixing Estimation Technique...
On a conjecture of Keedwell and the cycle double cover conjecture
, Article Discrete Mathematics ; Volume 216, Issue 1-3 , 2000 , Pages 287-292 ; 0012365X (ISSN) ; Mahmoodian, E. S ; Saberi, A ; Salavatipour, M. R ; Tusserkani, R ; Sharif University of Technology
2000
Abstract
At the 16th British Combinatorial Conference (1997), Cameron introduced a new concept called 2-simultaneous coloring. He used this concept to reformulate a conjecture of Keedwell (1994) on the existence of critical partial latin squares of a given type. Using computer programs, we have verified the truth of the above conjecture (the SE conjecture) for all graphs having less than 29 edges. In this paper we prove that SE conjecture is a consequence of the well-known oriented cycle double cover conjecture. This connection helps us to prove that the SE conjecture is true for semieulerian graphs. © 2000 Elsevier Science B.V. All rights reserved
Robust backstepping control of an interlink converter in a hybrid AC/DC microgrid based on feedback linearisation method
, Article International Journal of Control ; 2016 , Pages 1-15 ; 00207179 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
This paper presents a robust dc-link voltage as well as a current control strategy for a bidirectional interlink converter (BIC) in a hybrid ac/dc microgrid. To enhance the dc-bus voltage control, conventional methods strive to measure and feedforward the load or source power in the dc-bus control scheme. However, the conventional feedforward-based approaches require remote measurement with communications. Moreover, conventional methods suffer from stability and performance issues, mainly due to the use of the small-signal-based control design method. To overcome these issues, in this paper, the power from DG units of the dc subgrid imposed on the BIC is considered an unmeasurable...
A backstepping high-order sliding mode voltage control strategy for an islanded microgrid with harmonic/interharmonic loads
, Article Control Engineering Practice ; Volume 58 , 2017 , Pages 150-160 ; 09670661 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
This paper presents a new nonlinear voltage control strategy based on backstepping control and a high-order sliding mode differentiator for an islanded microgrid. The microgrid consists of multiple distributed generation (DG) units with an arbitrary configuration that can be parametrically uncertain or topologically unknown. The proposed controller robustly regulates the microgrid voltages in the presence of parametric uncertainties, unmodeled dynamics, load imbalances, and nonlinear loads with harmonic/interharmonic currents. In contrast to existing methods, the controller does not need to know the frequency of harmonic and interharmonic current of microgrid loads that lead to the reduction...
Distributed robust finite-time secondary voltage and frequency control of islanded microgrids
, Article IEEE Transactions on Power Systems ; Volume 32, Issue 5 , 2017 , Pages 3648-3659 ; 08858950 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
2017
Abstract
This paper presents a distributed, robust, finite-time secondary control for both voltage and frequency restoration of an islanded microgrid with droop-controlled inverter-based distributed generators (DGs). The distributed cooperative secondary control is fully distributed (i.e., uses only the information of neighboring DGs that can communicate with one another through a sparse communication network). In contrast to existing distributed methods that require a detailed model of the system (such as line impedances, loads, other DG units parameters, and even the microgrid configuration, which are practically unknown), the proposed protocols are synthesized by considering the unmodeled...
A robust backstepping high-order sliding mode control strategy for grid-connected DG units with harmonic/interharmonic current compensation capability
, Article IEEE Transactions on Sustainable Energy ; Volume 8, Issue 2 , 2017 , Pages 561-572 ; 19493029 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
This paper presents a new nonlinear current control strategy based on backstepping control and high-order sliding mode differentiator in order to employ distributed generation (DG) unit interfacing converters to actively compensate harmonics/interharmonics of local loads. The converter-based DG unit is connected to a weak grid (with uncertain impedance) and local load (that can be parametrically uncertain and topologically unknown) through an LCL filter. The proposed strategy robustly regulates the inverter output currents and delivers pure sinusoidal, three-phase balanced currents to the grid. The new controller demonstrates the robust performance and robust stability of the DG unit system...
Fully distributed cooperative secondary frequency and voltage control of islanded microgrids
, Article IEEE Transactions on Energy Conversion ; Volume 32, Issue 2 , 2017 , Pages 675-685 ; 08858969 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
2017
Abstract
This paper proposes a new distributed cooperative secondary control for both frequency and voltage restoration of an islanded microgrid with droop-controlled, inverter-based distributed generations (DGs). Existing distributed methods commonly design secondary control based on the minimum real part of the nonzero Laplacian matrix eigenvalues related to the microgrid communication graph, which, however, is global information. In contrast to the existing distributed methods, in this paper we design a fully distributed adaptive control based on the dynamic model of DG units and on information from neighboring units. Therefore, the proposed control scheme increases the system reliability,...
Robust tuning of transient droop gains based on kharitonov's stability theorem in droopcontrolled microgrids
, Article IET Generation, Transmission and Distribution ; Volume 12, Issue 14 , 2018 , Pages 3495-3501 ; 17518687 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
2018
Abstract
This study addresses the robust stability analysis for an islanded microgrid with droop-controlled inverter-based distributed generators (DGs). Owing to large load changes, microgrid structure reconfiguration, and higher-power demands, the low-frequency (LF) dominant modes of a microgrid stir toward unstable zone and make the system more oscillatory or even unstable. In this study, a robust two-degree-of-freedom (2DOF) decentralised droop controller, which is the combination of the conventional droop with a robust transient droop function, is utilised for each inverter-based DG unit. Unlike conventional tuning of 2DOF droop controllers, a new design procedure is proposed to robustly...
Visibility testing and counting for uncertain segments
, Article Theoretical Computer Science ; Volume 779 , 2019 , Pages 1-7 ; 03043975 (ISSN) ; Alipour, S ; Ghodsi, M ; Mahdian, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
We study two well-known planar visibility problems, namely visibility testing and visibility counting, in a model where there is uncertainty about the input data. The standard versions of these problems are defined as follows: we are given a set S of n segments in R 2 , and we would like to preprocess S so that we can quickly answer queries of the form: is the given query segment s∈S visible from the given query point q∈R 2 (for visibility testing) and how many segments in S are visible from the given query point q∈R 2 (for visibility counting). In our model of uncertainty, each segment may or may not exist, and if it does, it is located in one of finitely many possible locations, given by a...
Voltage and frequency consensusability of autonomous microgrids over fading channels
, Article IEEE Transactions on Energy Conversion ; Volume 36, Issue 1 , 2021 , Pages 149-158 ; 08858969 (ISSN) ; Khorsandi, A ; Baghaee, H. R ; Sadati, N ; Shirvani Moghaddam, S ; Guerrero, J. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this article, a novel cooperative secondary voltage/frequency control considering time-varying delays and noises in fading channels is presented for an autonomous alternating current (AC) voltage sourced-based converter (VSC)-based microgrid (MG), including inverter-interfaced distributed generations (DGs). Fading phenomenon makes complex random fluctuations on the voltage and frequency of every DG received from its neighbor DGs. In multi-agent cooperative systems, in addition to the total additive noise and time-variant delay, a multiplicative complex random variable is considered to model the main received signal and its replicas due to multipath propagation. The proposed...
Length-Constrained path-matchings in graphs
, Article Networks ; Volume 39, Issue 4 , 2002 , Pages 210-215 ; 00283045 (ISSN) ; Hajiaghayi, M. T ; Mahdian, M ; Mirrokni, V. S ; Sharif University of Technology
2002
Abstract
The path-matching problem is to find a set of vertex- or edge-disjoint paths with length constraints in a given graph with a given set of endpoints. This problem has several applications in broadcasting and multicasting in computer networks. In this paper, we study the algorithmic complexity of different cases of this problem. In each case, we either provide a polynomial-time algorithm or prove that the problem is NP-complete. © 2002 Wiley Periodicals, Inc