Sharif Digital Repository

In this work, design of an observer-based nonlinear controller for a class of single input-single output (SISO) systems in the general strict feedback form subject to input saturation based on the back-stepping technique has been addressed. A full order adaptive observer is constructed to estimate the unknown states and system parameters simultaneously. The proposed control scheme is singularity free and can handle the input nonlinearity. Asymptotical stability of the closed-loop system in the presence of observer dynamics and input saturation has been established by the Lyapunov stability theorem. The effectiveness of the proposed controller is illustrated by applying the proposed scheme to... 

In this paper, an approach is proposed for controlling the uncertain Lorenz system. Based on an identification technique, a controller is designed that guarantees the regulation of all states in the presence of system uncertainty. Since in some applications the challenging problem of output tracking is desired, we have proposed several effective set-point tracking control techniques. The control schemes that are based on the feedback linearization method, can stabilize the internal dynamics of the system. Simulation results have illustrated the effectiveness of the proposed schemes. © 2005 Elsevier Ltd. All rights reserved  

The forecast errors for distributed energy resources (DERs) and hourly demands have contributed to power system uncertainties and additional risks in the day-ahead scheduling of electricity markets. In this paper, a risk-based approach is introduced to determine the stochastic solution of network-constrained unit commitment (NCUC) when additional uncertainties are embedded in the power system scheduling. The historical power market transaction data are used to model nodal injection uncertainties and reserve capacity requirements are considered to assess the solution of the risk-based NCUC. The proposed NCUC problem is formulated as a single-stage second order cone program which is a convex... 

Hastening the power industry reregulation juxtaposed with the unprecedented utilization of uncertain renewable energies (REs), faces power system operation with sever uncertainties. Consequently, uncertainty assessment of system performance is an obligation. This paper reviews the probabilistic techniques used for probabilistic optimal power flow (P-OPF) studies and proposes a novel and powerful approach using the unscented transformation (UT) method. The heart of the proposed method lies in how to produce the sampling points. Appropriate sampling points are chosen to perform the P-OPF with a high degree of accuracy and less computational burden compared with features of other existing... 

Despite significant advancements in medicine, human blood is still a scarce resource. Only humans produce it, and there is currently no other product or alternative chemical process that can be used to generate blood. For this reason, blood is a vital commodity in healthcare systems. Since blood is also a perishable product, its inventory management is difficult. The challenge is in holding enough stock to ensure a high level of supply while keeping losses from expiration at a minimum. This research will investigate blood inventory management in a hospital, and develop a mathematical model to manage blood ordering and issuing. This study will account for the fact that blood demand and supply... 

Development of design and production technology of centrifugal pumps for achieving better performance and less energy consumption in these devices has increasingly been taken into consideration. This is due to the fact that centrifugal pumps have an important contribution in industrial applications and energy consumption around the world. Accordingly, the international standards of centrifugal pumps, urge more precise analysis systems for obtaining the performance curves of these pumps. For this reason, a complete, precise and real-time monitoring and performance analysis system for centrifugal pumps is introduced in this paper. The pump characteristics are measured by precise measuring... 

In this Letter, we propose a fractional-order controller to stabilize the unstable fixed points of an unstable open-loop system. Also, we show that this controller has strong ability to eliminate chaotic oscillations or reduce them to regular oscillations in the chaotic systems. This controller has simple structure and is designed very easily. To determine the control parameters, one needs only a little knowledge about the plant and therefore, the proposed controller is a suitable choice in the control of uncertain chaotic systems. © 2007 Elsevier B.V. All rights reserved  

Coordinated operation of hydro-thermal power systems helps reduce generation costs. The Hydro-Thermal Coordinating Model (HTCOM) software package, as one of these models, determines long-term operational policies for a hydro-thermal power system with multipurpose reservoirs. The CLT was incorporated within this framework to ensure a logical time-based run-time, with no serious decrease in precision. HTCOM, based on both its theoretical background and its application in the KWPA system, has shown that it can handle real world problems successfully, with more reliable outcomes. Many models have also been developed to optimize the planning of hydro-thermal systems. HTCOM was developed and... 

Active disturbance rejection control (ADRC) is applied to a one-axis gimbal mechanism. The dynamic model of the system is derived and validated from mathematical modeling and practical experiments. Disturbances acting on the complete model of the gimbal mechanism are introduced via base lateral acceleration and angular motion. The ADRC is designed by utilizing an extended state observer for observing and suppressing the effects of external disturbances and internal parameter uncertainties. A PID controller is used to form a basis of comparison for set-point tracking and disturbance rejection performance. The effects of identification errors and observer bandwidth are experimentally... 

Active disturbance rejection control (ADRC) is applied to a one-axis gimbal mechanism. The dynamic model of the system is derived and validated from mathematical modeling and practical experiments. Disturbances acting on the complete model of the gimbal mechanism are introduced via base lateral acceleration and angular motion. The ADRC is designed by utilizing an extended state observer for observing and suppressing the effects of external disturbances and internal parameter uncertainties. A PID controller is used to form a basis of comparison for set-point tracking and disturbance rejection performance. The effects of identification errors and observer bandwidth are experimentally... 

This paper proposes event-triggered rules for stabilizing the equilibrium point of a class of nonlinear systems, on the basis of indefinite Lyapunov theory. Unlike the traditional event-triggered control methods, which have been constructed based on the Lyapunov theory, the timederivative of the corresponding Lyapunov function can be positive in some time periods by using the proposed eventtriggered rules. For a class of uncertain nonlinear systems with matched uncertainty, the proposed event-triggered controller guarantees that the trajectories of the system tend to an arbitrary small neighborhood of the equilibrium point of the system. Numerical examples confirm the obtained analytical... 

This paper presents a new method to simultaneously optimize components' size, set points of the control system and slope of PV panels of standalone hybrid energy systems (HESs) using the Passive Congregation PSO (PSOPC) approach. New control set points are defined for the HES, and a new operation strategy is presented based on the defined set points. The optimization algorithm determines the optimal values of the set points to efficiently optimize the HES operation. The effectiveness of the proposed control set points is finally verified through some numerical analyses. In this regard, the proposed optimization method is employed to optimize various HES configurations and compared with other... 

This paper presents a new method to simultaneously optimize components' size, set points of the control system and slope of PV panels of standalone hybrid energy systems (HESs) using the Passive Congregation PSO (PSOPC) approach. New control set points are defined for the HES, and a new operation strategy is presented based on the defined set points. The optimization algorithm determines the optimal values of the set points to efficiently optimize the HES operation. The effectiveness of the proposed control set points is finally verified through some numerical analyses. In this regard, the proposed optimization method is employed to optimize various HES configurations and compared with other... 

There are different choices for auction and settlement mechanisms in electricity markets; however, selecting the appropriate mechanisms is too hard. Traditionally, the offer cost minimization (OCM) mechanism that minimizes the total offer cost is used as the clearing mechanism, and payments are calculated based on locational marginal prices (LMPs). Under this setup, the clearing and settlement mechanisms are inconsistent, since the minimized cost is different from the total payment cost. Some recent studies have proposed the payment cost minimization (PCM) mechanism. However, the discussion is still open, and different aspects of these mechanisms are yet needed to be analyzed. This paper... 

Robust performance controller design for duty-cycle controlled series resonant converter is proposed in this paper. The uncertainties of the converter are analyzed with load variation and power circuit components tolerances are taken into consideration. Additionally, a nominal performance H ∞ controller is designed. Closed-loop system is simulated and simulation results of robust controller are compared with H∞ nominal performance controller  

Deregulation in power systems has created new uncertainties and increased the previous ones. The presence of these uncertainties causes the transmission network to remain monopoly and the private investors not being interested in investing in this section. This paper presents a new merchant-based transmission expansion planning (TEP) formulation from the viewpoint of private investors. The information-gap decision theory (IGDT) is used to model the inherent uncertainties associated with the estimated investment cost of candidate lines and the forecasted system load and NSGAII is utilized to solve the multi-objective optimization problem. This algorithm helps private investors to select the... 

We study the rotational motion of nano-flake ferromagnetic disks suspended in a Newtonian fluid, as a potential material owing the vortex-like magnetic configuration. Using analytical expressions for hydrodynamic, magnetic and Brownian torques, the stochastic angular momentum equation is determined in the dilute limit conditions under applied magnetic field. Results are compared against experimental ones and excellent agreement is observed. We also estimate the uncertainty in the orientation of the disks due to the Brownian torque when an external magnetic field aligns them. Interestingly, this uncertainty is roughly proportional to the ratio of thermal energy of fluid to the magnetic energy... 

This work presents a new necessary and sufficient condition for robust stability and robust performance of positive linear time invariant (LTI) systems with structured uncertainties. It is known that robustness analysis of LTI systems with structured uncertainties requires evaluation of structured singular value (SSV), which is known to be NP-hard. This paper shows that for positive systems, the structured singular value can be estimated efficiently using linear programming. Thus, the robustness analysis of positive systems is simplified to easily verifiable conditions that scale linearly with the dimensions of the system. This property finds great utility in analysis and synthesis of large...