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Control of Nonlinear Systems With Predefined Output Transient Performance
, M.Sc. Thesis Sharif University of Technology ; 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...
Qualitative and Topological Properties of Some Partial Differential Equations
, M.Sc. Thesis Sharif University of Technology ; Hesaaraki, Mahmoud (Supervisor)
Abstract
This thesis is devoted to prove the existance of solution and structure of solu tion for some partial differential equations by using some modern topological and variational thechniques. Taking direction from the literature, this thesis is interested in existence, uniqueness, blow-up in finite time for some evolution equations, multiplicity and radial solution for certain elliptic partial differential equations.-Employing Fibrering, Galerkins, Mountain Pass-Lemma and lions com pactness Lemma are sharp in this thesis to prove the exsistence and multiplicity of solutions and overcome lack of compactness in some cases
The control of a thermal system with large time delay using of LQG and lead-compensator
, Article 2010 IEEE International Conference on Mechatronics and Automation, ICMA 2010, 4 August 2010 through 7 August 2010 ; August , 2010 , Pages 1842-1847 ; 9781424451418 (ISBN) ; Jahromi, A. F ; Abbasi, M ; Khayyat, A. A ; Sharif University of Technology
2010
Abstract
This paper will first describe the Linear-Quadratic-Gaussian (LQG) and Lead-Compensator when the Proportional-Integral-Derivative (PID) controllers are inactive for procedures that have large delay time (LDT) in transfer stage. Therefore in those states, LQG and Lead Compensator perform better than the PID controllers. The constrained LQG is optimal and stabilizing. The solution algorithm is guaranteed to terminate in finite time with a computational cost that has a reasonable upper bound compared to the minimal cost for computing the optimal solution. In this work all actual working area condition for instance noises and disturbances are considered. Eventually, LQG and Lead Compensator have...
Concurrent learning based finite time parameter estimation in adaptive control of uncertain switched systems
, Article 4th RSI International Conference on Robotics and Mechatronics, ICRoM 2016, 26 October 2016 through 28 October 2016 ; 2017 , Pages 258-265 ; 9781509032228 (ISBN) ; Nazari, S ; Sinafar, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper, We propose concurrent learning adaptive controller, which uses recorded and current data concurrently for adaptation, to model reference adaptive control (MRAC) of uncertain switched systems. In standard MRAC architecture for switched systems, the adaptive update laws are derived based on the gradient descent scheme, but here we developed two novel parameter estimation schemes by using modification terms in adaptation laws in which recorded data is used simultaneously with current data and a triggering time is considered in which a sufficient condition on the linear independence of the recorded data is obtained to guarantee the exponential convergence of tracking error and...
On the prescribed-time attractivity and frozen-time eigenvalues of linear time-varying systems
, Article Automatica ; Volume 140 , 2022 ; 00051098 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
A system is called prescribed-time attractive if its solution converges at an arbitrary user-defined finite time. In this note, necessary and sufficient conditions are developed for the prescribed-time attractivity of linear time-varying (LTV) systems. It is proved that the frozen-time eigenvalues of a prescribed-time attractive LTV system have negative real parts when the time is sufficiently close to the convergence moment. This result shows that the ubiquitous singularity problem of prescribed-time attractive LTV systems can be avoided without instability effects by switching to the corresponding frozen-time system at an appropriate time. Consequently, it is proved that the time-varying...
Finite-time consensus in directed switching network topologies and time-delayed communications
, Article Scientia Iranica ; Volume 18, Issue 1 B , February , 2011 , Pages 21-34 ; 10263098 (ISSN) ; Doostmohammadian, M. R ; Sharif University of Technology
2011
Abstract
There are many practical situations where it is desirable or even required to achieve stable convergence in the finite-time domain. In this paper, a simple distributed continuous-time protocol is introduced that guarantees finite-time consensus in networks of autonomous agents. Protocol convergence in weighted directed/undirected and fixed/switching networks is explored based on a Lyapunov analysis. The stability of the system and the solvability of the consensus algorithm are proved for network topologies that contain a spanning tree frequently enough over contiguous time intervals. The decision value for different topologies and for multi-rate integrator agents is investigated, and a novel...
Comment on S. Ahmed, H. Wang, and Y. Tian, “Robust adaptive fractional-order terminal sliding mode control for lower-limb exoskeleton,” Asian J. Control, vol. 21, no. 1, pp. 1–10 (2019)
, Article Asian Journal of Control ; 2022 ; 15618625 (ISSN) ; Sheikh Ahmadi, S ; Naderi Soorki, M ; Amini, S. S ; Sharif University of Technology
John Wiley and Sons Inc
2022
Abstract
In this comment, it is shown that there are some non-negligible big mistakes in the analyses and stability proof of the proposed controller in the quoted paper, which makes the main results of this paper to be incorrect. The main unavoidable mistakes in the stability analysis of the main theorem (Theorem 1) are stated and some remarks are also mentioned to fix some of them. © 2022 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd
Concurrent learning based finite-time parameter estimation in adaptive control of uncertain switched nonlinear systems
, Article Journal of Control, Automation and Electrical Systems ; Volume 28, Issue 4 , 2017 , Pages 444-456 ; 21953880 (ISSN) ; Yazdani, M ; Sinafar, B ; Sharif University of Technology
Springer New York LLC
2017
Abstract
In this paper, We develop concurrent learning adaptive controller, which uses recorded and current data concurrently for adaptation, to model reference adaptive control (MRAC) of uncertain switched nonlinear systems. In standard MRAC architecture for switched systems, the adaptive update laws are derived based on the gradient descent scheme, but here we developed two novel parameter estimation schemes by using modification terms in adaptation laws in which recorded data are used simultaneously with current data and a triggering time is considered in which a sufficient condition on the linear independence of the recorded data is obtained to guarantee the exponential convergence of tracking...
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) ; 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...
Adaptive finite-time fault-tolerant controller for a class of uncertain MIMO nonlinear switched systems subject to output constraints and unknown input nonlinearities
, Article Nonlinear Analysis: Hybrid Systems ; Volume 35 , February , 2020 ; Malek, S. A ; Shahrokhi, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this work, design of an adaptive finite-time fault-tolerant controller for a class of uncertain multi-input multi-output (MIMO) nonlinear switched systems with unmodeled dynamics subject to asymmetric time-varying output constraints and unknown faulty input nonlinearities has been addressed. The number of actuator faults can be infinite. In addition, the proposed control algorithm can cope with different unknown types of input nonlinearities namely, saturation, dead zone, backlash, and hysteresis. Actuator faults and input nonlinearities can be different in different modes. To estimate the system uncertainties, neural networks (NNs) have been employed and the unmodeled dynamics has been...
On the thermal efficiency of power cycles in finite time thermodynamics
, Article European Journal of Physics ; Volume 37, Issue 5 , 2016 ; 01430807 (ISSN) ; Morad, M. R ; Mahmoudi, A ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
The Carnot, Diesel, Otto, and Brayton power cycles are reconsidered endoreversibly in finite time thermodynamics (FTT). In particular, the thermal efficiency of these standard power cycles is compared to the well-known results in classical thermodynamics. The present analysis based on FTT modelling shows that a reduction in both the maximum and minimum temperatures of the cycle causes the thermal efficiency to increase. This is antithetical to the existing trend in the classical references. Under the assumption of endoreversibility, the relation between the efficiencies is also changed to ηCarnot > ηBrayton > ηDiesel > ηOtto, which is again very different from the corresponding classical...
Full quaternion based finite-time cascade attitude control approach via pulse modulation synthesis for a spacecraft
, Article ISA Transactions ; Volume 58 , 2015 , Pages 567-585 ; 00190578 (ISSN) ; Pasand, M ; Soltani, B ; Sharif University of Technology
ISA - Instrumentation, Systems, and Automation Society
2015
Abstract
In the aspect of further development of investigations in the area of spacecraft modeling and analysis of the control scheme, a new hybrid finite-time robust three-axis cascade attitude control approach is proposed via pulse modulation synthesis. The full quaternion based control approach proposed here is organized in association with both the inner and the outer closed loops. It is shown that the inner closed loop, which consists of the sliding mode finite-time control approach, the pulse width pulse frequency modulator, the control allocation and finally the dynamics of the spacecraft is realized to track the three-axis referenced commands of the angular velocities. The pulse width pulse...
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
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...
Closed-loop powered-coast-powered predictive guidance for spacecraft rendezvous with non-singular terminal sliding mode steering
, Article Acta Astronautica ; Volume 166 , 2020 , Pages 507-523 ; Ebrahimi, M ; Assadian, N ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The present study aims to present a guidance algorithm based on the relative motion prediction for orbital rendezvous, in which a coast phase is allowed between two powered phases. In both powered phases, the solution of the Hill-Clohessy-Wiltshire equations is used to find the required state variables at each time instant. To track the required trajectory and compensate for any orbital perturbations and uncertainties, a non-singular terminal sliding mode method is utilized as the steering law. Then, the finite time convergence of the state variables is mathematically proved. In addition, the starting time of the second powered phase is adapted to perturbations and uncertainties by another...
Design of a continuous fractional-order nonsingular terminal sliding mode control with time delay estimation for fes control of human knee joint
, Article 7th International Conference on Control, Instrumentation and Automation, ICCIA 2021, 23 February 2021 through 24 February 2021 ; 2021 ; 9780738124056 (ISBN) ; Abbasi, M ; Vossoughi, G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
The design of a novel Continuous Fractional-Order Nonsingular Terminal Sliding Mode controller is the focus of this study. Time Delay Estimation technique is incorporated into the controller. The proposed method is responsible for controlling the human knee joint neuromusculoskeletal model via Functional Electrical Stimulation. A second-order nonlinear model with time-varying coefficients is used for characterizing the FES-stimulated neuromusculoskeletal model. The presence of time-varying coefficients often complicates precise control of knee joint through FES and impairs the performance of conventional methods. To this end, the TDECFONTSM has been proposed consisting of three components, a...
Adaptive finite-time neural control of non-strict feedback systems subject to output constraint, unknown control direction, and input nonlinearities
, Article Information Sciences ; Volume 520 , 2020 , Pages 271-291 ; Shahrokhi, M ; Mohit, M ; Sharif University of Technology
Elsevier Inc
2020
Abstract
This paper addresses the finite-time controller design for a class of nonlinear systems in the non-strict feedback form subject to unknown system dynamics and disturbances, arbitrary asymmetric time-varying output constraints, four types of input nonlinearities, and unknown control direction. Utilizing the barrier Lyapunov function (BLF) and backstepping technique, an adaptive finite-time controller has been proposed. The difficulties associating with non-strict feedback systems have been handled using the variable separation approach. Furthermore, the unknown control direction problem has been tackled by using the Nussbaum gain function. A unified framework has been utilized for handling...
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) ; 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....
Developing a partial backlogging deteriorating inventory model with selling price dependant demand rate and cycle length dependant selling price
, Article 2008 IEEE International Conference on Industrial Engineering and Engineering Management, IEEM 2008, Singapore, 8 December 2008 through 11 December 2008 ; January , 2008 , Pages 198-202 ; 9781424426300 (ISBN) ; Sabahno, H ; Haji, R ; Sharif University of Technology
2008
Abstract
In this paper, we develop an inventory model with price dependant demand rate, under time value of money and inflation, finite time horizon, exponential backlogging rate and exponential deterioration rate with the objective of maximizing the present worth of the total system profit. Using a dynamic programming based solution algorithm, we are able to find the optimal sequence of the cycles and also to obtain different optimal selling prices and optimal order quantities for the cycles with unequal lengths, which have never been done before for our model. We also use a proper numerical example to show accuracy of the solution procedure. © 2008 IEEE
Developing two deteriorating inventory models with selling price dependant demand rate and cycle time dependant selling price
, Article 37th International Conference on Computers and Industrial Engineering 2007, Alexandria, 20 October 2007 through 23 October 2007 ; Volume 2 , 2007 , Pages 1330-1339 ; 9781627486811 (ISBN) ; Haji, R ; Sabahno, H ; Sharif University of Technology
2007
Abstract
In this paper we develop two models; the without shortages and the completely backlogging shortages with the price dependant demand rate under time value of money and inflation, finite time horizon and exponentially deterioration rate with the objective of maximizing the present worth of the total system profit. Using the dynamic programming method for each model, we are able to obtain different selling price, order quantity and cycle length for each cycle. We also use a proper numerical example to show accuracy of the solution procedures and to compare the results. This research and its results are unique and have never been concluded before
Finite-time stabilisation of a class of time-varying nonlinear systems by a mixed event-based and continuous-time strategy
, Article International Journal of Systems Science ; Volume 53, Issue 3 , 2022 , Pages 526-537 ; 00207721 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
In this paper, a mixed event-triggered and continuous-time control method is proposed, which can guarantee finite-time stabilisation of the fixed point in a class of time-varying nonlinear systems. Benefiting from an event-triggered framework, which is constructed based on the indefinite Lyapunov theory, the communication/computation costs in the transient time can be reduced by using the proposed method. In a special case, this method is converted to a fully event-triggered control strategy for asymptotic stabilisation of the fixed point in the considered class of time-varying nonlinear systems. The effectiveness of the proposed method is verified by numerical simulations. © 2021 Informa UK...