Loading...
Search for: time-stability
0.006 seconds

    A chattering-free finite-time robust synchronization scheme for uncertain chaotic systems

    , Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 43 , 2019 , Pages 995-1003 ; 22286187 (ISSN) Heidarzadeh, S ; Salarieh, H ; Sharif University of Technology
    Springer International Publishing  2019
    Abstract
    This paper addresses a simple chattering-free and finite-time convergent robust synchronization scheme for a general class of disturbed master and slave chaotic systems. Unlike traditional variable structure control schemes, the proposed controller does not directly include a switching function, and chattering is avoided. The term including switching function is the input of a low-pass filter where the filtered output is used in the controller. Also, numerical differentiation of master and slave state trajectories is not required to implement the controller. Stability of the proposed controller is established using a Lyapunov stability analysis and the finite-time convergence theories.... 

    Finite-Time guidance laws for landing process of a spacecraft subjected to disturbances

    , Article 2016 4th International Conference on Control, Instrumentation, and Automation, ICCIA 2016, 27 January 2016 through 28 January 2016 ; 2016 , Pages 296-300 ; 9781467387040 (ISBN) Abooee, A ; Moravej Khorasani, M ; Haeri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    This paper investigates the finite-Time landing of a spacecraft on a celestial target subjected to disturbances and air drag forces. Based on nonsingular fast terminal sliding mode control, a novel guidance law is designed to accomplish the landing goal within a specified finite time while the upper bound of disturbances is assumed to be known. Finally, a numerical example of the spacecraft landing problem is simulated by applying the proposed scheme. The obtained results illustrate that the designed guidance law can achieve the landing goal in the specified finite time  

    Control Design for Nonlinear Stochastic Processes in the Presence of Input Constraint

    , M.Sc. Thesis Sharif University of Technology Mozaffari Bezi, Ali (Author) ; Shahrokhi, Mohammad (Supervisor)
    Abstract
    Due to the presence of a random variable in the process dynamics or due to the presence of measurement noise, many processes have stochastic in nature. Behaviors of these processes are different from the deterministic processes and therefore their controllers are also different. The aim of this research is to design adaptive controller for stochastic processes with a non-strict feedback structure and in the presence of input constraints. Also, the considered system has other limitations such as the unmeasured states, actuator failure, unknown dynamics and fixed time stability is desired. The input limitation can be caused by the limitation of the final control element, because the input... 

    Free-chattering robust finite time tracking for connected double integrator nonlinear systems

    , Article 2016 4th International Conference on Control, Instrumentation, and Automation, ICCIA 2016, 27 January 2016 through 28 January 2016 ; 2016 , Pages 301-306 ; 9781467387040 (ISBN) Abooee, A ; Moravej Khorasani, M ; Haeri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    In this paper, a new form of generalized nonsingular fast terminal sliding mode control approach is proposed to provide the finite time tracking in connected chain of double integrator nonlinear systems subjected to additive bounded unknown uncertainties, disturbances, and internal interactions. The proposed approach presents an adjustable finite time for achieving the tracking goal which is a summation of two separate tunable times including finite reaching time and finite settling time. Tuning of the total finite time is done by adjusting arbitrary parameters in the control inputs and sliding surfaces. The high frequency switching of the control method is removed by applying a second order... 

    A new fast finite time fractional order adaptive sliding-mode control for a quadrotor

    , Article 7th International Conference on Control, Instrumentation and Automation, ICCIA 2021, 23 February 2021 through 24 February 2021 ; 2021 ; 9780738124056 (ISBN) Naderi Soorki, M ; Vedadi Moghaddam, T ; Emamifard, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Fast finite time adaptive sliding mode control of a quadrotor in the presence of uncertainties and unbounded external disturbances is dealt in this paper. To this end, a fractional order sliding surface is first defined and then, an adaptive sliding mode controller is designed to guarantee finite time stability with fast convergence of quadrotor states to the desired trajectory. In this controller, it is assumed that the upper bound of the model uncertainties and external disturbances is a nonlinear function with unknown coefficients. These coefficients are estimated via stable adaptive laws. Finite time stability of the closed-loop system is analyzed using Lyapunov theorem. Simulation... 

    Prescribed-Time control with linear decay for nonlinear systems

    , Article IEEE Control Systems Letters ; Volume 6 , 2022 , Pages 313-318 ; 24751456 (ISSN) Shakouri, A ; Assadian, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Abstract
    In this letter, a new notion of stability is introduced, which is called triangular stability. A system is called triangularly stable if the norm of its state vector is bounded by a decreasing linear function of time such that its intersection point with the time axis can be arbitrarily commanded by the user. Triangular stability implies prescribed-time stability, which means that the nonlinear system is converged to zero equilibrium at an arbitrary finite time. A prescribed-time controller with guaranteed triangular stability is developed for normal form nonlinear systems with uncertain input gain, which is able to reject the disturbances and unmodeled dynamics. Numerical simulations are... 

    Control of Nonlinear Systems With Predefined Output Transient Performance

    , M.Sc. Thesis Sharif University of Technology Kamal Amiri, Ali (Author) ; Shahrokhi, Mohammad (Supervisor)
    Abstract
    This project is aimed to design a controller for nonlinear systems that satisfy a prescribed performance while guaranteeing close-loop stability. To do this, the controller must be designed in such a way that the transient response of the system has had these performance indices and does not exceed them. These performance indices predefine some constraints for systems’ output.A comprehensive form for the model system, the unknown dynamics of the system, consideration of a variety of constraints on the system input, usage of the time-finite method for the residence time and consideration of just one tuning parameter to reduce the computation load, are among the other benefits for the proposed... 

    Fibre position effects on the operation of opto-pair fibre displacement sensors

    , Article Optics and Laser Technology ; Volume 43, Issue 4 , 2011 , Pages 814-819 ; 00303992 (ISSN) Jafari, R ; Golnabi, H ; Sharif University of Technology
    Abstract
    In this article, two optical-fibre probes used in displacement measurements are reported. In one arrangement, two optical fibres with protective buffer jackets are placed together, while in the second arrangement, the protective buffer jackets are removed and the two fibres are placed with the claddings in contact, with a concomitant smaller centrecentre distance. As the core and cladding diameters are the same in both probes, the effect of the centrecentre distance on double-fibre designs can be investigated. The reflected output powers are recorded for the probes as a function of the axial distance from a reflective surface. A theoretical model is also implemented, which considers the... 

    Global Finite Time Stabilization of a Class of Uncertain MIMO Nonlinear Systems

    , Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 138, Issue 2 , 2016 ; 00220434 (ISSN) Abooee, A ; Moravej Khorasani, M ; Haeri, M ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME) 
    Abstract
    It is aimed to obtain global finite time stabilization of a class of uncertain multi-input-multi-output (MIMO) nonlinear systems in the presence of bounded disturbances by applying nonsingular terminal sliding mode controllers. The considered nonlinear systems consist of double integrator subsystems which interact with each other. In the proposed methods, new terminal sliding surfaces are introduced along with design of proper control inputs. The terminal sliding surfaces are defined such that the global finite time stability of sliding mode dynamic is attained. The control inputs are designed to steer the states into sliding motion within finite time and retain them on the terminal sliding... 

    Finite time-Lyapunov based approach for robust adaptive control of wind-induced oscillations in power transmission lines

    , Article Journal of Sound and Vibration ; Volume 371 , 2016 , Pages 19-34 ; 0022460X (ISSN) Ghabraei, S ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
    Academic Press  2016
    Abstract
    Large amplitude oscillation of the power transmission lines, which is also known as galloping phenomenon, has hazardous consequences such as short circuiting and failure of transmission line. In this article, to suppress the undesirable vibrations of the transmission lines, first the governing equations of transmission line are derived via mode summation technique. Then, due to the occurrence of large amplitude vibrations, nonlinear quadratic and cubic terms are included in the derived linear equations. To suppress the vibrations, arbitrary number of the piezoelectric actuators is assumed to exert the actuation forces. Afterwards, a Lyapunov based approach is proposed for the robust adaptive... 

    Optimization of CuIn1-XGaXS2 Nanoparticles and Their Application in the Hole-Transporting Layer of Highly Efficient and Stable Mixed-Halide Perovskite Solar Cells

    , Article ACS Applied Materials and Interfaces ; Volume 11, Issue 34 , 2019 , Pages 30838-30845 ; 19448244 (ISSN) Khorasani, A ; Marandi, M ; Khosroshahi, R ; Malekshahi Byranvand, M ; Dehghani, M ; Zad, A. I ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
    American Chemical Society  2019
    Abstract
    Inorganic hole-transport materials (HTMs) have been frequently applied in perovskite solar cells (PSCs) and are a promising solution to improve the poor stability of PSCs. In this study, we investigate solution-processed copper indium gallium disulfide (CIGS) nanocrystals (NCs) as a dopant-free inorganic HTM in n-i-p type PSCs. Moreover, Cs0.05(MA0.17-FA0.83)0.95Pb(I0.83Br0.17)3 mixed-halide perovskite with proper crystalline quality and long-time stability was utilized as the light-absorbing layer under ambient conditions. To optimize the cell performance and better charge extraction from the perovskite layer, the Ga concentration in the Cu(In1-XGaX)S2 composition was changed, and the X... 

    Sb2S3 and Cu3SbS4 nanocrystals as inorganic hole transporting materials in perovskite solar cells

    , Article Solar Energy ; Volume 223 , 2021 , Pages 106-112 ; 0038092X (ISSN) Mohamadkhani, F ; Heidariramsheh, M ; Javadpour, S ; Ghavaminia, E ; Mahdavi, S. M ; Taghavinia, N ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    One of the key parts of perovskite solar cells which has great influence on their performance and stability is hole transporting layer. Spiro-OMeTAD is extensively used as organic hole transporting material in perovskite solar cells. However, Spiro-OMeTAD is expensive and has low chemical stability. In this study, the solution processed Sb2S3 and Cu3SbS4 nanocrystals have been synthesized and then the n-i-p mesoscopic perovskite solar cells have been fabricated using Spiro-OMeTAD, Sb2S3 and Cu3SbS4 nanocrystals as hole transporting layer at ambient air condition. It is shown that the conduction and valence band levels of the synthesized Sb2S3 and Cu3SbS4 nanocrystals are in the proper... 

    Stable Photodetectors based on fstable photodetectors based on formamidinium lead iodide quantum well perovskite nanoparticles fabricated with excess organic cations.ormamidinium lead iodide quantum well perovskite nanoparticles fabricated with excess organic cations

    , Article ACS Applied Nano Materials ; Volume 4, Issue 8 , 2021 , Pages 7788-7799 ; 25740970 (ISSN) Hasanzadeh Azar, M ; Mohammadi, M ; Rezaei, N.T ; Aynehband, S ; Shooshtari, L ; Mohammadpour, R ; Simchi, A ; Sharif University of Technology
    American Chemical Society  2021
    Abstract
    Metal halide perovskite nanoparticles have recently attracted immense interest for photodetectors due to their outstanding optical and electronic properties such as high carrier diffusion length, tunable band gap (light absorption range), and high photoluminescence (PL) efficiency. Although significant progress has been achieved in the development of perovskites, their stability is yet to be addressed. To improve the stability and quantum efficiency of FAPbI3 perovskite nanocrystals, we present a room temperature protocol to fabricate fully passivated and stable FAPbI3 nanocrystals via 2D growth in the presence of amine ligands and an excess amount of the organic cations. The crystallization... 

    Simultaneous voltammetric determination of ascorbic acid, acetaminophen and isoniazid using thionine immobilized multi-walled carbon nanotube modified carbon paste electrode

    , Article Electrochimica Acta ; Volume 55, Issue 3 , 2010 , Pages 666-672 ; 00134686 (ISSN) Shahrokhian, S ; Asadian, E ; Sharif University of Technology
    2010
    Abstract
    A carbon paste electrode (CPE) modified with thionine immobilized on multi-walled carbon nanotube (MWCNT), was prepared for simultaneous determination of ascorbic acid (AA) and acetaminophen (AC) in the presence of isoniazid (INZ). The electrochemical response characteristics of the modified electrode toward AA, AC and INZ were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results showed an efficient catalytic role for the electro-oxidation of AA and AC, leading to a remarkable peak resolution (∼303 mV) for two compounds. On the other hand, the presence of INZ, which is considered as important drug interference for AC, does not affect the voltammetric responses... 

    Rapid and efficient synthesis of colloidal gold nanoparticles by arc discharge method

    , Article Applied Physics A: Materials Science and Processing ; Volume 96, Issue 2 , 2009 , Pages 423-428 ; 09478396 (ISSN) Ashkarran, A. A ; Iraji zad, A ; Mahdavi, M ; Ahadian, M. M ; Hormozi nezhad, M. R ; Sharif University of Technology
    2009
    Abstract
    We report a simple, inexpensive and one-step synthesis route of colloidal gold nanoparticles using arc discharge between titanium electrodes in HAuCl 4 solution achieving long-time stability. Gold nanoparticles of 8 nm diameter were formed during reduction of HAuCl4 in the plasma discharge zone. The resulting nanoparticles were characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Optical absorption spectroscopy of as prepared samples at 15 A arc current in HAuCl4 solution shows a surface plasmon resonance around 550 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal...