Sharif Digital Repository

Existence of time delay and interactions of control loops make control of multivariable delayed systems more difficult، therefore control of these systems is important. In this project a control scheme based on prediction of process output has been proposed. Traditional PI controllers are used in the control structure and controller parameters are tuned by genetic algorithm. Unlike the Smith predictor based methods، which become internally unstable when applied to unstable plants، unstable delayed multivariable systems can be handled by proposed method. It can also be applied to stochastic systems. The robust version of the control scheme has also been designed. Effectiveness of the proposed... 

In this study the problem of position and attitude control of a Spacecraft has been investigated under position and attitude constraints as well as uncertainties in mass, moments of inertia, thrust vector error, and external disturbances. The Lyapunov theory is utilized for deriving the appropriate controls. Two kinds of controls are derived in the first step. The first kind has been derived using direct Lyapunov method and the second by the use of back-stepping method. Obtained simulation results prove that the first control scheme is more suitable for a Spacecraft control, since it has less computational effort, convenient selection of control parameters, and especially it has less... 

During the turning operation, the interaction of the metal cutting process and machine tool causes a dynamic instability called self-excited vibration or chatter. Limited productivity rate, decrease in tool life, poor surface quality and noisy workplace are some adverse effects of the chatter vibration. Chatter suppression in machining processes results in more material removal rate, high precision and surface quality. In this thesis, two control strategies are developed to suppress chatter vibration in turning process including a worn tool. A single degree of freedom model of the turning process including tool wear is briefly described. In the first stage, a sinusoidal spindle speed... 

Best cancer treatment is the one which reduces the tumor density in minimum time and side effects, considering the input limitations. In this paper, tracking controller and robust controllers are designed to achieve the mentioned objectives, simultaneously. An ODE-based mathematical model of the human body under chemovirotherapy is selected, which includes the uninfected and infected tumor cells, free viruses, immune cells, and a chemotherapeutic drug. For tracking purposes, a servo controller based on the entire eigenstructure assignment (EESA) approach is applied to the model, continuously and discretely. For robust purposes H-infinity and D-K iteration approaches are implemented and... 

Today, cancer mortality is one of the most important problems, even considering the scientific advances that offer more effective solutions to treat some diseases, providing a way to prevent and treat this disease is one of the most important issues that engineers have considered. This is achieved by designing a controller to minimize the size of the cancer tumor population, increase healthy cells, optimize treatment time, and drug dose.To achieve this goal, pharmacokinetic, pharmacodynamic, tumor growth, and healthy cell growth models, and mathematical models for subsystems that affect tumor growth, such as the angiogenic system, have been studied to develop a single mathematical model. In... 

Nowadays, modern life needs energy resources. In the last few centuries, countries have focused on the use of fossil fuels. However, excessive use of fossil fuels, such as oil and coal, has resulted in enormous environmental hazards. Global warming and air pollution are the most visible manifestations of these hazards. In recent years, energy researchers have been looking for alternative sources. The result of this approach is to pay attention to clean and renewable resources such as wind energy.Wind turbines are used to generate electrical energy out of wind. Among the different types, floating offshore wind turbines have been mostly considered because of various benefits. However, they... 

New nonlinear voltage and current control strategies based on backstepping control and a high-order sliding mode differentiator for microgrid are proposed. The microgrid consists of multiple distributed generation (DG) units with an arbitrary configuration that can be parametrically uncertain or topologically unknown. The proposed method robustly regulates the microgrid voltages and currents in the presence of parametric uncertainties, unmodeled dynamics, load imbalances, and nonlinear loads with harmonic/interharmonic currents. In contrast to existing methods, the proposed method does not need to know the frequency of harmonic and interharmonic current of microgrid loads that lead to the... 

In this thesis, two-level optimal control of uncertain and non-uncertain large-scale systems is presented. In the proposed two-level approach, using a decomposition/coordination framework, the large-scale system is first decomposed into several interactive subsystems, at the first-level, where a smaller optimization problem is solved at each subsystem. At the second-level, a substitution type prediction method, as a coordination strategy, is used to predict the interaction between subsystems. The coordinator mainly evaluates the next update for the coordination parameters and continues to exchange information with the first-level, so that the overall optimum solution is obtained. It is shown... 

Recent developments in space industry and the great tendency for definition of efficient, precise and low cost missions are the main reasons for the growing interest in satellites formation flight. Regarding the aforementioned, the study of the multiple satellite control methods is the subject of the present project. In this project, the governing equations of motion of satellite formation flight are developed. Based on this development, it is shown that the satellite linear equations of motion like many other linear system presentations, can not sufficiently model the real system. Therefore, some of the most famous uncertainties in space dynamics such as semimajor axis and eccentricity... 

The primary purpose of this research is to model, control and simulate a flexible and fully actuated satellite, equipped with twelve on-off thruster actuators, in rendezvous and docking maneuver. Flexibility of the satellite is modeled by considering two flexible and asymmetrical multi section solar panels with rotational springs and dampers in joints, attached to a central rigid body. Solar panel sections have been modeled in the form of Euler-Bernoulli beam by using assumed mode method and taking into account finite bending mode-shapes. The governing differential equations are obtained using Lagrange method. Then, the dynamic model is validated by comparing the simulation results of the... 

Nowadays electricity power has a key role in developing various aspects of the world. The great importance of fossil fuel power plants come from their large contribution in electricity power generation. Among the different fossil fuel power generation technologies, supercritical power plants have great advantages. They are an advanced power generation technology with high plant efficiency, high coal utilization and low emission. Their complexity and existing many unavoidable uncertainty sources in their dynamic such as changes of ambient temperature, climate condition and wear of components make their control challenging. To overcome mentioned problems and achieving a good performance, a... 

In this thesis, the theory of robust control is applied to design a controller for the longitudinal dynamics of a tail-sitter jet engine unmanned aerial vehicle. The engine thrust deflection is considered as the input controller of the system. The aircraft dynamical model is developed based on the assumption of no aerodynamic loads in low speed flight associated with the hovering condition. The controller is primarily designed using both classical and modern control techniques. Then and synthesis approaches are applied to design the robust controller. The results obtained from different approaches are compared. It is shown that the robust controller techniques are more stable and robust... 

In this thesis, modeling and robust sliding mode control of a snake-like robot with holonomic constraints in tracking of desired paths such as serpenoidal motion is addressed. By considering more real conditions and holonomic constraints, the kinematic and dynamic equations of a semi active robot are obtained using Kane's method. In the next step, based on the obtained results, diverse control theory for getting ability of tracking different paths in environment with different frictions are investigated. Robust control theory is chose to design a controller that has ability of adaption robot’s motion in different environments. For this reason, Sliding Mode Control that has many applications... 

Three-phase voltage source converter (VSC) is vastly utilized in the renewable energy resource and distributed generation (DG) systems interface units due to its high controllability and flexibility. Because of the high nonlinear nature of the system, the gird-connected inverter shows poor performance if the conventional control scheme are used. In this thesis, a new control scheme based on backstepping strategy is presented for control of a grid connected DG systems. The proposed scheme is responsible for regulating the active and reactive power components of the VSC power of the DG system. The VSC of the DG system is connected to a stiff utility grid through an L-type filter. In the first... 

This paper presents a robust adaptive backstepping control design for TREX-600 helicopter with flapping dynamics and dynamic uncertainties in the presence of Dryden wind gust. A nonlinear dynamic model is used to design the controller to let the helicopter track pre-defined time-varying waypoints and heading angles. In order to use the recursive design, the helicopter’s dynamic model is divided into three subsystems, such as altitude subsystem, yaw subsystem and horizontal subsystem. Adaptive backstepping method combines backstepping control and adaptation laws to deal with parameters uncertainties are designed for each sybsytem considering the coupling effects. The global asymptotic... 

Load frequency control (LFC) is one of the important control problems in interconnected power system design and operation, and is becoming more significant today because of the increasing size, changing structure, emerging new uncertainties, environmental constraints and the omplexity of power systems. Therefore, load frequency function requires increased performance and flexibility to ensure that it is capable of maintaining a generation-load balance, following serious disturbances.Real power systems are often large-scale systems which are composed of many interacting subsystems. Therefore, it is difficult to control such systems due to the required inherent computational complexities and... 

In this project, a fault-tolerant attitude control system is developed for thruster-driven satellites. The proposed method has the advantage over current state-of-the-art approaches in that it does not require a fault detection and isolation system. Generalized moments are generated by a robust controller that is designed using mixed sensitivity H_∞ and μ-synthesis by DK-iteration. Moreover, a pulse-width modulation technique with quadratic programming optimization is tuned to map the controller outputs to thruster on-off commands as efficiently as possible. The controller is designed to tolerate up to ±30% perturbations in inertia properties and thrust degradations up to 90% of the nominal... 

The purpose of this thesis is to control the attitude of a tail-sitter UAV in transition phase (from hover to cruise and vice versa). This UAV has a pusher shrouded fan propulsive. Due to the fact that in transition phase the dynamic model of the UAV is associated with a significant uncertainties and the stability is more important than the performance, robust controller has been used. The propulsion part of the tail-sitter UAV can be assumed as a separate ducted fan UAV. In the first step both UAVs have been designed. then, in order to have an accurate model of UAV, the dynamics of actuators, including the engine and servo motor, has been identified. Then, modeling and verification for both... 

Optimizing the energy consumption of air conditioning systems has gained great importance in recent years. In addition, maintaining thermal comfort and air quality in buildings is important. The multi-evaporator air conditioning system, which is a direct expansion system, shows the complex and distributed structure of air conditioning systems due to the thermal connection between zones and its large scale. The modeling of these systems is associated with uncertainties. Therefore, designing a suitable control structure for multi-zone systems is very important to achieve optimal energy consumption and maintain comfort conditions in the presence of uncertainty. Model predictive control has been...