Sharif Digital Repository

Polyethylene terephthalate (PET) is known as the most important polyester in the world. This polymer is the raw material for synthetic fibers, films and plastic objects and widely used in textiles and food industry. In this project transesterification and polycondensation reactors of a semi-batch process with dimethyl terephthalate/ethylene glycol feedare simulated. First simulations areperformed for reactors in the laboratory scale.Then the reactors are scaled up to industrial scale in order to produce 100 tons per year of PET product. The optimal temperature trajectory for the fisrt reactor is obtained based on a performance index. This performance index includes the reaction time and... 

The purpose of this study is to propose a stable treatment strategy for hepatitis C infection by considering several practical limitations of the treatment and using control theories. First, hepatitis C disease and its transmission, diagnosis, and treatment methods have been introduced. Then, the mathematical models of hepatitis C dynamics in the body have been presented, and their ability in predicting the observed clinical behaviors of the patients has been studied. Thereafter, the extended versions of these models by considering pharmacokinetics/dynamics equations of the drugs have been proposed to have a more realistic mathematical model. After that, the practical features of the disease... 

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... 

In this thesis, simulation and control of intracranial pressure and temperature has been studied. Common methods for control of intracranial pressure and temperature are hypothermia treatment and drug therapy. Hypothermia is a clinical treatment for cooling the patient body with cold water-circulating blanket to decompress intracranial pressure by decreasing body temperature. In order to simulate the patient body, two mathematical models for single-input single-output and multi-input multi-output systems that are proposed in the literature are chosen. The thermodynamic- hemodynamic model was simulated as single-input single-output system and the thermodynamic- hemodynamic- pharmacokinetic... 

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... 

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... 

The purpose of this thesis is design of an adaptive tracking control for input-quantized strict-feedback fractional order nonlinear systems with unknown dynamics and asymmetric time-varying output constraints. The controller design is achieved by using a hysteretic quantizer to avoid chattering and not needing the quantization parameters. The fuzzy logic method has been used to solve the problem of unknown dynamics. Also, due to the asymmetric time-varying output constraints, the Barrier Lyapunov function has been used. In this thesis, less restrictive assumptions have been considered than the work performed in previous researches.By utilizing the adaptive backstepping approach and based on... 

Final control elements usually have nonlinear dynamics which affect the stability of the closed- loop system. Four most common types of these nonlinearities are dead-zone, backlash, hysteresis and saturation. Because most of final control elements especially in chemical processes are subjected to saturation constraint and also due to lack of generaland practical control scheme to handle this limitation, our concentration will be focused on saturation nonlinearity. In this work, based on sliding mode control strategy, a control scheme for multi-input multi-state systems in the presence of input saturation is presented. Some numerical simulations are carried out to show the effectiveness of... 

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... 

Biotechnology is one of the fields that has had great advances in the past decades, and therefore controlling biological processes (bioreactors) is considered as an important issue. The purpose of current thesis is designing an adaptive controller for a bioreactor by considering input constrain and proving the stability of closed loop. A standard bioreactor has been chosen for this purpose. First a non-adaptive controller has been designed. Then an adaptive controller is designed and implemented on a bioreactor in the presence of input constraint, because in practice the system parameters are unknown. Finally by applying disturbance to the system, it has been shown that the proposed control... 

This work addresses adaptive neural control for a class of stochastic nonlinear systems in the nonstrict-feedback form. By introducing a nonlinear mapping, the output-constrained stochastic system transformed into a new system without constraint. The systems under study is subject to state time delay, input nonlinearity, unavailable states, unknown dynamics and actuator failure. The appropriate Lyapunov-Krasovskii functionals is used to compensate the time-delay effects, the neural network is used to approximate the unknown nonlinearities, the linear state observer is constructed to estimate the unmeasured states, and a variable separation method is used to deal with the difficulty caused by... 

Most of dynamical models in the real world, have various restrictions and complexities in their structures. These constraints make the controller design much more difficult. In this work, it has been tried to design the controller for two kinds of common dynamical systems in the presence of these restriction by using the fuzzy logic systems. Several restrictions are investigated in this project such as unknown dynamic of the model, unmeasured state variables, unknown control directions, existence of time delay in the input and the state variables, input saturation and controller singularity.The backstepping technique and the dynamic surfaces control approach have been used to design the... 

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... 

In this work steady state and dynamic performances of quaternary distillation column sequences designed based on steady state and dynamic cost functions have been investigated. To quantify the dynamic performance, product loss due to disturbances has been considered in the objective function. In addition, variations of operating costs such as utilities have been considered in the objective function. To separate a quaternary mixture into four products, twenty two configurations have been used. It has been observed that the feed composition, disturbance frequency and magnitude affect the dynamic behavior strongly. To decrease the optimization computational load, a scheme that provides a... 

In this research work, mixed convection heat transfer of ferrofluids (i.e., magnetite nanoparticle) in a circular pipe fully filled with a porous medium in the presence of constant and alternating magnetic fields has been investigated both numerically and experimentally. The duct was heated by a heating coil and the magnetic field was applied via four electromagnets with U shaped ferrite cores and a frequency inverter. The nanoparticles were synthesized using co-precipitation method and coated with a surfactant (i.e., Tween 80) and doubled distilled water was used as the base fluid. To characterize the synthesized nanoparticles, various analyzing techniques such as VSM, SEM, and XRD were... 

The PID controller has been widely used in the industry for many years because of its simple structure and satisfactory performance. If the process is time-varying or has a nonlinear dynamic, the PID controller with constant parameters can not control the process in a wide range of operation and adaptive PID controller should be used. In this thesis, two adaptive controllers proposed in the literature, one for multi-input multi-output (MIMO) affine nonlinear systems and another for single-input single-output (SISO) non-affine nonlinear systems both in the normal form that both of them are extended in to the general form. The latter extended controller includes the MIMO systems. The main... 

Due to advances of biotechnology, control of bioprocess has become very important. The goal of this project is to simulate the acetic acid production bioreactor and designing an adaptive PI controller for this reactor. For this goal, a suitable model has been selected from the literature and simulation has shown that the system has a nonlinear dynamical behavior. In order to control the system in a wide range of operating conditions, the adaptive PI controller was designed. In single input-single output case, the concentration of the product is controlled in such a way that the production rate is maximized, assuming that the pH and temperature are kept constant. Then a two input-two... 

Because of lower energy consumption and lower capital cost, divided wall columns attracted wide attention. The main challenge of these units is their controllability. In this thesis dynamic simulation and control of a divided wall column is investigated and an adaptive model predictive controller has been used for control purpose. For dynamic simulation the Aspen Dynamics software and for applying control strategy the MATLAB software have been utilized. The model used for model predictive controller has been obtained by using open loop responses of the system. The main advantage of presented work over the existing ones is using the input-output transfer function of the system model instead... 

The accurate fault diagnosing system design helps the process safety and also helps increasing the products quality of the process. In this project, the fuzzy system and neural network have been used for fault detection and diagnosis of a yeast fermentation bioreactor. In one case, parameters of membership functions are selected in a conventional manner. In second case, the optimal values of these parameters have been obtained using the genetic algorithm. In another case, the neural network system is used for fault detection. These three cases are compared based on their performances in fault diagnosis of a yeast fermentation bioreactor for three different conditions. The results indicate...