Sharif Digital Repository

We study a system of ordinary differential equations which describes the metapopulation SIR model. The main target is to control the epidemic spreading using the structure of connections between cities. For this purpose, we formulate optimal control strategy that the control represents a drug treatment and Prevention strategies . Some methods are given in numerical example section such as control through spectral radius of movement matrix or optimal control through travelling between cities. Existence results for the optimal control are studied  

This study deals with a generalised version of lead/lag compensators known as fractional-order lead/lag compensators. Exact and simple formulas are found for designing this introduced type of fractional-order compensators in order to provide the required magnitude and phase at a given frequency. Also, the region in the phase-magnitude plane, which is accessible by these compensators, is analytically found. Moreover, numerical examples and experimental results are presented to show the applicability of the achievements of this study in control system design  

In most existing works on the flocking problem, results were obtained for the case where a double integrator dynamic is used to describe motion of agents and virtual leader. These results, however, may not be generalised to agents with general linear dynamic. In this study, it is shown that in the flocking of agents with a linear dynamic, the velocity convergence of agents does not generally lead to the position convergence of informed agents and the position convergence is possible only for a specified group of linear dynamics. In this study, a control protocol is proposed to flock agents with specified linear dynamics and guarantee the velocity convergence of all agents as well as average... 

A new methodology has been proposed to model and predict the pilot rating of a typical aircraft for flights through turbulences. The main idea here is to correlate the so-called "pilot rating" to the pilot physical energy demanded by the aircraft in a given flight condition and flying task. The proposed methodology, in addition to the other known factors, accepts the level of the human pilot physical energy consumed in each suitable period of time as well as the rate of energy consumption in the same period. These two, form the prime factors to predict the pilot rating in flying tasks that have a reasonable duration. Different case studies conducted by the authors show that for cases like... 

The controllable flaps and interceptors in planing crafts not only may reduce the resistance, but also could be designed to make a boat run at or near optimum attitude in various environments, which results in a reduction in both resistance and vertical motion in waves. Planing vessels suffer from porpoising instability and violent vertical motion at high forward speeds. The controllable flaps and interceptors can be used to control and reduce the vertical motion of planing crafts. In the present study, the impact of controlled interceptors on a planing craft seakeeping quality is investigated through application of experimental and theoretical methods. In the experimental part of the study,... 

In this paper, a novel robust adaptive control method is proposed for controlling the Lorenz chaotic attractor. A new backstepping controller for the Lorenz system based on the Lyapunov stability theorem is proposed to overcome the singularity problem that appeared in using the typical backstepping control method. By exploiting the property of the system, the resulting controller is shown to be singularity free and the closed loop system is globally stable. Due to unavailability of system states measurement in practice, the controller is selected such that only one system state is needed. To overcome the problem of parameter uncertainty, an additional term to Lyapunov function is added and... 

In this study, an accurate analytical solution for Duffing equations with cubic and quintic nonlinearities is obtained using the Homotopy Analysis Method (HAM) and Homotopy Pade technique. Novel and accurate analytical solutions for the frequency and displacement are derived. Comparison between the obtained results and numerical solutions shows that only the first order approximation of the Homotopy Pade technique leads to accurate solution with a maximum relative error less than 0.4%. © 2008 Elsevier Ltd. All rights reserved  

In this paper, a new approach for path generation and control of multi-agent systems is proposed. This method is based on global optimization techniques used for solving the inverse kinematic problem of redundant manipulators. Convergence of any performance function such as obstacle avoidance, collision avoidance, and heading angle to its global optimum is guaranteed by introducing a control law which is based on the Pontryagin's Maximum Principle. The efficacy of the proposed algorithm is demonstrated through simulation experiments. © 2006 IEEE  

Most multivariate quality control procedures evaluate the in-control or out-of-control condition based upon an overall statistic, like Hotelling's T2. Although T2 is optimal for finding a general shift in mean vectors, it is not optimal for shifts that occur for some subset of variables. This introduces a persistent problem in multivariate control charts, namely the interpretation of a signal that often discourages practitioners in applying them. In this paper, we propose an artificial neural network based model to diagnose faults in out-of-control conditions and to help identify aberrant variables when Shewhart-type multivariate control charts based on Hotelling's T2 are used. The results... 

This paper studies a brachiation robot that is a long armed locomotion similar to apes. The robot has 2 revolute joints but only one of them is actuated. In this paper, after deriving dynamic model of the robot the Controlled Lagrangian (CL) method is used for stabilization. The matching conditions satisfied for the controller are derived and the extended λ-method is used to solve PDE's involved in the method of controlled lagrangian. Satisfactory controller's gains are chosen by PSO algorithm. Finally, feasibility of the developed controller is investigated by numerical simulations  

This study presents new sufficient conditions for Hurwitz and Schur stability of interval matrices. Tight bounds for the spectrum of interval matrices are estimated using computationally simple optimisation problems. The conservativeness is reduced further by application of ordinary similarity transformation. A necessary and sufficient vertex based criterion for the stability of a subclass of interval systems in continuous and discrete-time cases is also proposed. This enables the spectra for this class of interval systems to be determined exactly. A selection of various examples adopted from existing literature is used to demonstrate the utility of the proposed criteria  

During the milling process, self-excited vibration or chatter adversely affects tool life, surface quality and productivity rate. In this paper, nonlinear cutting forces of milling process are considered as a function of chip thickness with a complete third order polynomial (instead of the common linear dependency). An optimal control strategy is developed for chatter suppression of the system described through nonlinear delay differential equations. Counterbalance forces exerted by actuators in x and y directions are the control inputs. For optimal control problem, an appropriate performance index is defined such that the regenerative chatter is suppressed while control efforts are... 

A new method of integrated guidance and control for homing missiles with actuator fault against manoeuvring targets is proposed. Model of the integrated guidance and control system in the pitch plane with actuator fault and some uncertainty is developed. A control law using combination of adaptive backstepping and sliding mode approaches is designed to achieve interception in the presence of bounded uncertainties and actuator fault. Simulation results show that new approach has better performance than adaptive backstepping and has good performance in the presence of actuator fault  

In this study a hydractive suspension system is designed for a passenger car. By using a mathematical validated model with eight degrees of freedom for a vehicle which is equipped with hydractive suspension, optimal damping forces derived for suspension system on the base of optimal control theory which uses linear quadratic regulators for improving ride comfort of vehicle and saves vehicles stability at the same time. Existing limitations for applying damping forces and time lag of controlling component are considered. The results are being derived according to a bump excitation and nonlinearity effects of the hydractive suspension components. Simulation results for the hydractive optimal... 

Based on the optimal control theory, the present study proposes a novel approach to derive a cooperative guidance law for two pursuers with an arbitrary-order linear dynamics against one zero-lag evader with random step maneuver. This approach is intended to minimize the mean value of the resultant control effort taken over a set of possible evader maneuvers which is modeled as a step function, the parameters of which are unknown. Since the resultant control effort is the minimum effort among the pursuers, we encounter the nonlinear "min" function in the performance index. By introducing binary parameters, it is changed to a linear function including binary parameters and continuous... 

In this study, adaptive observer-based synchronization of chaotic systems is considered. The master and slaves systems have different dynamics and it is assumed that the master system parameters are unknown while its states are available. First, it is assumed that the slave system parameters are known but its states are not completely available. It is shown that an observer for the slave system can be designed and applied for the purpose of synchronization. Based on a Lyapunov function, an adaptive law for master parameters estimation and a control law for the synchronization goal are extracted. Stability of the entire system including the observer dynamics has been proved. Further, it is... 

The energy of a graph G, denoted by E (G), is defined as the sum of the absolute values of all eigenvalues of G. Let G be a graph of order n and rank (G) be the rank of the adjacency matrix of G. In this paper we characterize all graphs with E (G) = rank (G). Among other results we show that apart from a few families of graphs, E (G) ≥ 2 max (χ (G), n - χ (over(G, -))), where n is the number of vertices of G, over(G, -) and χ (G) are the complement and the chromatic number of G, respectively. Moreover some new lower bounds for E (G) in terms of rank (G) are given. © 2008 Elsevier B.V. All rights reserved