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IET Power Electronics (17554543) 18(1)
This paper presents a novel high-performance and dependable step-up multi-level inverter topology designed specifically for photovoltaic applications. A gain factor of nine is attained, coupled with automatic self-voltage balancing of capacitors and the intrinsic capability to generate both positive and negative voltage levels. All power switches withstand voltages lower than the peak of the output voltage. The quantity of power switches, DC input sources, and the blocking voltage on the switches are reduced. Also, the proposed inverter demonstrates a minimal cost function in comparison to similar topologies. The performance of the 19-level step-up inverter has been confirmed through simulation as well as laboratory results obtained from a constructed prototype. © 2025 The Author(s). IET Power Electronics published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
Chemical Engineering Communications (00986445) 212(8)pp. 1233-1242
In this article, a robust control algorithm is proposed for a nonlinear and time-varying continuous stirred tank reactor (CSTR) with sediment formation in the cooling jacket. The existing control schemes may fail, as deposition measurement or estimation is a challenge in such a process. As a main contribution, the deposition phenomenon is modeled here as the system uncertainty. Then, an identification-based robust integral controller is constructed for the underlying CSTR. Applying the loop-shaping procedure here is also a novelty to satisfy the performance objectives in the frequency domain. In a comprehensive scenario, which includes the set-point tracking in the presence of system uncertainties and external disturbance, the performance of the proposed robust control system is evaluated and discussed from a comparison viewpoint. The numerical study shows that fouling control and robust performance are ensured by the developed H∞-based technique. © 2025 Taylor & Francis Group, LLC.
International Journal of Systems Science (00207721) 56(8)pp. 1726-1741
Piezoelectric deformable mirrors are complex systems with a reflective face-sheet and underlying actuators. The inherent hysteresis phenomenon in piezoelectric materials introduces nonlinearity and delay, rendering conventional control methods inappropriate for deformable mirror actuation. This study presents a disturbance observer-based controller with the generalised Bouc–Wen hysteresis parameter identification algorithm. Analytical proofs establish fixed-time stability for the observer and controller. A key feature of the proposed disturbance observer is the convergence of the estimated hysteresis to the actual value after a prescribed settling time, which facilitates precise hysteresis parameter identification. This is based on a data clustering technique, unlike most previous works. The proposed controller has the capability of hysteresis compensation and reference tracking in the piezoelectric deformable mirror actuators. Numerical simulation results are present to evaluate the tracking performance of the controller in the presence of random wavefront, the convergence of disturbance to the actual value in the fixed time, and identification of hysteresis parameters. © 2024 Informa UK Limited, trading as Taylor & Francis Group.
International Journal of Systems Science (00207721) 56(8)pp. 1784-1800
This paper investigates incrementally input-to-state stability ((Formula presented.) ISS) for the interconnection of infinitely many finite-dimensional discrete-time switched subsystems (DtSS), using finite-step Lyapunov functions (FSLF). Unlike many previous investigations, each subsystem in the network may be not necessarily δISS, considering the potential effects of subsystems on each other. The proposed analysis method shows that the size of the truncation of an infinite network does not need to be known. As an application, assuming the subsystems only need to have M-step approximate bisimilarity relations, it is possible to construct approximately bisimilar abstractions, under small-gain type conditions. The effectiveness of the proposed technique is illustrated through an islanded microgrid, consisting of infinitely many subsystems. © 2024 Informa UK Limited, trading as Taylor & Francis Group.
ISA Transactions (00190578) 164pp. 1-13
Data-driven control methods in the frequency domain commonly require the determination of controller structure. Relaxing such restriction in the proposed algorithm, the controller design is transformed into an optimization problem, based on the υ-gap Metric criterion. By defining a desired stability margin and the desired frequency response of the controller, a criterion is determined to characterize a family of controllers. Therefore, a model free procedure is proposed to determine a family of controllers, by taking the plant frequency response and the desired stability margin. On the other hand, by adopting a new index, presented in this paper, the designer can determine the optimal controller, based on the implementation conditions. Another advantage of the proposed method is its applicability to uncertain Multi-Input Multi-Output (MIMO) systems. The loop performance in the presented algorithm can be also enhanced by appropriate selection of weighting matrices in a loop shaping procedure. Two examples are also presented to demonstrate the effectiveness of the method for multi-variable non-square uncertain systems, including a practical example of a purely delayed system. © 2025 ISA
Koofigar, H.R. ,
Esmaeili, F. ,
Saadat, A. ,
Esmaeili, F. ,
Saadat, A. ,
Koofigar, H.R. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025
The paper proposes a novel switched-capacitor multilevel inverter topology, designed for applications with low-voltage input supplies, such as photovoltaic power generation. The proposed multilevel inverter uses thirteen switches, four capacitors, four diodes, and only one DC source to produce 17level DC boosted output voltage. On the other hand, the voltage gain of the 17-level inverter is equal to eight. Low harmonics and high power quality (PQ) of output voltage and load current are some main advantages of the given topology, which makes it a grid-tied inverter. A self-balancing of the capacitor voltage, without any auxiliary circuits, and fewer components have been the additional features of the circuitry. The merits of the given 17-level inverter are assessed through a comparative analysis with recently presented converters. Additionally, the steady-state and dynamic performance of the suggested topology are validated through simulation in the PSCAD/EMTDC environment. © 2024 IEEE.
Journal of Process Control (09591524) 139
Surge is a form of dynamic instability created as an unstable pattern in the flow of fluid and can severely affect centrifugal compressor performance by causing fluctuations in flow and pressure parameters. Due to the heavy and costly damage that the surge may cause in various industrial processes such as petrochemical plants, it is necessary to design an appropriate control system to reduce the effect of this phenomenon. The problem of active surge control of a centrifugal compressor using the throttle control valve (TCV) in the presence of compressor parametric uncertainties as well as large demands on upstream and downstream loads is investigated in this work. The control objective was to design a robust control system that can stabilize the compressor over a wide operating range without knowing the upper bound for the uncertainties and load demand. The controller should also react quickly by generating a smooth control signal without saturating the control input. These objectives are achieved by designing a sliding mode controller along with a nonlinear disturbance observer. The performance of the proposed disturbance observer-based controller is evaluated under various operational and load conditions and the results are compared against fuzzy type 1, conventional sliding mode, and wavelet-based neural network robust adaptive controllers. The results show that the proposed method can tolerate large disturbances without any knowledge on the upper bound of the incident disturbance, both on the downstream pressure and upstream mass flow which is highly desirable in practice. The comparative study proves the efficacy of the proposed method using various performance measures. The study also confirms the superior robust performance and stability of the proposed method in front of matched and mismatched disturbances as well as model uncertainties especially close to the instability boundary. Although choosing a TCV actuator has made the control system design easier, the sensitivity of the control valve to flow coefficient and zero calibration under different operating ranges of the compression system is studied carefully and some recommendations for the users are provided. © 2024 The Authors
In this paper, the control performance of a bilateral teleoperation system is studied in the presence of a data injection attack. It is shown that even a simple data injection attack has the potential to deteriorate the system's guaranteed stability. Hence, a high-gain observer algorithm is proposed to detect data injection attacks. The stability of the closed-loop system with the passivity-based control law of robot manipulators, together with the proposed observer-based attack detection scheme, is proven using the ISS approach and small gain theorem. Finally, simulation results are presented, to demonstrate the accuracy and effectiveness of the proposed method. © 2024 IEEE.
IET Generation, Transmission and Distribution (17518687) 18(18)pp. 2987-2998
Herein, the load power control of the stand-alone photovoltaic-battery hybrid power system (HPS) has been investigated. The underlying HPS consists of a boost DC-DC converter, a non-isolated bidirectional half-bridge converter, a photovoltaic (PV) panel, and a battery pack. On the PV side, a disturbance observer-based finite-time terminal sliding mode control (FTSMC) is used to regulate the DC bus to the desired voltage, in the presence of irradiation variation and load changes. On the battery side, the load power control system is constructed, based on a model predictive control (MPC) algorithm, with constraints on state-of-charge (SOC) and maximum current value of the battery to improve the battery life cycle and high reliability of the system. To highlight the benefits of the closed-loop system, the analytical proofs and numerical analysis are presented from a comparative viewpoint. The experimentally derived results, by implementation on TMS320F28335 digital signal processing (DSP), are also presented and discussed for practical justification. © 2024 The Author(s). IET Generation, Transmission & Distribution published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
IEEE Access (21693536) 12pp. 192979-192989
This paper introduces a novel 21-level single-phase inverter based on switched-capacitor (SC) technology, featuring a reduced number of components and input DC voltage supply. The inverter is designed to operate with just one DC source to generate multiple voltage levels. Compared to recently developed SC-based multilevel inverter topologies, the proposed design offers several advantages, including (1) a lower number of semiconductor devices, (2) a higher output voltage gain, (3) self-balancing of capacitors, and (4) reduced voltage stress on the switches. Finally, computer simulations and laboratory tests were conducted to validate the performance of the proposed inverter. © 2013 IEEE.
Journal of Navigation (03734633) 76(6)pp. 709-730
This paper proposes a switched model to improve the estimation of Euler angles and decrease the inertial navigation system (INS) error, when the centrifugal acceleration occurs. Depending on the situation, one of the subsystems of the proposed switched model is activated for the estimation procedure. During global positioning system (GPS) outages, an extended Kalman filter (EKF) operates in the prediction mode and corrects the INS information, based on the system error model. Compared with previous works, the main advantages of the proposed switched-based adaptive EKF (SAEKF) method are (i) elimination of INS error, during the centrifugal acceleration, and (ii) high accuracy in estimating the attitude and positioning, particularly during GPS outages. To validate the efficiency of the proposed method in various trajectories, an experimental flight test is performed and discussed, involving a microelectromechanical (MEMS)-based INS. The comparative study shows that the proposed method considerably improves the accuracy in various scenarios. © The Author(s), 2024. Published by Cambridge University Press on behalf of The Royal Institute of Navigation.
This study introduces an algorithm for evaluating the stability of complex, interconnected systems with uncertainties. The approach simplifies the analysis by using a compositional certification strategy, which focuses on the properties of individual subsystems rather than the entire network. Initially, the algorithm examines the dissipative characteristics of the subsystems. It then incorporates the uncertainties of the connections to establish a compositional stability criterion for the network's stability assessment. This algorithm is computationally efficient compared to previous methods, making it appropriate for interconnected large-scale power systems. The efficiency of the presented procedure will be confirmed over a numerical analysis of the IEEE 14-bus test network, demonstrating its capability for assessing stability amidst uncertainties. © 2023 IEEE.
In a hybrid photovoltaic-battery system, the battery connects to photovoltaic renewable resource via a bidirectional DC-DC converter. Among the existing bidirectional converters, the half-bridge topology has been selected here, due to some advantages, as high efficiency and low size inductor. This study presents an H∞-based robust control for the non-isolated bidirectional half-bridge converter, by solving a mixed sensitivity problem, in a hybrid photovoltaic-battery system. The main advantage of the proposed technique is the ability to tackle a wide range of external disturbances and model uncertainties. The presented algorithm is simulated in Matlab/Simulink and evaluated under voltage and load changes. The numerical results show that the controller has the ability to maintain the half-bridge converter performance, under different perturbations. © 2023 IEEE.
Optics Express (10944087) 31(11)pp. 17250-17267
Piezoelectric deformable mirrors (DM) are benefited from the high accuracy and swift dynamics. The hysteresis phenomenon, which inherently exists in piezoelectric materials, degrades the capability and precision of the adaptive optics (AO) systems. Also, the dynamics of piezoelectric DMs make the controller design more complicated. This research aims to design a fixed-time observer-based tracking controller (FTOTC), which estimates the dynamics, compensates the hysteresis, and ensures tracking to the actuator displacement reference, in the fixed time. Unlike the existing inverse hysteresis operator-based methods, the proposed observer-based controller overcomes the computational burdens and estimates the hysteresis in real-time. The proposed controller tracks the reference displacements, while the tracking error converges in the fixed time. The stability proof is presented by two consecutive theorems. Numerical simulations demonstrate superior tracking and hysteresis compensation by the presented method, from a comparison viewpoint. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.
Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering (09596518) 237(9)pp. 1668-1677
In this article, robust model predictive control is proposed for discrete-time switched linear systems in the presence of external disturbances, model uncertainties and constraints on the states and input. To solve the problem, a mode-dependent average dwell time switching strategy is constructed in controller design procedure, with less limitations than the existing average dwell time switching. Using some mathematical tools, the model predictive control problem is turned into a feasible linear matrix inequality. The control algorithm is presented via two theorems, and the stability analysis is analytically presented, based on multiple Lyapunov function method. Compared with the previous studies, the underlying switched system may consist of stable and unstable subsystems, perturbed by model uncertainties and external disturbances. The simulation results are also given to study the effectiveness of the proposed robust model predictive control algorithm, from a comparison viewpoint. © IMechE 2023.
IEEE Journal of Emerging and Selected Topics in Power Electronics (21686785) 10(5)pp. 6084-6092
This article proposes a high performance with 13-step, switched-capacitor multilevel inverter (SCMLI). The gain factor of 6 is achieved, along with self-voltage balancing of capacitors. The suggested structure can be cascaded to generate any number of voltage steps with the inherent property of generating both positive and negative voltage steps. All the power switches withstand voltages lower than 50% of maximum output voltage. The number of power switches, the number of dc input sources, the voltage stress on the switches, and the power losses are reduced. Also, the presented inverter has a minimum cost function compared to the other similar structures. The performance of the proposed 13-step converter has been validated by the simulation, extracted by PSCAD/EMTDC, and also the experimental results, obtained from an implemented laboratory prototype. © 2013 IEEE.
IEEE Journal of Emerging and Selected Topics in Power Electronics (21686785) 9(3)pp. 2735-2744
The voltage control problem of self-exited switched reluctance generator (SRG) supplying a constant power load (CPL) is investigated here. Due to the uncertainties in SRG dynamic and load, conventional linear controllers may not solve the problem and voltage oscillation inevitably appears at high load powers. This article describes a series-damped passivity-based control (PBC) scheme, considering the dynamic performance of SRG, in the presence of CPL. The main objective is to achieve a large-signal stabilization of the output voltage of generator taking into account the uncertainties of SRG. The time-varying nature of back electromotive force (EMF) of SRG is considered by calculating the bound of damping injection terms. By an adaptation mechanism to deal with the time-varying inductance and back EMF, together with the proposed PBC, a large-signal active damping adaptive-passivity-based controller (APBC) is obtained to reduce the output voltage oscillations. The effectiveness of the proposed control scheme in stabilization in SRG and CPL and voltage ripple reduction is demonstrated, using a four-phase, 8/6 pole drive system. © 2013 IEEE.
IET Control Theory and Applications (17518644) 15(8)pp. 1115-1125
This paper presents the computation of the non-parametric uncertainty model for multi input multi output (MIMO) systems, which is described by normalized coprime factors (NCF) using the frequency response data of the system. This computation is accomplished by minimizing a υ-gap metric criterion. For this purpose, the problem is formulated to a convex optimization context, such that a semidefinite programming (SDP) can be implemented. Minimization constraints and the normality constraints of coprime factors are converted to linear matrix inequalities (LMI). Thus, by convex optimization algorithms, the semidefinite programming will be optimized. The proposed method can also be used for non-square multi input multi output systems in a conservative assumption. So, through the first process of optimization, the frequency responses of the normalized coprime factors are derived. Finally, to evaluate the performance of the proposed method in the computation of the normalized coprime factors of a system, the simulated results of this method are compared with those obtained by the other methods for two types of systems. © 2021 The Authors. IET Control Theory & Applications published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology
Control Engineering Practice (09670661) 107
In this paper, a novel observer-based force control scheme is proposed to guarantee the position and force tracking in nonlinear teleoperation systems, subject to constant communication time delay. Stability of the teleoperation system is analytically proved using the Lyapunov stability theorem. Enough condition for asymptotic convergence of the force and position are derived. The transparency is also improved by force tracking capability of the system. The teleoperation controller is then applied to a pair of planar 2-DOF robots, connected via a communication channel with constant time delay. The experimental and simulation results demonstrate the effectiveness of the proposed control algorithm, in force estimation and dealing with time delay. © 2020 Elsevier Ltd
Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering (09596518) 235(4)pp. 532-539
This article addresses the adaptive-based robust output feedback tracking control for robot manipulators with friction and alternating unknown loads. A switched nonlinear system is first established to model the friction and parameter variations, caused by the load change. Under arbitrary load changings, an adaptive (Formula presented.) tracking control strategy is proposed to ensure link position tracking, in the presence of uncertainties and external disturbances. Then, for bounded external disturbances, a novel robust adaptive output tracking control strategy is developed, which guarantees all the closed-loop signals are bounded and tracking error is driven to zero. Unlike some previous studies, the proposed algorithms do not require velocity measurements, and the unknown switched parameters and disturbances are neither required to be periodic nor to have known bounds. A simulation study is also given to demonstrate the analytically proved properties of the proposed schemes. © IMechE 2020.
IET Power Electronics (17554543) 14(16)pp. 2597-2609
It is known that constant power load (CPL) may cause a negative impedance, which seriously affects the stability of power system. In this paper, a new control algorithm for DC–DC buck converter feeding unknown CPL is proposed. First, under the assumption of known extracted power load, the standard passivity–based control (PBC) is presented to reshape the system energy and compensate for the negative impedance and a proportion-integration (PI) action around passive output is added to improve disturbance rejection performance, which forms the PBC plus PI (PBC+PI). Then, a parameter estimation algorithm is developed, based on immersion and invariance (I&I) technique, in order to online estimate the extracted power load. In the next step, the online estimation scheme is adopted to construct an adaptive strategy. Finally, the stability analysis of the cascaded system containing a closed-loop control system and observer error dynamics is conducted. Simulation and experimental results are demonstrated to validate the performance of the proposed controller. © 2021 The Authors. IET Power Electronics published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology
Control Engineering Practice (09670661) 115
In this paper, the problem of voltage regulation of DC–DC buck converter with unknown constant power load (CPL) and input voltage is addressed. A power shaping controller (PSC) based on the passivity theory is proposed to stabilize this system. In addition, borrowing immersion & invariance (I&I) technique, an observer can be designed to estimate CPL and input voltage simultaneously. By combining PSC with I&I observer, an adaptive control scheme is achieved. Besides, the estimate of the domain of attraction is given to rigorously guarantee the convergence property by virtue of the invariant set theory. Then, the locally asymptotic stability of the closed-loop system is established. Finally, the simulation and experimental results show the effectiveness of the proposed control method. © 2021 Elsevier Ltd
2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025
This paper presents a new robust design approach to control the frequency of a two-microgrid cluster together with the power of the coupling line. To this end, a two-microgrid cluster including both dispatchable and non-dispatchable source is considered as a study case. The non-dispatchable sources cause power imbalance due to stochastic behavior. The stochastic behavior of these sources leads to the frequency deviation. Furthermore, it affects the power of the coupling line connecting two microgrids. Thereby, a two-level design process is addressed. It includes inner and outer optimization. The outer level determines the weighting functions for the inner level. The inner level designs the robust regulator by solving an optimization problem constrained by a linear matrix inequality in three stages. The first stage, the state feedback is determined in order to provide robust behavior. The second stage, an observer is obtained to estimate the states used for the state feedback. The last stage, the controller is formed using state feedback as well as the state observer. Then, a series of simulations are carried out using the designed controller. The results show that the robust controller can improve the operation of microgrids in comparison with the conventional proportional-integral controller. © 2020 IEEE.
Sustainable Energy, Grids and Networks (23524677) 21
This paper presents a novel strategy for output power control of a hybrid energy system, composed of renewable energy sources (wind and photovoltaic), a battery bank and a variable load. Developing an energy management strategy, the hybrid energy system is described here as a switched nonlinear system with unknown parameters. Then, an adaptive control strategy is proposed to satisfy the total power demand in different conditions, under arbitrary switching. The proposed control law only depends on angular speed and current, without requiring the wind measurements. The analytical stability proof is given, based on the common Lyapunov function method. The simulation results are also presented and discussed to demonstrate the performance of the proposed method, for a typical hybrid energy system. © 2019
Control Engineering and Applied Informatics (14548658) 21(1)pp. 70-78
In this paper, the maximum power point tracking (MPPT) and the load voltage control of a Hybrid Power System (HPS) has been investigated. The underlying HPS consists of a boost converter, a Bidirectional DC-DC converter (BDC), a photovoltaic (PV) panel, and a battery. The integral sliding mode controller (ISMC) is proposed For MPPT. The load voltage control system is based on the use of a double-loop controller, an inner one to control the current of the battery by the sliding mode control (SMC) and the outer one to control the load voltage by a PI controller. Dynamic equations of the system are derived from the "state-space averaging method". Afterwards, a method for obtaining the load resistance is presented to improve the dynamic response. Then, the results of the proposed controllers for MPPT and the load voltage control by means of simulations using the Matlab/Simulink software are discussed. The experimentally derived results, by implementation on SPARTAN XC3S400 chip, are also given for justification. © 2019, Control Engineering and Applied Informatics Journal.
Koofigar, H.R. ,
Ekramian, M. ,
Mahzounieh, A. ,
Mahzounieh, A. ,
Koofigar, H.R. ,
Ekramian, M. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 1216-1220
The aim of this paper is to propose an identification scheme for linear switched systems with state space description. The method consists of two stages: First, output matrix elements are identified by Kaczmarz Algorithm and then by k-means clustering algorithm, switching time is estimated; Second, by passing the estimated switching time to an adaptive observer in serial-parallel form, input and state matrices are estimated. Identification method is tested on numerical simulation. © 2019 IEEE.
International Journal of Systems Science (00207721) 49(3)pp. 486-495
This paper investigates the problem of adaptive output feedback tracking for uncertain switched nonlinear systems, under arbitrary switching. First, an adaptive output feedback controller is designed, which ensures the boundedness of all the closed-loop signals. Then, a novel adaptive-based robust output feedback control is proposed to drive the tracking error to zero, in which the bound of disturbances is not required to be known in advance. Both control algorithms are based on the common Lyapunov function method, without any restrictions on dwell time. To evaluate the performance of the proposed output feedback control schemes, a numerical example is presented and discussed. © 2017 Informa UK Limited, trading as Taylor & Francis Group.
International Journal of Systems Science (00207721) 49(13)pp. 2784-2796
The mechanical impedance of the human arm can be measured to quantitatively assess the motor function. In this paper, an adaptive least square estimation method is proposed for online measurement of the mechanical impedance of the arm, without force or acceleration sensors, which extremely reduces the expenses and complexity of rehabilitation robots. The proposed strategy may also be used for monitoring the dynamic changes of the mechanical impedance. Estimation of time-varying force is also the other capability of the algorithm. The closed-loop stability of the system is analytically shown using the Lyapunov stability theorem. To show the applications of the proposed scheme, two main scenarios are described which can be used for the rehabilitation robots to assess the motor recovery of the patients undergoing the rehabilitation sessions. To validate the scheme, a 2-DOF manipulator is adopted to illustrate the accuracy of the impedance and force estimations in noiseless and noisy conditions. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.
Journal of Marine Science and Technology (Taiwan) (10232796) 26(1)pp. 1-10
Due to the important role of hydrodynamic coefficients in the control and guidance of an autonomous underwater vehicle (AUV), sensitivity analysis is proposed here, as a preliminary step to motion control design. Taking the standard maneuvers, including turning circle and horizontal and vertical zigzag, the sensitivity of various hydrodynamic coefficients with respect to velocities and position is determined. Such analyses are then used to classify the model parameters into three categories, as non-sensitive coefficients, coefficients with low influence on the motion and more sensitive coefficients.
International Journal Of Renewable Energy Research (13090127) 8(3)pp. 1411-1420
In this paper, the importance of taking into account power losses in the design of sliding mode controller (SMC) for hybrid power source (HPS) has been investigated. The underlying HPS consists of a boost converter, a bidirectional converter, a photovoltaic (PV) panel, and a battery. Dynamic equations of the system are derived based on the state-space averaging method. Afterward, a method to obtain power losses is provided. A robust control methodology, based on the SMC is then proposed to take the power losses into account. Asymptotic stability of the proposed method is ensured, using the Lyapanov stability theorem. To verify the robustness properties of the closed-loop system, with respect to the input voltage variation and load resistance, some simulation studies are presented and discussed. The results show that power losses should be considered in the controller design for an HPS. The experimental results, by implementation on SPARTAN XC3S400 chip, are also given for justification. © 2018, International Journal of Renewable Energy Research.
Namazi, M.M. ,
Rashidi, A. ,
Koofigar, H.R. ,
Saghaiannejad, S.M. ,
Ahn, J. Journal of Electrical Engineering and Technology (19750102) 12(1)pp. 134-144
This paper presents an adaptive control strategy for the speed control of a four-phase switched reluctance motor (SRM) in automotive applications. The main objective is to minimize the torque ripples, despite the unstructured uncertainties, time-varying parameters and external load disturbances. The bound of perturbations is not required to be known in the developing of the proposed adaptive-based control method. In order to achieve a smooth control effort, some properties are incorporated and the proposed control algorithm is constructed using the Lyapunov theorem where the closed-loop stability and robust tracking are ensured. The effectiveness of the proposed controller in rejecting high perturbed load torque with smooth control effort is verified with comparing of an adaptive sliding mode control (ASMC) and validated with experimental results. © The Korean Institute of Electrical Engineers.
Journal Of Intelligent And Robotic Systems (15730409) 85(2)pp. 331-352
In this paper, the problem of identification-based robust motion control of an Autonomous Underwater Vehicle (AUV) is investigated. The unknown system parameters are estimated by using an adaptive parameter identifier, whose gains are optimized by Particle Swarm Optimization (PSO) algorithm. Removing the trial and error procedure and ensuring the convergence property together with fast response, are the benefits of such identification scheme. On the other hand, the system uncertainties, hydrodynamic parameter variations and external disturbances which affect the identified dynamical model, are also taken into account. The cross-coupling effects between subsystems are also considered as model uncertainties. Such uncertain model is then adopted in control synthesis procedure, in the steering and diving modes. In order to achieve the robust stability and performance, two robust control strategies are presented here to solve the motion control problem. First, an H∞ mixed sensitivity problem is formulated in which the weighting functions are selected based on an optimization criterion, by using PSO algorithm. Controller order reduction is also applied to the resulting diving and steering controllers, using the Hankel norm approximation. Then, an Adaptive Sliding Mode Control (ASMC), whose sliding surface coefficients are optimized by PSO algorithm, is developed for the identified AUV model. Possessing the robustness properties with respect to system perturbations, the developed Sliding Mode Control (SMC) removes the complexity of uncertain model representation and the limitations on choosing the weighting functions in the H∞ control problem. The upper bounds of perturbations are not required to be known in the proposed control schemes. The simulation results are also presented to demonstrate the performance of the proposed identification-based control methods. © 2016, Springer Science+Business Media Dordrecht.
Archives of Electrical Engineering (14274221) 66(3)pp. 459-474
A robust auxiliary wide area damping controller is proposed for a unified power flow controller (UPFC). The mixed H2 /H∞ problem with regional pole placement, resolved by linear matrix inequality (LMI), is applied for controller design. Based on modal analysis, the optimal wide area input signals for the controller are selected. The time delay of input signals, due to electrical distance from the UPFC location is taken into account in the design procedure. The proposed controller is applied to a multimachine interconnected power system from the IRAN power grid. It is shown that the both transient and dynamic stability are significantly improved despite different disturbances and loading conditions.
IEEE Transactions on Aerospace and Electronic Systems (00189251) 53(5)pp. 2534-2543
In this paper, the robust control problem for spacecraft formation flying in virtual structure algorithm is addressed. The effects of external disturbances, model uncertainties, sensor noises, and actuator saturation are taken into account. A robust controller based on μ-synthesis is first designed to overcome the environmental disturbances. To obtain a control law with lower order, an H∞-based linear matrix inequality controller is designed, using the linearized model with uncertainties. Then, a robust adaptive controller, based on the Lyapunov stability theorem, is presented to overcome a broader range of model uncertainties, which also guarantees the stability. From a comparison viewpoint, the numerical results are also demonstrated to show the performance of the robust controllers in tracking the desired attitude and position. © 2017 IEEE.
International Journal of Artificial Intelligence (09740635) 15(1)pp. 163-179
Echo State Networks (ESN) are a special form of recurrent neural networks (RNNs), which allow for the black box modeling of nonlinear dynamical systems. A unique feature of an ESN is that a large number of neurons (the “reservoir”), whose synaptic connections are generated randomly, is used in such that only the connections from the reservoir to the output modified by learning. The computation of optimal weights can then be achieved by a simple linear regression in an offline manner. ESNs have been applied to a variety of tasks from time series prediction to dynamic pattern recognition with great success. In many tasks, however, an online adaptive learning of the output weights is required. Harmony Search (HS) algorithm shows good performance when the search space is large. Here we propose HS algorithm for training echo state network in an online manner. In our simulation experiments, the ESNs are trained for predicting of three different time series including Mackey-Glass, Lorenz chaotic and Rossler chaotic time series with four different algorithms including Recursive Least Squares (RLS-ESN), Particle Swarm Optimization (PSO-ESN), and our proposed methods (HS-ESN and HS-RLS-ESN). Simulation results show that HS-ESN is significantly the fastest algorithm for training ESN whereas can effectively meet the requirements of the output precision. HS-RLS-ESN algorithm firstly uses HS to close to solution region then it uses RLS to obtain less error. HS-RLS-ESN is slower than HS-ESN and faster than RLS-ESN, but its generality power is very close to RLS-ESN. © 2017 [International Journal of Artificial Intelligence].
Journal of Theoretical and Applied Mechanics (14292955) 54(3)pp. 987-1000
In this paper, adaptive control for a class of uncertain nonlinear systems with input constraints is addressed. The main goal is to achieve a self-regulator PID controller whose coefficients are adjusted by using some adaptive fuzzy rules. The constraints on the control signal are taken into account as a saturation operator. The stability of the closed-loop system is analytically proved by using the Lyapunov stability theorem. The proposed method is then applied to a surface vessel with uncertain dynamic equations. The simulation results show the effectiveness of the proposed control strategy.
ISA Transactions (00190578) 60pp. 285-293
The problem of maximum power point tracking (MPPT) in photovoltaic (PV) systems, despite the model uncertainties and the variations in environmental circumstances, is addressed. Introducing a mathematical description, an adaptive sliding mode control (ASMC) algorithm is first developed. Unlike many previous investigations, the output voltage is not required to be sensed and the upper bound of system uncertainties and the variations of irradiance and temperature are not required to be known. Estimating the output voltage by an update law, an adaptive-based H∞ tracking algorithm is then developed for the case the perturbations are energy-bounded. The stability analysis is presented for the proposed tracking control schemes, based on the Lyapunov stability theorem. From a comparison viewpoint, some numerical and experimental studies are also presented and discussed. © 2015 ISA. Published by Elsevier Ltd. All rights reserved.
2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 484-489
In this paper, a sliding surface is defined based on the inductor current to construct a robust controller for Maximum Power Point Tracking (MPPT) in the photovoltaic (PV) systems. An adaptive incremental conductance algorithm has been used to obtain the set point of the controller. An improvement is achieved by this combination, especially in fast irradiance variations. The robust stability of the method is proved using the Lyapunov stability theorem. A comparative study is also made to highlight the benefits of the proposed algorithm. The features of this controller, in terms of robustness against the irradiance variations, are demonstrated by theoretical analysis, simulations and an experimental study. The results demonstrate that the proposed controller can be implemented effectively and economically with high MPPT efficiency. © 2016 IEEE.
Koofigar, H.R. ,
Malekzadeh, M. ,
Abolvafaie, M. ,
Abolvafaie, M. ,
Koofigar, H.R. ,
Malekzadeh, M. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 90-95
To improve the tracking control performance, in the presence of parametric uncertainties, for an autonomous underwater vehicle (AUV), the sensitive parameters are first identified, using the direct sensitivity analysis method. Then, an adaptive second order sliding mode controller is proposed to ensure the robust stability and performance, without any a priori knowledge on the upper bound of perturbations. To this end, a proportional integral derivative (PID) structure is adopted, as the sliding surface. The unknown sensitive parameters are estimated by some adaptive mechanisms. On the other hand, the second order sliding mode control (2-SMC) is developed to neutralize the effects of unstructured uncertainties and disturbances. The closed loop stability is shown, using the Lyapunov stability theorem, and verified by various numerical simulations. © 2016 IEEE.
Journal Of Engineering Science And Technology (18234690) 11(11)pp. 1528-1542
In this paper, the design of command to line-of-sight (CLOS) missile guidance law is addressed. Taking a three dimensional guidance model, the tracking control problem is formulated. To solve the target tracking problem, the feedback linearization controller is first designed. Although such control scheme possesses the simplicity property, but it presents the acceptable performance only in the absence of perturbations. In order to ensure the robustness properties against model uncertainties, a fuzzy adaptive algorithm is proposed with two parts including a fuzzy (Mamdani) system, whose rules are constructed based on missile guidance, and a so-called rule modifier to compensate the fuzzy rules, using the negative gradient method. Compared with some previous works, such control strategy provides a faster time response without large control efforts. The performance of feedback linearization controller is also compared with that of fuzzy adaptive strategy via various simulations. © School of Engineering, Taylor’s University.
Koofigar, H.R. ,
Ekramian, M. ,
Dehghan, S.A.M. ,
Dehghan, S.A.M. ,
Koofigar, H.R. ,
Ekramian, M. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 102-106
This paper presents a nonlinear 4-channel bilateral teleoperation system, without using force sensor. In the design procedure, the adaptive control laws estimate and compensate the exerted forces on both master and slave robots. The estimated forces are then used in a control loop for modifying the trajectory of both robots to meet the full transparency condition. The stability and the transparency of the teleoperation system are analyzed, based on the Lyapunov theorem. Some simulations are also presented for a two planar two-degree of freedom manipulator to show the efficiency of the proposed control algorithm. © 2016 IEEE.
Journal of Electrical Engineering and Technology (19750102) 11(5)pp. 1057-1062
In this paper, an advanced and modified MRAS technique is utilized for controller design in electric power systems. The weighting factors of the proposed MRAS are tuned by using PSO. This optimal-adaptive controller is also normalized by normalization techniques to guarantee the system stability. The proposed MRAS then is applied to design STATCOM stabilizer and UPFC power flow controller. STATCOM stabilizer is a regulatory controller, while the power flow controller of UPFC is a tracking one. Therefore, the ability of the proposed MRAS technique to design regulatory and tracking controllers is investigated. In order to indicate the effectiveness of the proposed method, it is evaluated against the conventional methods. Simulation results demonstrate the validity of the method, under uncertainties and different disturbances. © The Korean Institute of Electrical Engineers.
Koofigar, H.R. ,
Malekzadeh, M. ,
Abolvafaie, M. ,
Abolvafaie, M. ,
Koofigar, H.R. ,
Malekzadeh, M. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 432-437
Sensitivity analyses in the turning circle and zigzag maneuvers, as two main standard ones, are proposed here as a preliminary step to motion control design for an Autonomous Underwater Vehicle (AUV). The most effective parameters of the AUV are then adopted to be estimated by some adaptation mechanisms. Adaptive sliding mode control is developed to ensure the robust stability and performance, without a priori knowledge about the bound of perturbations. A simulation study is also presented to demonstrate the effectiveness of the method. © 2015 IEEE.
Journal of Mechanical Science and Technology (1738494X) 29(11)pp. 4901-4911
This paper presents an adaptive-based fault detection and isolation scheme for a general class of robot manipulators, with characterizing the isolability conditions. The proposed algorithm consists of a nonlinear adaptive fault detection estimator and a bank of fault isolation estimators to determine the types of faults, which may be incipient or abrupt, while the fault parameter function may be time-varying. To demonstrate its effectiveness, the method is applied to a two-link robot manipulator and the simulation results are presented and discussed. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.
Nonlinear Dynamics (0924090X) 79(2)pp. 1457-1468
In this paper, the control problem of underactuated systems with mismatched and matched uncertainties is addressed. Adaptive fuzzy backstepping controller is proposed to solve the problem, ensuring the robustness against uncertainties and disturbances. Taking a general class of underactuated robotic systems into account, the nonlinear dynamical equations are first transformed to the so-called cascade form and then, an adaptive-based controller is constructed using the capability of fuzzy logic to tackle the perturbations. From the analytic point of view, the closed loop stability is ensured using the Lyapunov stability theorem. To demonstrate the effectiveness of the method, the proposed controller has been applied to a two-wheeled self-balancing robot with three degrees of freedom, and also to a pendubot with two degrees of freedom. In order to highlight the superiority of the proposed algorithm, the performance is compared with that of an existing robust strategy. © 2014, Springer Science+Business Media Dordrecht.
International Journal of Control, Automation and Systems (20054092) 12(1)pp. 169-176
This paper is concerned with the tracking control problem of robotic systems perturbed by time-varying parameters, unmodelled dynamics and external force (and moment) disturbances. The upper bound of system uncertainties and disturbances is not required for controller design. Also, no limitations are assumed on the speed of variation and the magnitude of unknown parameters and perturbations. An adaptive algorithm with simplicity and universality properties is proposed to ensure robust tracking. Presenting the closed loop stability proof analytically, the tracking controller is applied to a two-link robot manipulator and the simulation results are demonstrated to show the effectiveness of the method. © 2014 Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag Berlin Heidelberg.
2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 141-146
In this paper, by choosing the islanded structure for DER, the problem of voltage and frequency control in micro grids is discussed. The proposed control scheme has been used as a feed forward compensation strategy to reduce the nonlinear effects and to compensate for the load dynamics. Thus, the mathematical islanded model of DER system has been introduced and then, the voltage and frequency controllers have been designed to achieve fast and stable response and also zero steady state error. The operation of system in different load conditions is checked by Matlab-Simulink software. The simulation results show the robust operation of closed loop system composed with designed controller. © 2014 IEEE.
Journal of Theoretical and Applied Mechanics (14292955) 52(4)pp. 959-969
In this paper, a novel fuzzy-integral-sliding controller (FISC) is designed for coupled nonlinear two-input two-output (TITO) systems. Decomposing the original system into two subsystems, the coupling effects are modelled as uncertainties. In order to ensure the robustness properties with respect to system uncertainties and external disturbances, the sliding mode technique with a proportional integral (PI) sliding surface is adopted. On the other hand, to avoid the chattering phenomenon, the Takagi-Sugeno fuzzy rules are incorporated into the control algorithm, which forms a fuzzy sliding controller. The stability analysis is also presented based on the Lyapunov stability theorem. The proposed FISC is then applied to control the elevation and azimuth angles of Humusoft CE150, as a two degree of freedom (DOF) laboratory helicopter model with highly cross-coupled dynamics. The simulation results are also presented to demonstrate the performance of the proposed control scheme. © 2014, Polish Society of Theoretical and Allied Mechanics. All rights reserved.
Journal Of Engineering Science And Technology (18234690) 9(2)pp. 261-272
In this paper, the problem of designing an optimal control algorithm for rolling processes is addressed. Deriving a mathematical model for a general class of rolling mills, the optimal control problem is defined. In the design procedure, time delays in thickness measurment and control input are taken into account. The proposed strategy significantly improves the results of previous investigations from practical point of view. Simulation results are also studied to highlight the effictiveness of the method. © School of Engineering, Taylor's University.
Biomedical Signal Processing and Control (17468108) 14pp. 291-296
The early detection of abnormal heart conditions is vital to identify heart problems and avoid sudden cardiac death. The people with similar heart conditions almost have similar electrocardiogram (ECG) signals. By analyzing the ECG signals' patterns one can predict arrhythmias. Since the conventional methods of arrhythmia detection rely on observing morphological features of the ECG signals which are tedious and very time consuming, the automatic detection of arrhythmia is more preferable. In order to automate detection of heart diseases an adequate algorithm is required which could classify the ECG signals with unknown features according to the similarities between them and the ECG signals with known features. If this classifier can find the similarities precisely, the probability of arrhythmia detection is increased and this algorithm can become a useful means in laboratories. In this article a new classification method is presented to classify ECG signals more precisely based on dynamical model of the ECG signal. In this proposed method a fuzzy classifier is constructed and its simulation results indicate that this classifier can segregate the ECGs with an accuracy of 93.34%. To further improve the performance of this classifier, genetic algorithm is applied where the accuracy in prediction is increased up to 98.67%. This proposed method increases the accuracy of the ECG classification regarding more precise arrhythmia detection. © 2014 Elsevier Ltd. All rights reserved.
Madani, S.M. ,
Koofigar, H.R. ,
Arashnia A. ,
Sharafoddin A. ,
Arashnia A. ,
Madani, S.M. ,
Koofigar, H.R. ,
Sharafoddin A. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 470-475
Isolated single-stage, single-switch power factor correction have some advantages, such as fewer element count, higher efficiency, and lower oscillation output. Usually, linear controllers with limited bandwidth frequency are used for these types of converters. This controller degrades the converters performance after any sudden load change. The time required by the controller to respond to such a change is at least 2 cycles of input voltage, which cause defects such as intensive output the bulk capacitor voltage deviation. Conventional solution requires a large and costly capacitor. This paper proposes a 3 dimensional sliding surface (instead of sliding line), to improve the converter's performance during sudden load changes. The proposed method controls the switching frequency by adjusting bandwidth hysteresis modulation. Finally, the performance improvement of the method is verified by simulation. © 2014 IEEE.
Journal of Marine Science and Technology (Taiwan) (10232796) 22(4)pp. 455-462
This paper addresses the motion control problem of autonomous underwater vehicles (AUVs) perturbed by unknown hydrodynamic coefficients, unmodelled dynamics and environmental disturbances. The proposed algorithm consists of an adaptive subcontroller to tackle the parametric uncertainties and a robust term to vanish the effects of unstructured uncertainties and disturbances. The resulting robust adaptive controller ensures the convergence of tracking error, without any assumption on the upper bound of perturbations in the design procedure. The closed loop stability is shown, using the Lyapunov stability theorem, and verified by various simulations.
International Journal of Precision Engineering and Manufacturing (22347593) 15(3)pp. 391-397
This paper presents an observer based actuator fault detection algorithm for an electro hydraulic system. A nonlinear observer is first designed which is robust with respect to model uncertainties and external disturbances. Then, the developed observer is applied for fault detection in a hydraulic actuator with unknown friction forces. This paper focuses on the small internal leakage that defined as an actuator fault and the leakage is detected by an adaptive threshold. In addition to theoretical analysis and closed loop stability proofs, simulation results are also included to show the effectiveness of the method in the presence of system uncertainties and disturbances. © 2014 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.
Mediterranean Journal of Measurement and Control (17439310) 10(4)pp. 316-323
This paper is concerned with the second order sliding mode (SOSM) control design for a class of multi-inputmulti-output(MIMO) uncertain nonlinear systems.The design objectives of the controller are to stabilise the coupled MIMO systems and asymptotically tracking a specified trajectory. The MIMO system is decomposed into some subsystems and the cross-coupling effects between subsystems are considered as system uncertainty. In order to ensure the robustness properties with respect to system uncertainties and external disturbances, sliding mode technique with a proportional integral (PI) sliding surface is adopted. The proposed controller ensures the closed loop stability, as shown by using the Lyapunov stability theorem. The performance of the control strategy is evaluated by applying to a two degree-of-freedom (DOF) quadruple-tank model with cross-coupled dynamics. Simulation results verify the effectiveness of the proposed control algorithm despite the perturbations. Copyright © 2014 SoftMotor Ltd.
Mediterranean Journal of Measurement and Control (17439310) 10(3)pp. 252-259
In this paper, the control problem of underactuated systems in the presence of external disturbances and time varying model uncertainties is considered. Ensuring the stability and robust performance against uncertainties and disturbances arc the main problems in such systems. An adaptive fuzzy sliding mode controller (AFSMC) is proposed to solve the problem, satisfying the robustness properties against the perturbations. The designed controller can be applied to a wide class of underactuated systems with fewer restrictions, compared with many pervious works. To evaluate the performance of proposed algorithm, it is applied to an underactuated inverted pendulum and a Translational Oscillator/Rotational Actuator (TORA) system with two degrees of freedom. The simulation results are compared with a conventional method to demonstrate the effectiveness of the proposed strategy. The results show that the proposed controller guarantees the stability and robustness against time varying uncertainties and disturbances. Copyright © 2014 SoftMotor Ltd.
JVC/Journal of Vibration and Control (10775463) 19(13)pp. 2046-2053
This paper presents a novel adaptive-based vibration control algorithm for smart structures, despite the model parameter variations, unstructured uncertainties, and environmental disturbances. The rate of vibration suppression can be managed in the proposed method, by taking a desired exponential decaying trajectory. Since the proposed method is established by taking various perturbations into account, it can be applied to a wide class of structures without any conservative hypotheses. The stability analysis is presented based on the Lyapunov's direct method. In order to verify the effectiveness of the method, numerical analyses are presented and discussed by applying the developed vibration control methodology to a smart beam. © 2012 The Author(s).
2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 69-74
In this paper, by choosing the islanded structure for DER, the problem of voltage and frequency control in micro grids is discussed. The proposed control scheme has been used as a feed forward compensation strategy to reduce the nonlinear effects and to compensate for the load dynamics. Thus, the mathematical islanded model of DER system has been introduced and then, the voltage and frequency controllers have been designed to achieve fast and stable response and also zero steady state error. The operation of system in different load conditions is checked by Matlab-Simulink software. The simulation results show the robust operation of closed loop system composed with designed controller. © 2013 IEEE.
Research Journal of Applied Sciences, Engineering and Technology (discontinued) (20407459) 5(1)pp. 280-285
Transient stability is one of the main issues in the field of power systems. On the other hand, using FACTS devices has been proposed for the purpose of maximizing the lines conductivity given the restrictions involved, including the issue of stability. This study seeks to take steps towards the improvement of a multi-machine power system stability in faulty conditions, using two FACTS devices including TCSC and SVC. The control system for the FACTS devices is constructed here based on the so called energy function method. Meanwhile, in order to achieve a prescribed optimal performance, the coefficients of the designed controller are tuned by PSO algorithm. Possessing the theoretical analysis, the simulation results are also demonstrated to show the performance of the proposed control algorithm. © Maxwell Scientific Organization, 2013.
2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 152-157
In this paper, a model predictive control is presented and applied to a two wheeled self balancing robot. This robot is known as a three-degree-of-freedom mobile robot with multivariable underactuated dynamics. The dynamic equations of the system are first introduced and the inputs and outputs are assigned. Then, by using a compensator block in sequential closing loop method, the original system is transformed into two subsystems. The model predictive controller is designed for maintaining robot in balance despite the external disturbances. The robustness of the method is evaluated in the presence of sinusoidal and step-like disturbances. The simulation results are also presented and discussed using Matlab software. © 2013 IEEE.
Journal of Theoretical and Applied Mechanics (14292955) 51(3)pp. 533-541
The problem of active vibration suppression in a wide class of smart structures is addressed. The dynamical model of a structure may be perturbed by uncertain time-varying parameters and external disturbances. A novel adaptive-based control algorithm is presented here to satisfy robustness properties with respect to model uncertainties and environmental disturbances. Reflecting practical situations, the upper bound of perturbations is not required for controller design. The analytical stability of a closed-loop system is presented based on the Lyapunov stability theorem. Furthermore, numerical analysis is also provided to show the effectiveness of the proposed method.
2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 192-196
Adaptive motion control of a general class of autonomous underwater vehicles (AUVs) in the presence of model uncertainties and environmental disturbances is addressed. The both parametric and unstructured uncertainties are incorporated into the mathematical model, due to the variations in hydrodynamic and damping coefficients. An adaptive-based control algorithm is first constructed to tackle the parametric model uncertainties. Then, a robustifying term is incorporated into the control law, ensuring the robustness of the method with respect to unstructured uncertainties and external disturbances. Without any pre-assumption on the periodicity and the upper bound of unknown parameters and disturbances, the robust stability is shown to be achieved, using the Lyapunov stability theorem. The proposed robust adaptive controller is then applied to a known AUV to evaluate the performance of the method. © 2012 SICE.
International Journal of Innovative Computing, Information and Control (13494198) 8(9)pp. 6317-6327
This paper addresses the chaos control of uncertain chaotic nonlinear gyros with unknown parameters. In general, the underlying class of gyros may be perturbed by external disturbances with different sources. Depending on the characteristics of un¬certain parameters and disturbances, two different adaptive-based control algorithms are proposed. In the first method, an adaptive H ∞ controller is designed when the external disturbances are square-integrable. The other proposed scheme is based on developing a pure adaptive controller, in which the parameters and disturbances can be time-varying with unknown bounds. In both methods, the prescribed robustness property is guaranteed and the stability analysis is presented, using the Lyapunov stability theorem. Simulation studies show that the goal of chaos control is achieved despite the system uncertainties and external disturbances. © 2012 ICIC International.
International Review of Mechanical Engineering (19708734) 6(2)pp. 284-290
The control problem of boiler unit, as one of the main components of power plants, is addressed. The mathematical model of a boiler system can be represented as a multiple input multiple output (MIMO) dynamical system. Inaccurate modeling of such complex nonlinear system is taken here as system uncertainty. Taking the system parametric uncertainties into account, a state-space representation of the model is derived, to be adopted in designing a robust adaptive controller. The performance of the proposed method is compared with that of a sliding mode control algorithm. Simulation studies show the effectiveness of the developed controller to achieve the desired robust performance. © 2012 Praise Worthy Prize S.r.l. All rights reserved. All rights reserved.
Research Journal of Applied Sciences, Engineering and Technology (discontinued) (20407459) 3(9)pp. 1052-1056
This study focuses on the necessity of designing state observers to be used in controller synthesis for rolling processes. This is motivated by the fact that using several kinds of sensors for measuring all of process variables is technically and economically avoided. On the other hand, using exact measurement in feedback control systems could considerably improve the quality of products. In other word, there is a trade-off between high quality and the implementation limitations, managed here by developing rolling state observers. The proposed observers estimate the states not measured directly by the installed sensors. This technique is applicable to both hot rolling and cold rolling processes. Simulation results demonstrate the performance of the proposed estimation algorithm. © Maxwell Scientific Organization, 2011.
International Review on Modelling and Simulations (19749821) 4(6)pp. 3425-3429
This paper presents a novel approach for improving the performance of rolling mills, by designing an estimation-based control algorithm. This is motivated by the fact that using several kinds of sensors for measuring all of process variables is technically and economically avoided. On the other hand, high quality may be obtained by some control algorithms at the expense of using many sensors for exact measurement. Therefore, there is a trade-off between high quality and technical limitations which should be managed in such a manner that the best result is achieved. The proposed algorithm satisfies both objectives including high quality and low production costs by developing reduced order state observers. The designed estimation-based control technique facilitates combining sensor-based and sensorless design methodologies. This technique is applicable to both hot rolling and cold rolling processes. A typical cold rolling process is adopted here to evaluate the effectiveness of the proposed estimation method. Simulation results show that the desired performance can be achieved using the developed strategy. © 2011 Praise Worthy Prize S.r.l. All rights reserved.
The synchronization problem for a general class of uncertain chaotic systems is addressed. The underlying systems may be perturbed by unknown time-varying parameters, unstructured uncertainties, and external disturbances. Meanwhile, the time-varying parameters and disturbances are neither required to be periodic nor to have known bounds. Assuming the disturbances are L2 signals, an adaptive control incorporated with H∞ control technique is employed to construct a robust adaptive synchronization algorithm. Then, removing such assumption, a novel adaptive-based method is developed to achieve the goal of synchronization. In order to demonstrate the effectiveness of the proposed algorithms, such methods are applied to solve the synchronization problem of uncertain chaotic Chua's circuits. © 2011 American Institute of Physics.
International Journal of Precision Engineering and Manufacturing (12298557) 12(3)pp. 393-403
In this paper, the unified gauge-tension control problem is formulated by defining the exit strip thickness of stands and interstand tensions as controlled outputs. It is shown that cold rolling process can be described by a nominal model perturbed by an additive uncertainty. This model is used to design a robust tracking controller, based on H∞ control theory, to ensure robust stability and performance despite the perturbations. The controller is first designed for a wide class of uncertain time-delay MIMO systems and then applied to a typical cold rolling mill. The main contributions of the proposed method are (i) overcoming the interaction between tension stabilization and thickness control, (ii) considering time-delay caused by measurements, (iii) guaranteeing robustness against model uncertainties and external disturbances. The performance of the method is also demonstrated and discussed by various simulations. © KSPE and Springer 2011.
Applied Mechanics and Materials (discontinued) (16627482) 26pp. 1237-1241
Piezoelectric materials are used in various applications as active vibration control, fault detection in structures and piezoelectric accelerators, therefore, analysis of such materials seems to be necessary in modern mechanical constructions. In this paper, the dynamic analysis of the beam equipped with piezoelectric patches, used as both sensor and actuator, is presented and the beam deflection due to external inputs (force or voltage) is analyzed via modal analysis method. Then, constructing a model for the flexible beam, by the assumed mode approach, an active vibration control is developed by optimal positioning of piezoelectric patches. Simulation results are also presented to illustrate the effectiveness of the methods proposed for dynamic analysis and active vibration control. © (2010) Trans Tech Publications.
Nonlinear Dynamics (0924090X) 59(3)pp. 477-483
The problem of synchronizing a unified chaotic system in the presence of parameter variations, unstructured uncertainties, and external disturbances is addressed. To tackle such perturbations whose bounds may be unknown, two robust adaptive algorithms are proposed. The stability analysis is presented based on the Lyapunov stability theorem. Simulation results demonstrate the performance of the developed synchronization schemes. © 2009 Springer Science+Business Media B.V.
Nonlinear Dynamics (0924090X) 56(1-2)pp. 13-22
This paper addresses the robust tracking control problem for a class of uncertain nonlinear systems with time-varying parameters, perturbed by external disturbances. The unknown time-varying parameters and disturbances are neither required to be periodic nor to have known bounds. Depending on the characteristics of disturbance signals, two adaptive-based control algorithms are developed. First, an adaptive H ∞ control is designed that achieves: (i) an H ∞ tracking performance when the external disturbances are L 2 signals, and (ii) the convergence of tracking error to zero if the disturbances are bounded and L 2 signals. Then a novel adaptive control algorithm is proposed, only with the assumption of boundedness of disturbances, to drive the tracking error to zero. The designed tracking controllers are then used for controlling a cart-pendulum system, as an underactuated mechanical system, and chaos synchronization of uncertain Genesio-Tesi chaotic system. Numerical simulations are also given to demonstrate the effectiveness of the proposed control schemes. © 2008 Springer Science+Business Media B.V.
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences (17451337) 91(9)pp. 2507-2513
The problem of designing a robust adaptive control for nonlinear systems with uncertain time-varying parameters is addressed. The upper bound of uncertain parameters, considered even in control coefficients, are not required to be known. An adaptive tracking controller is presented and, using the Lyapunov theory, the closed-loop stability and tracking error convergence is shown. In order to improve the performance of the method, a robust mechanism is incorporated into the adaptive controller yielding a robust adaptive algorithm. The proposed controller guarantees the boundedness of all closed-loop signals and robust convergence of tracking error in spite of time-varying parameter uncertainties with unknown bounds. The parametric uncertain systems under consideration describes a wide class of nonlinear circuits and systems. As an application, a novel parametric model is derived for nonlinear Chua's circuit and then, the proposed method is used for its control. The effectiveness of the method is demonstrated by some simulation results. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.
A robust adaptation algorithm based on error normalization is introduced to update the weights of model reference neural network controller. Tracking error is normalized by a variable normalizing gain specified by solving a constrained optimization problem. The so-called piecewise quadratic cost function is proposed as the performance index to improve the transient response specifications. The conditions for robust convergence, saturation limit of actuators and maximum possible speed of response form the constraints of the problem in terms of the variable normalizing gain. Simulation results provided, demonstrate the improvements in transient behavior of control signal and output response obtained by the method, even in the presence of disturbances and parameter variations. ©2007 IEEE.
Parameter adjustment mechanism has an important role to obtain the smooth and fast responses in adaptive control systems. Using the normalized estimation error can improve the robustness properties of the adaptive system despite the perturbations, whereas by which the admissible tracking error and fast convergence may not be obtained necessarily. This paper concerns with the design of a parameter adjustment mechanism ensures that robust, fast and smooth convergence is obtained despite the disturbances and parameter variations. The algorithm is developed based on a variable normalizing gain to guarantee the convergence and then improved by combining with an unnormalized estimation approach to meet all the desired specifications. The proposed algorithm is then applied to Model Reference Adaptive Control (MRAC) scheme to ensure that robust tracking is obtained despite the perturbations. Simulation results show the capability of the proposed algorithm compared to the pure normalized or unnormalized approaches. © 2007 IEEE.
