Sharif Digital Repository

Ignoring actuator dynamics in control of rigid manipulators can in practice result in performance degradation or loss of system stability. However, on the other hand, consideration of actuator dynamics usually requires measurement of robot joint torques that is not cost-effective. This thesis addresses motion tracking control of an n-DOF rigid robot by taking into account its actuator dynamics. Joint torque measurement is avoided by using an adaptive observer. The novelty of this thesis is in developing a controller for robot manipulators including non-negligible actuator dynamics in presence of uncertainty in robot dynamics; without using joint torque measurement. Controller design is done... 

In this thesis, a bioreactor with oscillatory and chaotic behavior has been studied and a control method has been proposed. This bioreactor shows oscillations for some special values of its parameters. The system dynamic is chaotic when a forced perturbation on the feed concentration is imposed. Dynamic behavior of this oscillatory and chaotic reactor has been illustrated. The main objective is control of product concentration. To do this, first system control is considered by proposing several control strategies for SISO case, then system in MIMO case is studied for achieving a globally controllable system. In SISO case, the performances of controllers are compared based on an objective... 

In this project roll channel autopilot of an agile flight vehicle has been studied. In skid-to-turn tactical flight vehicles according to the type of control strategy, for achievment of acceleration commands, the roll angular velocity should be kept near zero. In usual autopilot design, effects of channels on each others is ignored. But three channels of agile flight vehicles have some mutual effects, that consists of kinematic, inertial and aerodynamic couplings. In the case of roll channel dynamics, aerodynamic couplings are dominant and apears because of two factors: roll induced moment and roll cross coupling moment.
After study and aerodynamic modeling of mentioned factors, based... 

Hybrid systems are the systems that in addition to their dependency on time, the occurrence of variouis events paly a vital role in their dynamic behavior. These systems inherit the characteristics of two inherently different categories of the dynamic systems which are: a) the continuous-variable dynamic systems; and b) discrete-event systems. Many systems in science and engineering can be considered as hybrid systems; among these one can mention the dynamic operation of stage wise processes, in which each mode of operation has its own dynamic behavior. Transition from one mode to another one is caused by the occurrence of various events. The main objective of this work is to investigate... 

In recent decades, the study of Nano and Micro Electromechanical Systems (NEMS and MEMS) as in micro sensors and actuators or in Atomic Force Microscopes (AFM) attracted considerable attention. Since an indispensable part of such systems is a nano or micro flexible beam, the inevitable undesirable vibrations of the flexible beam necessitate the implementation of vibration control strategies. Recently, some cutting edge experiments on statics and dynamics behavior of micro beams have been conducted that reveal some deviations from the prediction of classical theories, and hence this leads to development of strain gradient elasticity theory. In addition, the often-adopted finite dimensional... 

In this thesis, the performance of a special type of controllers, called Proportional-Integral weighted (PIw) controllers, in control of nonlinear systems is studied. To this aim, the domain of attraction of polynomial nonlinear control systems in the presence of PIw and Proportional-Integral (PI) controllers is estimated and compared with each other. For this estimation, two different methods are used, and the obtained results are compared. Next, adaptive PIw and adaptive PI controllers are designed to be used in control of nonlinear systems. The effectiveness of the proposed controllers is illustrated for a Continuous-Stirred-Tank-Reactor (CSTR) that has an uncertain parameter in its... 

The purpose of this paper is to design an integrated controller and observer (ICO) for a nonlinear system using genetic programming. ICO is a function that constructs control command directly from the measured state variables of the system. It means that, this function should imitate the behavior of the observer and controller and control the system with acceptable performance in different initial conditions, at the presence of disturbances and system uncertainties. The complexity of this design method, is not related to the complexity of the plant, in fact, the complexity in plant just effects at run time, but the design procedure does not change. So, if exact model of plant exist, using... 

In this study, an adaptive controller design for nonlinear fractional order systems in the strict-feedback form has been investigated. The system is subject to unknown dynamics, unmeasured state variables, quantized input and output, and input nonlinearity. A linear observer is used to solve the problem of unmeasured state variables. The fuzzy logic system is used to estimate the unknown functions, and instead of updating all the regressor weights, only the upper bound of their norms is updated, which significantly reduces the computational load. In the controller design, limitations due to the bandwidth of data transmission have been considered by applying quantizers in the input and output... 

Identifying fractional systems and designing controllers for these systems is one of the leading challenges due to their limitations. Systems can have constraints on output, input, and states. These constraints make it difficult to design a controller. In this project, controller design methods for fractional-order systems with output constraints are investigated. A controller is designed for a strict feedback nonlinear system with unknown dynamics subject to asymmetric and variable output constraints, unknown direction of the controller, and unmeasurable states. To design the controller, the direct and backstepping technique is used and the Lyapunov barrier function is applied for the first... 

Switched systems as a subset of hybrid systems have both discrete and continuous behaviors and have attracted a lot of attention during the past decades. A set of subsystems or modes whose sequence is specified by a switching rule makes the switched system. Another category of systems is the fractional order system in which the order of derivatives is not limited to integers. This feature has provided a significant capacity for this type of system. On the other hand, every real system faces a set of limitations that neglecting them may reduce the quality of control or even lead to system instability. The purpose of this research is to model and control the switched system, whose subsystems... 

The objective of this research is designing a controller for the event-triggered control of multi-agent systems in the presence of common constraints. In this regard, an adaptive decentralized event-driven controller is designed for the agents of a multi-agent system. The dynamics of the agents are nonlinear and unknown and they are subject to external disturbances. This controller is capable of achieving the objective of consensus with the desired performance in the presence of sensor and actuator faults, input nonlinearity, input and output quantization, and unmeasured states. The stability of the closed-loop system has been established via Lyapuonov theory. The considered multi-agent...