Sharif Digital Repository

Fault occurrence is an inevitable problem in industrial plants. These faults have numerous types. Some common kinds of faults are faults in actuators, faults in system dynamics, and faults in sensors. In many cases it is not possible to change or repair the broken part immediately. On the other hand, it is not reasonable to shut-down the whole system due to a minor failure. Therefore we should take a measure to have the best output possible in a faulty plant. In this thesis we have proposed a new static compensator by which we distribute the contribution of the faulty actuator among the other ones. At the end we evaluate the method by means of simulations  

Considering input constraints is an essential task in the controller design. In this thesis, a controller has been designed for incommensurate fractional order nonlinear systems in the nonstrict feedback form subject to unknown dynamics, input nonlinearity and actuator failures. The Lyapunov direct method and the backstepping technique have been used to design the controller and stability analysis. The number of actuator faults can be infinite. In addition, the proposed control algorithm can cope with different types of input nonlinearities namely, saturation, dead zone, dead zone-saturation, backlash and hysteresis. To estimate the system uncertainties, neural networks have been employed... 

The objective of this research is to design an adaptive controller for a class of fractional-order nonlinear systems in the strict-feedback form with unmodeled dynamics. Actuator saturation and actuator fault are also considered. All of the system states are assumed to be measurable, and all the sensors can be faulty. Fractional-order systems are chosen because, in the modeling of physical systems, the fractional-order calculus is often preferable to the classical integer-order calculus. The controller is designed by using the backstepping design technique. The fuzzy logic systems are used to eliminate the problem of "explosion of complexity" in the conventional backstepping method and also... 

This thesis deals with output feedback control design, adaptive output feedback control design, and adaptive actuator compensation for input-affine nonlinear systems on the basis of contraction metrics. In Section I, some necessary backgrounds on Riemannian geometry and contraction analysis are presented. In Section II, firstly, an observer for the considered class of nonlinear systems is proposed. Then, it is shown that by combining the introduced observer with state-feedback controllers in a suitable way, output tracking can be achieved. Moreover, the obtained results are extended to be used for adaptive output feedback stabilization of uncertain nonlinear systems. The introduced... 

Due to the presence of a random variable in the process dynamics or due to the presence of measurement noise, many processes have stochastic in nature. Behaviors of these processes are different from the deterministic processes and therefore their controllers are also different. The aim of this research is to design adaptive controller for stochastic processes with a non-strict feedback structure and in the presence of input constraints. Also, the considered system has other limitations such as the unmeasured states, actuator failure, unknown dynamics and fixed time stability is desired. The input limitation can be caused by the limitation of the final control element, because the input... 

In control systems, actuators are subjected to faults during operation. In the present work, a controller for nonlinear systems under several restrictions and in the presence of actuator failure has been proposed. The controller is designed for large-scale multi-input multi-output (MIMO) uncertain nonlinear systems subject to unmodeled dynamics, unknown state dependent control gain functions, unknown state time varying delay, unknown subsystems interactions, unknown external disturbances and input nonlinearity. The backlash has been assumed for input nonlinearity. No restriction has been considered regarding the number of actuator failure. The backstepping technique has been applied for...