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closed-loop-control-systems
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Achieving transparency in series elastic actuator of sharif lower limb exoskeleton using LLNF-NARX model
, Article 4th RSI International Conference on Robotics and Mechatronics, ICRoM 2016, 26 October 2016 through 28 October 2016 ; 2017 , Pages 398-403 ; 9781509032228 (ISBN) ; Ghaffari, S ; Vossoughi, G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Nowadays, exoskeletons have been gaining popularity due to their potential use in rehabilitation and augmentation. These robots often utilize series elastic actuators to facilitate compliant interaction with the human. Numerous studies have been carried out with the purpose of identification and control of these type of actuators. The goal of this paper is to provide a method for dynamic modeling and identification of series elastic actuators. This model is then used in the control loop as a feed-forward term to eliminate the actuator's dynamics. Each series elastic actuator used in the Sharif wearable robot, uses a brushless DC motor, a torsional spring, a harmonic drive, a timing belt, a...
An Extremely low ripple high voltage power supply for pulsed current applications
, Article IEEE Transactions on Power Electronics ; Volume 35, Issue 8 , 2020 , Pages 7991-8001 ; Mohsenzade, S ; Hadizade, A ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This article describes the development of an 18 kV, 30 kW power supply for a pulsed current load with the maximum current of 20 A and a di/dt equal to 100 A/μs. The achieved output ripple is less than 0.01%. In such a high level of precision, the most important issues are considerable difference between the instantaneous and average output powers, as well as insufficient reaction speed of the converter to the fast load change. Very low level of the voltage feedback and its sensitivity to the noise. The first issue necessitates a notable overdesign of the converter switches if the output voltage precision is dedicated to the converter. The second issue raises the problems relevant to...
DC-link loop bandwidth selection strategy for grid-connected inverters considering power quality requirements
, Article International Journal of Electrical Power and Energy Systems ; Volume 119 , 2020 ; Mokhtari, H ; Ghasemi, M. A ; Peyghami, S ; Davari, P ; Blaabjerg, F ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
DC-link voltage and output current control loops are two cascaded loops in the control structure of grid-connected inverters. A high DC-link voltage loop bandwidth (DCL-BW) provides more disturbance rejection capability for the control loop and is preferred from control system perspective. However, for stability issues, this BW is limited and must be sufficiently less than that of the current control loop. Among the different control schemes, instantaneous active reactive control (IARC) method provides the highest possible DCL-BW (i.e., 0.02 × switching frequency). Having this degree of freedom in the controller design, a proper methodology should be defined for selection of DCL-BW. In this...
Winding function model for predicting performance of 2-DOF wound rotor resolver
, Article IEEE Transactions on Transportation Electrification ; Volume 8, Issue 2 , 2022 , Pages 2062-2069 ; 23327782 (ISSN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Two-degree-of-freedom (2-DOF) electrical machines require position sensors for their motion control. In comparison with using two independent sensors, using a 2-DOF sensor enhances the closed-loop control system's performance. However, due to the 3-D structure of the 2-DOF sensor, its performance evaluation needs 3-D analysis. Also, due to helical motion the accuracy deterioration of the sensor, under mechanical faults needs more attention. Although the finite element method (FEM) is the best way to simulate such sensors, most of the commercial packages for transient finite element simulations are not able to consider two separate motions simultaneously. Furthermore, FEM has a high...
Robust adaptive fractional order proportional integral derivative controller design for uncertain fractional order nonlinear systems using sliding mode control
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 232, Issue 5 , 1 May , 2018 , Pages 550-557 ; 09596518 (ISSN) ; Salarieh, H ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
This article presents a robust adaptive fractional order proportional integral derivative controller for a class of uncertain fractional order nonlinear systems using fractional order sliding mode control. The goal is to achieve closed-loop control system robustness against the system uncertainty and external disturbance. The fractional order proportional integral derivative controller gains are adjustable and will be updated using the gradient method from a proper sliding surface. A supervisory controller is used to guarantee the stability of the closed-loop fractional order proportional integral derivative control system. Finally, fractional order Duffing–Holmes system is used to verify...
Adaptive synchronization of uncertain fractional-order chaotic systems using sliding mode control techniques
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 234, Issue 1 , 2020 , Pages 3-9 ; Siahi Shadbad, A ; Safavi, K ; Salarieh, H ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
In this article, an adaptive nonlinear controller is designed to synchronize two uncertain fractional-order chaotic systems using fractional-order sliding mode control. The controller structure and adaptation laws are chosen such that asymptotic stability of the closed-loop control system is guaranteed. The adaptation laws are being calculated from a proper sliding surface using the Lyapunov stability theory. This method guarantees the closed-loop control system robustness against the system uncertainties and external disturbances. Eventually, the presented method is used to synchronize two fractional-order gyro and Duffing systems, and the numerical simulation results demonstrate the...
Design of an stable GPC for nonminimum phase LTI systems
, Article Wec 05: Fourth World Enformatika Conference, Istanbul, 24 June 2005 through 26 June 2005 ; Volume 6 , 2005 , Pages 88-91 ; 9759845857 (ISBN); 9789759845858 (ISBN) ; Haeri, M ; Sharif University of Technology
2005
Abstract
The current methods of predictive controllers are utilized for those processes in which the rate of output variations is not high. For such processes, therefore, stability can be achieved by implementing the constrained predictive controller or applying infinite prediction horizon. When the rate of the output growth is high (e.g. for unstable nonminimum phase process) the stabilization seems to be problematic. In order to avoid this, it is suggested to change the method in the way that: first, the prediction error growth should be decreased at the early stage of the prediction horizon, and second, the rate of the error variation should be penalized. The growth of the error is decreased...
Design of fractional order proportional-integral-derivative controller based on moment matching and characteristic ratio assignment method
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 225, Issue 8 , December , 2011 , Pages 1040-1053 ; 09596518 (ISSN) ; Haeri, M ; Sharif University of Technology
2011
Abstract
This paper presents a new analytical method to design fractional-order proportional- integral-derivative (PID) controllers. The control parameters are calculated so that the closedloop system approximates a desired transfer function with transient response requirements. This function is determined based on the characteristic ratio assignment method. The control parameters are calculated by matching the first three moments of the closed-loop transfer function with the corresponding values of the desired system. Furthermore, to ensure closed-loop stability the proposed method is improved by using the shifted moments around the crossover frequency. Illustrative examples are given to show the...
Control of a nonlinear system using the saturation phenomenon
, Article Nonlinear Dynamics ; Volume 42, Issue 2 , 2005 , Pages 113-136 ; 0924090X (ISSN) ; Ghorashi, M ; Sharif University of Technology
2005
Abstract
In this paper, a theoretical investigation of nonlinear vibrations of a 2 degrees of freedom system when subjected to saturation is studied. The method has been especially applied to a system that consists of a DC motor with a nonlinear controller and a harmonic forcing voltage. Approximate solutions are sought using the method of multiple scales. It is shown that the closed-loop system exhibits different response regimes. The nature and stability of these regimes are studied and the stability boundaries are obtained. The effects of the initial conditions on the response of the system have also been investigated. Furthermore, the second-order solution is presented and the corresponding...
Robust distributed control of spacecraft formation flying with adaptive network topology
, Article Acta Astronautica ; Volume 136 , 2017 , Pages 281-296 ; 00945765 (ISSN) ; Alasty, A ; Assadian, N ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In this study, the distributed six degree-of-freedom (6-DOF) coordinated control of spacecraft formation flying in low earth orbit (LEO) has been investigated. For this purpose, an accurate coupled translational and attitude relative dynamics model of the spacecraft with respect to the reference orbit (virtual leader) is presented by considering the most effective perturbation acceleration forces on LEO satellites, i.e. the second zonal harmonic and the atmospheric drag. Subsequently, the 6-DOF coordinated control of spacecraft in formation is studied. During the mission, the spacecraft communicate with each other through a switching network topology in which the weights of its graph...
Adaptive fuzzy backstepping approach for temperature control of continuous stirred tank reactors
, Article Fuzzy Sets and Systems ; Volume 160, Issue 12 , 2009 , Pages 1804-1818 ; 01650114 (ISSN) ; Shahrokhi, M ; Sharif University of Technology
2009
Abstract
In this paper, an adaptive fuzzy controller, based on backstepping technique, has been proposed for temperature control of a general class of continuous stirred tank reactors (CSTRs). Using the observability concept, an adaptive fuzzy controller using temperature measurement has been designed. A fuzzy logic system is used to estimate the concentration dependent terms and other unknown system parameters appearing in the control law. It is shown that the closed loop system is asymptotically stable and influences of minimum approximation error and external disturbance on the L2 norm of the output tracking error can be attenuated arbitrarily. The performance of the proposed controller has been...
Application of neural networks to decentralized control of robot manipulators with high degree of freedom
, Article ICTAI 2005: 17th IEEE International Conference on Tools with Artificial Intelligence, ICTAI'05, Hong Kong, 14 November 2005 through 16 November 2005 ; Volume 2005 , 2005 , Pages 484-488 ; 10823409 (ISSN); 0769524885 (ISBN); 9780769524887 (ISBN) ; Elhamifar, E ; Sharif University of Technology
2005
Abstract
In this paper a neural network decentralized control for trajectory tracking of robot manipulators is developed. The proposed decentralized control allows the overall closed-loop system to be stabilized while making the tracking error to be uniformly ultimately bounded (UUB), without having any prior knowledge of the robot manipulator dynamics. The interconnections in the dynamic equations of each subsystem are considered with unknown nonlinear bounds. The RBF neural networks (RBFNNs) are proposed to model the unknown nonlinear dynamics of the robots and the interconnection terms. Using Lyapunov method, the stability of the overall system is investigated, © 2005 IEEE
Output feedback adaptive decentralized control of cooperative robots
, Article ICIECA 2005: International Conference on Industrial Electronics and Control Applications 2005, Quito, 29 November 2005 through 2 December 2005 ; Volume 2005 , 2005 ; 0780394194 (ISBN); 9780780394193 (ISBN) ; Elhamifar, E ; Sharif University of Technology
IEEE Computer Society
2005
Abstract
In this paper a decentralized control scheme for multiple cooperative manipulators is developed to achieve the desired performance in motion and force tracking, in the presence of uncertainties in dynamic equations of the robots. To eliminate the effects of uncertainties in the closed-loop performance, a new adaptive control algorithm is proposed. Based on the Lyapunov stability method, it is proved that all the error signals in the closed-loop system which is compose of a robot, an observer and a controller asymptotically converge to zero. Also to avoid the difficulties of using velocity sensors within the cooperative system, an output feedback control scheme with a linear observer is used....
Position control of ionic polymer-metal composites using fuzzy logic
, Article 2008 ASME International Mechanical Engineering Congress and Exposition, IMECE 2008, Boston, MA, 31 October 2008 through 6 November 2008 ; Volume 11 , 2009 , Pages 575-581 ; 9780791848722 (ISBN) ; Honarvar, M ; Alasty, A ; Meghdari, A ; Zohor, H ; Sharif University of Technology
2009
Abstract
The Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers which generate large deformation under a low driving voltage. In this paper an empirical model of IPMC is developed by measuring the step response of a 23 mmx3.6 mmx0.16 mm IPMC strip in a cantilever configuration. Moreover, a model-based precision position control of an IPMC base on the fuzzy logic is presented. Open-loop position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeatability and reliability. A CCD camera was used to observe the closed loop response of the IPMC strip in order to control this...
Non-linear feedback optimal control law for minimum-time injection problem using fuzzy system
, Article Aircraft Engineering and Aerospace Technology ; Volume 77, Issue 5 , 2005 , Pages 376-383 ; 00022667 (ISSN) ; Rahbar, N ; Novinzadeh, A. B ; Sharif University of Technology
2005
Abstract
Purpose - To devise a new technique to synthesise optimal feedback control law for non-linear dynamic systems through fuzzy logic. Design/methodology/approach - The proposed methodology utilizes the open-loop optimal control solutions (OCSs) of the non-linear systems for the training of the fuzzy system in the process of developing closed-loop fuzzy logic guidance (FLG). This is achieved through defining a set of non-dimensionalised variables related to the system states. Findings - FLG is capable of generating closed-loop control law for the non-linear problem investigated. Since the proposed fuzzy structure is independent of the system equations, the approach is potentially applicable to...
A novel method on singularity analysis in parallel manipulators
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Mahnama, M ; Zohoor, H ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
A parallel manipulator is a closed loop mechanism in which a moving platform is connected to the base by at least two serial kinematic chains. The main problem engaged in these mechanisms, is their restricted working space as a result of singularities. In order to tackle these problems, many methods have been introduced by scholars. However, most of the mentioned methods are too much time consuming and need a great amount of computations. They also in most cases do not provide a good insight to the existence of singularity for the designer. In this paper a novel approach is introduced and utilized to identify singularities in parallel manipulators. By applying the new method, one could get a...
Satellite attitude control using three reaction wheels
, Article 2008 American Control Conference, ACC, Seattle, WA, 11 June 2008 through 13 June 2008 ; 2008 , Pages 4850-4855 ; 07431619 (ISSN) ; 9781424420797 (ISBN) ; Farooq, U ; Alasty, A ; Issa, J ; Sharif University of Technology
2008
Abstract
This work addresses the attitude control of a satellite by applying MIMO quantitative feedback approach. The objective is to design a set of proper controllers in presence of unknown disturbances and parametric uncertainties for a nonlinear MIMO system. The physical model of satellite utilizes three reaction wheels as actuators. The controller goal is to change the rotational speed of reaction wheels to adjust the satellite in desired course. First, the mathematical model of satellite and its actuators using angular kinematics and kinetic equations is developed. Quantitative feedback theory is then applied to synthesize a set of linear controllers that deals with both nonlinearities in the...
A new method to control heat and mass transfer to work piece in a GMAW process
, Article Journal of Process Control ; Volume 22, Issue 6 , 2012 , Pages 1087-1102 ; 09591524 (ISSN) ; Haeri, M ; Sharif University of Technology
2012
Abstract
It is proposed to employ melting rate, heat input, and detaching droplet diameter as controlled variables to control heat and mass transfer to work piece in a gas metal arc welding process. A two-layer architecture with cascade configuration of PI and MPC controllers is implemented to incorporate existing constraints on the process variables, improve transient behavior of the closed-loop responses and reduce interaction level. Computer simulation results are presented to indicate usefulness of the proposed controlled variables selection and applying two-layer control architecture to control heat and mass transfer to work piece
Robust D-stability test of LTI general fractional order control systems
, Article IEEE/CAA Journal of Automatica Sinica ; Volume 7, Issue 3 , May , 2020 , Pages 853-864 ; Liu, X ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This work deals with the robust D-stability test of linear time-invariant ( LTI ) general fractional order control systems in a closed loop where the system and - or the controller may be of fractional order. The concept of general implies that the characteristic equation of the LTI closed loop control system may be of both commensurate and non-commensurate orders, both the coefficients and the orders of the characteristic equation may be nonlinear functions of uncertain parameters, and the coefficients may be complex numbers. Some new specific areas for the roots of the characteristic equation are found so that they reduce the computational burden of testing the robust D-stability. Based on...
Robust D-stabilization analysis of fractional-order control systems with complex and linearly dependent coefficients
, Article IEEE Transactions on Systems, Man, and Cybernetics: Systems ; 2020 ; Fathi Jegarkandi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This article focuses on the robust D-stabilization analysis of fractional-order control systems where each of the system and the controller may be of fractional order. The coefficients of the system are considered as complex linear functions of interval uncertain parameters, so this article deals with fractional-order polytopic systems. First, a necessary and sufficient condition is introduced for the robust D-stabilization of the closed-loop control system based on the zero exclusion condition and the value set concept. Then, the geometric pattern of the value set of the characteristic polynomial is obtained analytically using the exposed vertices. Second, a function is presented to check...