Sharif Digital Repository

Dynamic modeling and process control, especially the equipment of bioreactors and fermenters, have always faced many challenges due to the complexity and high uncertainty of the kinetics of environmental reactions. Among these, semi-continuous fermentation for bioethanol production is one of the important technologies in biochemical industries. The problem of modeling as well as controlling the use of the main discontinuous and semi-continuous methods of ethanol production is the lack of uniform state conditions and the possibility of aerobic and non-aerobic multiplication conditions in two ways. The main goal of this research is to obtain a new method in modeling bioethanol fermentation and... 

Vibrations in HAWT reduce their efficiency and increase maintenance costs. In this paper, the blade edgewise vibrations are reduced by using several actuators in different parts of the wind turbine blade and optimization of the number and locations of actuators. The wind turbine blade dynamic behavior is investigated by using dynamic modeling. The actuators are trusses that are located inside each blade and apply control force to different parts of the blade. Active control force is applied to reduce edgewise vibrations. The designed controller is applied and simulated on NREL 5MW wind turbine. By applying the controller, the edgewise vibrations of wind turbine blades are significantly... 

Due to the importance of recognizing the underwater and the existence of danger to human life in this environment, the use of AUVs has greatly expanded. To build and use these vehicles, we need to model dynamic behavior, and control these systems. The nonlinear dynamics of the AUV makes it difficult to use common linear controllers. On the other hand, the coefficients used in dynamic equations have uncertainty and changes, and as a result, dynamic analysis may be probably un-accurate. If the controller is designed, the controller must be self-tuning and robust to be able to withstand changes and uncertainty. Adaptive control is an approach for controlling such systems. The main idea in... 

One of the most surprising lessons of dynamical systems theory is that the phase spaces of simple nonlinear systems may contain strange attractors. For certain simple systems, such as pendulum, direct observations of the phase space and finding strange attractors are possible. But physical systems in which all the relevant dynamical variables can be simultaneously monitored are relatively scarce. Takens’ theory shows how a time-series of measurements of a single observable state can be often used to reconstruct qualitative features of the phase space of the system. In this research, using the time-series of one measurable state, an algorithm is proposed to control chaos. The approach... 

Spacecrafts formation flying is defined as tracking or keeping of desired distance, relative position and attitude of two or more spacecrafts during a maneuver. Division of tasks between various smaller spacecraft’s and so reduction of need to advanced technologies, increase in reliability in system and doing special missions like 3-D imaging of planets and combining parameter measurements are some advantages of this method. For development of this method, in this thesisin addition of reviewing the common methods in spacecraft’s formation flying, we are supposed to provide a simple and new method called distributed control for controlling a formation of spacecrafts. Additionally by providing... 

In this research, we investigate the role of oil and degree of dependence to it on nexus between financial development and growth volatility. The link between financial development and growthvolatility has been the focus of extensive literature, but no empirical study has been investigated the role of oilin relationship between financial development and growth fluctuations. By using information of 78 developing countries (11 oil exporting and 67 non-oil countries) during 1983-2008, we construct a dynamic model. Difference GMM technique is used to estimate the model. Our findings show that negative impact of financial development on volatility of GDP, Investment and Consumptiongrowth is... 

This work concerns with experimental and modeling investigation of the asphaltene damage removal using ultrasonic wave irradiation. A specific core holder apparatus was designed and utilized for in situ ultrasonic exposure to damaged core plug at different conditions of exposure time, ultrasound power and distances between sound source and plug. Injection of many pore volumes of an asphaltenic crude oil was used for creating asphaltene induced damaged in porous media through permeability measurements. The deposited asphaltene during oil injection as well as asphaltene removal due to ultrasonic exposure was evaluated using IP-143 analysis. The results revealed that ultrasound application... 

Due to high cost and ineffectiveness of molecular models a new method for coupling continuum models with molecular models is used. In this method, the continuum and molecular domains are overlapped. Comparing the results obtained from the concurrent simulations and molecular dynamic simulations proves the accuracy of the method used. The method is used for modeling single layered graphene sheets, stress contours are presented for multiscale and both static and dynamic simulations of concurrent. For multiscale simulations two different carbon nano tubes are investigated and strees-bond angle and strees-bond length are also presented  

Nowadays, single-crystal nickel-based superalloys are widely used in the manufacture of gas turbine blades in the aerospace industry due to their high resistance to creep, fatigue and corrosion at high temperatures. The superior behavior of these materials at elevated temperatures is a result of their two-phase microstructure, which includes the matrix phase (γ) of nickel and the precipitate phase (γ') of Ni3Al intermetallic compounds with a high volume fraction. The aim of this thesis is to develop computational modeling tools to study the creep deformation of single-crystal Ni-based superalloys. At high temperatures, the creep deformation of Ni-based superalloys is determined by the atomic... 

Auxiliary Power Unit (APU) is a single spool turboshaft engine aimed to start the main gas turbine engine on the ground as well as to supply the necessary power to the auxiliary and electrical equipment during an engine emergency shut down. Similar to the main gas turbine engine, the performance of APU depends on the altitude. Hence, a control system with an appropriate logic is required for a dual function APU which provides electrical power as well as pressurized air through a generator and load compressor, respectively. It should be emphasized that while the output of the generator remains almost not affected with the altitude, the performance of the load compressor is altered by this.... 

Microrobots are generally suitable for implementation of certain works in miniature dimensions such as micro assembly, microsurgery, adaption with small animals and so on. In this way, there is special position for mobile microrobots capable of moving in the range of more than theirs dimensions. Achivieng to high resolution and high speed locomotion are the challenging issues in the microrobot’s development in which much effort has been done.The goal of this project is dynamic modeling and velocity control of an A-shaped microrobot with with nanometric locomotion. During this project, first the dynamic modeling of microrobot is investigated and simplified based on the previous studies.... 

Fish robot has attracted many attentions in the last decade due to several types of its applications. Many researches have been done recently on this type of robot. Dynamic modeling and control of a fish robot are important and challenging problems. This issue has a great influence on design, manufacturing, efficiency and control of the fish robot. According to the literature review, it seems that no exact analytical model exists for predicting the propulsive forces which are used in controlling and simulating dynamic behavior of the robot. Fortunately, Lighthill has proposed an analytical relation to predict propulsive forces of carangiform fishes in his research. Large amplitude elongated... 

The aim of this study is to design a control system for an autonomous underwater vehicle and evaluate this system for different missions. Due to the non-linear behavior of the target robot, both linear and non-linear behavior of the system was studied. Model Predictive control method has been implemented since it can outline both linear and non-linear controllers. The first non-linear dynamics of this robot, maneuvering equipment, and external disturbances (waves and ocean current) were modeled. Then, to design the linear controller, the equations of motion have been linearized around the working point(cruise speed). In order to analyze both designed controllers, various duties have been... 

In this project dynamic effect of changes in gas turbine load on power plant, reforming and Co2 capture section is investigate. The reason for study of effects change of gas turbine load is that gas turbine determines the performance of the other parts in combined cycle including gas cycle and change of gas turbine load can alter the load and the performance of other parts in the power plant and in other process such as production of synthesis gas and carbon dioxide separation unit. One Autothermal reactor and eight sewgs reactor are utilized to produce gas turbine fuel which is mainly consist of Hydrogen. this part of thesis is to be implemented in the gPROMS from process system enterprise... 

This thesis is concerned with the modeling and simulation of twelve degrees of freedom parafoil-payload system, as a multibody aircraft configuration. This 12-DOF dynamic model represents three degrees of freedom each for rotational motion of the parafoil (including suspension lines and canopy) and payload, and three degrees of freedom for translational motion of the parafoil, and one degree of freedom for relative translational motion of the payload, also two degrees of freedom for rotation of the canopy frame respect to the parafoil frame.
For evaluation of the flight dynamic behavior of parafoil-payload system, the nonlinear differential equations of the system have been derived and... 

Compression systems are widely used in industry. Dynamic Modeling is a necessary step in design procedure of a safe compression system. A dynamic model should be adequate and simulate dominant elements of system. One important element of industrial compression systems is downstream pipelines. In this work, a dynamic model including pipeline acoustics is developed. It is accepted that changes of working gas molecular weight can cause inception of instabilities in compression systems. The dynamic model used to study mechanisms of these instabilities. A conventional control system is modeled and tuned for the compression system. The ability of this control system to prevent such instabilities... 

This research aims to study the identification of inertia parameters (IPs) of space-robots with the main focus on Active Space-Debris Removal (ASDR) application. In many future space missions, like ASDR, the spacecraft should handle objects (like debris) with unknown IPs. To control and stabilize the spacecraft, it is crucial to identify the dynamic model of the spacecraft in such these missions. On the other hand, uncertainties in the IPs of spacecraft (including space-manipulator) make the identification problem more complex. To overcome the complexities related to mathematical representation of identification equation, a new mathematical tool called Matrix-Set is proposed to develop the... 

Due to the growing rate of photovoltaic plants in power systems, in the future years this type of plant will have significant contribution in electrical energy generation. For this reason, the impact of photovoltaic plants on various aspects of power system operation should be investigated. In this research dynamic impacts of photovoltaic plants on small signal stability of power systems are analyzed. For this purpose, improved dynamic equivalent models are developed for large-scale photovoltaic plants, based on integration of the plant modules. It is shown that the usual assumption of ideal DC power supply at the input of plant inverter is inappropriate, and that the DC-DC converter and DC... 

In this research, the dynamic model of a quadrotor-cable airborne wind energy system is presented. These systems have received a lot of attention in recent years and many examples of them have been designed and built. In addition to comprehensive system modeling, cables and quadrotor in the quasi-stable autorotation phase are modeled separately. These models can be used in other fields in addition to wind energy systems. One of the applications of this thick cable model is in the marine industry.In this research, Newton-Euler method has been used for modeling. The cable model is considered and developed as rigid elements with joints with rotary springs and dampers. The quadrotor model is... 

The “hypothalamus-pituitary-adrenal” axis is one of the most important axes of the human body, and cortisol is one of its key products, which plays an essential role in the immune system, stress management, and many diseases. Appropriate modeling and simulation of this axis can help us to understand how the body reacts to stress and inflammation, to examine relevant diseases, and how drugs affect the body. In this study, by combining an axial model of the hypothalamic-pituitary-adrenal axis with a model of adrenal cells, a bi-level model including several time delays has been developed that can predict the effect of stress on this axis. Some parameters of the model have been modified through...