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Implementation and intelligent gain tuning feedback–based optimal torque control of a rotary parallel robot
, Article JVC/Journal of Vibration and Control ; Volume 28, Issue 19-20 , 2022 , Pages 2678-2695 ; 10775463 (ISSN) ; Ebrahimi Toulkani, N ; Sharif University of Technology
SAGE Publications Inc
2022
Abstract
Aiming at operating optimally minimizing error of tracking and designing control effort, this study presents a novel generalizable methodology of an optimal torque control for a 6-degree-of-freedom Stewart platform with rotary actuators. In the proposed approach, a linear quadratic integral regulator with the least sensitivity to controller parameter choices is designed, associated with an online artificial neural network gain tuning. The nonlinear system is implemented in ADAMS, and the controller is formulated in MATLAB to minimize the real-time tracking error robustly. To validate the controller performance, MATLAB and ADAMS are linked together and the performance of the controller on the...
Stabilizing periodic orbits of fractional order chaotic systems via linear feedback theory
, Article Applied Mathematical Modelling ; Vol. 36, Issue 3 , 2012 , pp. 863-877 ; ISSN: 0307904X ; Salarieh, H ; Alasty, A ; Sharif University of Technology
Abstract
In this paper stabilizing unstable periodic orbits (UPO) in a chaotic fractional order system is studied. Firstly, a technique for finding unstable periodic orbits in chaotic fractional order systems is stated. Then by applying this technique to the fractional van der Pol and fractional Duffing systems as two demonstrative examples, their unstable periodic orbits are found. After that, a method is presented for stabilization of the discovered UPOs based on the theories of stability of linear integer order and fractional order systems. Finally, based on the proposed idea a linear feedback controller is applied to the systems and simulations are done for demonstration of controller performance...
Design of a robust model predictive controller with reduced computational complexity
, Article ISA Transactions ; Volume 53, Issue 6 , 1 November , 2014 , Pages 1754-1759 ; ISSN: 00190578 ; Haeri, M ; Sharif University of Technology
Abstract
The practicality of robust model predictive control of systems with model uncertainties depends on the time consumed for solving a defined optimization problem. This paper presents a method for the computational complexity reduction in a robust model predictive control. First a scaled state vector is defined such that the objective function contours in the defined optimization problem become vertical or horizontal ellipses or circles, and then the control input is determined at each sampling time as a state feedback that minimizes the infinite horizon objective function by solving some linear matrix inequalities. The simulation results show that the number of iterations to solve the problem...
Stabilizing periodic orbits of fractional order chaotic systems via linear feedback theory
, Article Applied Mathematical Modelling ; Volume 36, Issue 3 , 2012 , Pages 863-877 ; 0307904X (ISSN) ; Salarieh, H ; Alasty, A ; Sharif University of Technology
Abstract
In this paper stabilizing unstable periodic orbits (UPO) in a chaotic fractional order system is studied. Firstly, a technique for finding unstable periodic orbits in chaotic fractional order systems is stated. Then by applying this technique to the fractional van der Pol and fractional Duffing systems as two demonstrative examples, their unstable periodic orbits are found. After that, a method is presented for stabilization of the discovered UPOs based on the theories of stability of linear integer order and fractional order systems. Finally, based on the proposed idea a linear feedback controller is applied to the systems and simulations are done for demonstration of controller performance...
Designing optimal controllers for nonlinear frames by considering the effect of response feedback
, Article Scientia Iranica ; Volume 18, Issue 6 , 2011 , Pages 1170-1178 ; 10263098 (ISSN) ; Mohebbi, M ; Sharif University of Technology
Abstract
The effect of response feedback on designing optimal controllers for nonlinear frames has been studied. Different combinations of response feedback have been used in the performance index. The Newmark based nonlinear instantaneous optimal control algorithm has been used as the control algorithm in controlling the response of an eight-story bilinear hysteretic frame subjected to white noise excitation and real earthquakes, and controlled by either eight actuators or a single actuator. While the objective has been to minimize the maximum control force for reducing the maximum drift to below the yielding level, the distributed genetic algorithm (DGA) has been used to determine the proper set of...
Adaptive control of robot manipulators including actuator dynamics and without joint torque measurement
, Article 2010 IEEE International Conference on Robotics and Automation, ICRA 2010, Anchorage, AK, 3 May 2010 through 7 May 2010 ; 2010 , Pages 4639-4644 ; 10504729 (ISSN) ; 9781424450381 (ISBN) ; Namvar, M ; Sharif University of Technology
2010
Abstract
Ignoring actuator dynamics in control of rigid manipulators can in practice result in performance degradation or loss of system stability. However, consideration of actuator dynamics usually requires measurement of robot joint torques. This paper addresses motion tracking control of an n-DOF rigid robot by taking into account its actuator dynamics. Joint torque measurement is avoided by using an adaptive observer. The backstepping technique is adopted to develop a dynamically smooth adaptive nonlinear controller dealing with uncertainties in manipulator and actuator dynamics. Semi-global convergence of motion tracking errors as well as torque estimation error are proven without any...
An investigation on the performance of receiving optical beam-forming networks
, Article Final Program and Book of Abstracts - iWAT 2010: 2010 International Workshop on Antenna Technology: Small Antennas, Innovative Structures and Materials, 1 March 2010 through 3 March 2010 ; March , 2010 ; 9781424448845 (ISBN) ; Akbari, M ; Sharif University of Technology
2010
Abstract
Next generation wideband and ultra-wideband radar antenna arrays need efficient true-time delay networks for array control. Following the great interest for optical control of antenna array beam steering, performance analysis of optical beam-formers is a must. In this paper signal to noise ratio and dynamic range of simple optical beamforming structures with components off the shelf are investigated theoretically. Especially the effects of certain power combining components such as arrayed wave guide gratings, broadband passive optical combiners and microwave combiners inspected. It turns up that an efficient microwave combiner would surpass the optical combiners in both SNR and dynamic...
Simulation and control of membrane reactors for catalytic reduction of dissolved oxygen from water
, Article Canadian Journal of Chemical Engineering ; 2017 ; 00084034 (ISSN) ; Golmakani, A ; Hosseinipoor, S ; Rokhforouz, M. R ; Sharif University of Technology
Wiley-Liss Inc
2017
Abstract
Removal of dissolved oxygen (DO) from water has gained much attention in recent decades to prevent different problems such as corrosion, bio-fouling, and performance degradation in many industries. The traditional physical and chemical methods for DO removal have found wide application in industries. However, physical methods have low efficiency and chemical methods often produce undesirable products. Therefore, catalytic reduction by hydrogen has been regarded by a variety of industries recently. In this study, catalytic reduction of DO from water is examined using membrane reactors. The mathematical model of this system is developed while considering the axial dispersion, membrane...
Multimodel control of nonlinear systems: An improved gap metric and stability margin-based method
, Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 140, Issue 8 , 2018 ; 00220434 (ISSN) ; Haeri, M ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2018
Abstract
This paper presents a new multimodel controller design approach incorporating stability and performance criteria. The gap metric is employed to measure the distance between local models. An efficient method based on state feedback strategy is introduced to improve the maximum stability margin of the local models. The proposed method avoids local model redundancy, simplifies the multimodel controller structure, and supports employing of many linear control techniques, while does not rely on a priori experience to choose the gridding threshold value. To evaluate the proposed method, three benchmark nonlinear systems are studied. Simulation results demonstrate that the method provides the...
Wind turbine power improvement utilizing passive flow control with microtab
, Article Energy ; Volume 150 , 2018 , Pages 575-582 ; 03605442 (ISSN) ; Movahhedi, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this study, the effect of deploying microtabs on performance improvement of a horizontal axis wind turbine blade is numerically investigated in three-dimensions. The NREL Phase VI, a stall-regulated upwind wind turbine, is used as the baseline case. Different cases are considered to investigate the effects of spanwise location as well as the height variation of tabs along the blade span, on the flow over the rotor blade. In all cases, the tab is located at 95% chord of the airfoil section on the lower surface of the blade. Results reveal that locating microtabs at the outboard part of the blade has a greater impact on the rotor performance than the inboard part. However, both cases...
Simulation and control of membrane reactors for catalytic reduction of dissolved oxygen from water
, Article Canadian Journal of Chemical Engineering ; Volume 96, Issue 4 , 2018 , Pages 912-925 ; 00084034 (ISSN) ; Golmakani, A ; Hosseinipoor, S ; Rokhforouz, M. R ; Sharif University of Technology
Wiley-Liss Inc
2018
Abstract
The catalytic reduction of dissolved oxygen (DO) from water was examined using membrane reactors and a mathematical model that considers axial dispersion, membrane permeation, and chemical reaction. The model is solved in steady state mode and the effect of various parameters on the DO removal was assessed. The results of steady state mode were employed as initial conditions for solving the model in dynamic mode. The impact of operating conditions, e.g., water flow rate, DO concentration of influent water, hydrogen flow rate, and hydrogen pressure on the performance of the DO process was studied. Results of the dynamic simulation suggested that hydrogen pressure is the best option to be used...
A multi-model control of nonlinear systems: a cascade decoupled design procedure based on stability and performance
, Article Transactions of the Institute of Measurement and Control ; Volume 42, Issue 7 , 2020 , Pages 1271-1280 ; Rikhtehgar, P ; Haeri, M ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
Recently, the multi-model controllers design was proposed in the literature based on integrating of the stability and performance criteria. Although these methods overcome the redundancy problem, the decomposition step is very complex and time consuming. In this paper, a cascade design of multi-model control is presented that is made from two sequential steps. In the first step, the nonlinear system is decomposed into a set of linear subsystems by just considering the stability criterion. In this step, the gap metric is used as a smart tool to measure the distance between linear subsystems. While the closed-loop stability is gained through the first step, the performance is improved in the...
A practical approach to networked control design for robust H∞ performance in the presence of uncertainties in both communication and system
, Article Applied Mathematics and Computation ; Volume 381 , 2020 ; Tavassoli, B ; Farhadi, A ; Sharif University of Technology
Elsevier Inc
2020
Abstract
This work presents results on the development of robust H∞ control strategy for Networked Control Systems (NCSs) by involving uncertainties in both communication and controlled plant subsystems. The network-induced delays in both communication links (to and from the controller) are assumed to behave as Markov chains. An analytical approach is presented to calculate the transition probabilities of the Markovian network-induced delays. By employing the augmentation method, the resultant system is converted into a delay-free uncertain singular Markovian jump system with bounded transition probabilities. New conditions are established to assure that the uncertain NCS satisfies an H∞ performance...
Coupling analysis and control of axial and torsional vibrations in a horizontal drill string
, Article Journal of Petroleum Science and Engineering ; Volume 195 , 2020 ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Vertical drilling methods have been often used for oil and gas extraction so far. In some places, for further extraction and access to the locations that cannot be obtained by the vertical drilling (due to its restrictions); horizontal drilling has become more popular. In horizontal drilling, a variety of longitudinal, torsional and lateral vibrations occur. These vibrations, if left uncontrolled, can damage the drilling rig and equipment, as well as reduce the efficiency of the drilling process and increase the processing time. The purpose of this research is to obtain the coupled axial and torsional vibration equations by analysing the vibrational modes in the horizontal section of the...
Application of fractional derivative in control functions
, Article Proceedings of the INDICON 2008 IEEE Conference and Exhibition on Control, Communications and Automation, 11 December 2008 through 13 December 2008, Kanpur ; Volume 1 , 2008 , Pages 252-257 ; 9781424427475 (ISBN) ; Haeri, M ; Sharif University of Technology
2008
Abstract
Application of fractional derivative in control problems such as sliding surface design in Sliding Mode Control, training of MLP in neural networks, and parameters updating in Model Reference Adaptive Control is studied in this paper. Use of the fractional derivative increases possibility of improving the control performance by reducing the convergence time in the mentioned control problems. This gain is attained due to the higher degree of freedom exist in the fractional dynamical systems. We study such control problems by replacing the integer order derivative with the fractional order derivative. The performance of the proposed methods is illustrated through computer simulations of gyro...
Modeling and Control of gas turbine combustor with dynamic and Adaptive Neural networks
, Article International Journal of Engineering, Transactions B: Applications ; Volume 21, Issue 1 , 2008 , Pages 71-84 ; 1728-144X (ISSN) ; Lahroodi, M ; Sharif University of Technology
Materials and Energy Research Center
2008
Abstract
This paper presents an Artificial Neural Network (ANN)-based modeling technique for prediction of outlet temperature, pressure and mass flow rate of gas turbine combustor. Results obtained by present modeling were compared with those obtained by experiment. The results showed the effectiveness and capability of the proposed modeling technique with reasonable accuracies of about 95 percent. This paper describes a nonlinear SVFAC (State Vector Feedback Adaptive Control) controller scheme for gas turbine combustor. In order to achieve the satisfied control performance, we have to consider the effect of nonlinear factors contained in controller. The controller is adaptively trained to force the...
Enhancement of the tipover stability of mobile manipulators with non-holonomic constraints using an adaptive neuro-fuzzy-based controller
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 223, Issue 2 , 2009 , Pages 201-213 ; 09596518 (ISSN) ; Meghdari, A ; Naderi, D ; Eslami, S ; Sharif University of Technology
2009
Abstract
The stability issue of mobile manipulators, particularly when the end-effector and the vehicle have to follow a predefined trajectory (for some special duties like painting a plane or carrying a light load), is a crucial subject and needs special attention. In this paper, by utilizing the manipulator compensation motions, the instantaneous proper configuration for a redundant mobile robot is determined. A fast methodology taking into account the dynamic interaction between the manipulator and the vehicle is proposed for enhancing the tipover stability (i.e. stability against overturning) of the mobile manipulator by employing the soft computing approach including a genetic algorithm, neural...
Coordinated control of doubley fed induction generator virtual inertia and power system oscillation damping using fuzzy logic
, Article International Journal of Engineering, Transactions A: Basics ; Volume 32, Issue 4 , 2019 , Pages 536-547 ; 17281431 (ISSN) ; Ranjbar, A. M ; Mozafari, B ; Sharif University of Technology
Materials and Energy Research Center
2019
Abstract
Doubly-fed induction generator (DFIG) based wind turbines with traditional maximum power point tracking (MPPT) control provide no inertia response under system frequency events. Recently, the DFIG wind turbines have been equipped with virtual inertia controller (VIC) for supporting power system frequency stability. However, the conventional VICs with fixed gain have negative effects on inter-area oscillations of regional networks. To cope with this drawback, this paper proposes a novel adaptive VIC to improve both the inter-area oscillations and frequency stability. In the proposed scheme, the gain of VIC is dynamically adjusted using fuzzy logic. The effectiveness and control performance of...