Sharif Digital Repository

In this paper based on the sliding mode concept, a nonlinear delayed feedback control is proposed for stabilizing the unstable periodic orbits (UPOs) of chaotic systems. It is assumed that the period of the desired UPO is known, but its time series and the initial conditions generated the UPO are not available. The ability of the proposed control method in stabilizing the UPO of the chaotic systems is analytically proved and the effectiveness of the method is numerically examined by applying it to the chaotic Duffing system. © 2007 Elsevier Ltd. All rights reserved  

This paper is concerned with the stability of nonlinear Lipschitz systems subject to bounded process and measurement noises when transmission from sensor to controller is subject to distortion due to quantization. A stabilizing technique and a sufficient condition relating transmission rate to Lipschitz coefficients are presented for almost sure asymptotic bounded stability of nonlinear uncertain Lipschitz systems. In the absence of process and measurement noises, it is shown that the proposed stabilizing technique results in almost sure asymptotic stability. Computer simulations illustrate the satisfactory performance of the proposed technique for almost sure asymptotic bounded stability... 

Bounded-input bounded-output (BIBO) stability of distributed-order linear time-invariant (LTI) systems with uncertain order weight functions and uncertain dynamic matrices is investigated in this paper. The order weight function in these uncertain systems is assumed to be totally unknown lying between two known positive bounds. First, some properties of stability boundaries of fractional distributed-order systems with respect to location of eigenvalues of dynamic matrix are proved. Then, on the basis of these properties, it is shown that the stability boundary of distributed-order systems with the aforementioned uncertain order weight functions is located in a certain region on the complex... 

This paper addresses design of an adaptive fuzzy decentralized fault-tolerant controller for a class of uncertain multi-input multi-output (MIMO) large-scale nonlinear systems with unmodeled dynamics subject to unknown state time-varying delay, external disturbances, unknown input saturation and actuator faults. It is shown that the proposed fault-tolerant control (FTC) scheme can handle infinite number of actuator failures including partial and total loss of effectiveness. System uncertainties have been approximated by the fuzzy logic systems (FLSs). To cope with the unknown state time-varying delay, the Razumikhin lemma has been utilized and unmodeled dynamics has been tackled by... 

Optimal control of large-scale uncertain dynamic systems with time delays in states is considered in this paper. For this purpose, a two-level strategy is proposed to decompose the large-scale system into several interconnected subsystems at the first level. Then optimal control inputs are obtained by minimization of convex performance indices in presence of uncertainties, in the form of states and interactions feedback. The solution is achieved by bounded data uncertainty problems, where the uncertainties are only needed to be bounded and it is not required to satisfy the so-called 'matching conditions'. At the second level, a simple substitution-type interaction prediction method is used... 

This paper presents a modified sensor-based online method for mobile robot navigation generating paths in dynamic environments. The core of the navigation algorithm is based on the velocity obstacle avoidance method and the guidance-based tracking algorithm. A fuzzy decision maker is designed to combine the two mentioned algorithms intelligently. Hence the robot will be able to decide intelligently in various situations when facing the moving obstacles and moving target. A noble noise cancellation algorithm using Neural Network is designed to navigate the robot in an uncertain dynamic environment safely. The results show that the robot can track a moving target while maneuvering safely in... 

Most existing methods for satellite attitude control assume that full knowledge of satellite attitude is available by algebraic manipulation of at least two vector measurements from attitude sensors such as Sun, Earth-horizon, Earth-magnetic or star tracker sensors. Kalman filtering is usually used when only one vector measurement is available, however, asymptotic stability of nonlinear and uncertain dynamics of satellite is not guaranteed in this case. This technical note presents a coupled nonlinear estimator-controller for satellite attitude determination and control by using a 3-axis gyro and a single vector measurement for a fully actuated satellite. We assume that the moment-of-inertia... 

We present a method for global estimation of joint velocities in robot manipulators. A non-minimal model of a robotic manipulator is used to design an adaptive observer capable of handling uncertainties in robot dynamics. Dimension of the proposed observer is shown to be at least 3n where n stands for the manipulator degrees of freedom. This number is less than the dimension of most of existing globally convergent adaptive observers. Global asymptotic convergence of system state estimates to their true values is achieved under no persistency of excitation condition. Smoothness of the dynamics of the proposed observer allows its easy implementation in comparison with non-smooth observers....