Sharif Digital Repository

This thesis is related to the identification and design of a robust controller for an electrohydrodynamic printer system. As an emerging technology, this printer uses a strong electric field to deliver fluid ink from various conductive materials to the substrate. Modeling this system is complex due to the effect of different variables on its performance. In this project, first a simplified model with numerical solution data of the COMSOL model that is validated experimentaly is proposed. Then, by presenting a new control method that is a variant of an active disturbance rejection control baesd on extended state observer has been controlled. The new control method is actually an amendment to... 

To suppress stick-slip oscillations a controller is designed. However, because the lack of rotary speed at the surface, two approaches to implement this controller is considered: 1) Using an observer to estimate the rotary speed, 2) Using acoustic communication. To implement the second method, we confront several challenges including delay in the feedback loop and noise in communication system. In this thesis, a controller is designed based on prediction of the current rotary speed using its delayed value. It is shown that this system is less sensitive to uncertainty in system parameters compared to the controller based on observer. The performance of both systems in terms of settling... 

The idea of using master_salve robot in Surgical, entered the medical science in a new phase.The surgeon uses the master to perform arbitary actions and slave follow the movements of the master robot in the envirement.To increase the accuracy, it is necessary to transfer information between the robots in both directions, from master to slave and vice versa, that means bilateral teleoperation. But time delay is a serious problem for bilateral teleoperation systems. Even a small time delay will generally degrade the system’s performance and cause instability.Wave variable method based on passivity and scattering theory is an important approach that guarantees stability in the presence of any... 

Low Back Pain (LBP) is one of the most common diseases in the world that according to the statistics 80% of people experience it at least once in their lifetime and a lot of money is spent for its therapy. Finding some methods for prediction and diagnosis of people with LBP from people without LBP helps to reduce these expenses. One of the most effective methods for diagnosing this problem, is the modeling and simulation of its skelomuscular system. However, because of the complications in modeling, simulation and neural control of human spine, it’s not been studied comprehensively. On the other hand, most of the numerical methods are based on optimization and approximation of muscle... 

Cardiovascular diseases stand as leading contributors to human mortality and disability, with heart muscle diseases, particularly acute and chronic failures, prevalent among them. While various diagnostic methods exist, an accurate, non-invasive, portable, easily accessible, and minimally disruptive approach for monitoring, requiring no frequent clinic visits, takes precedence. Early diagnosis and continuous fluid status monitoring through bioimpedance measurements of chest size are crucial in mitigating the mortality associated with these diseases. Utilizing bioimpedance as a non-invasive signal, this system facilitates ongoing vital parameter monitoring, treatment strategy optimization,... 

In today’s competitive market, organizations need to modify their local perspective on enterprise, to a wider scope including supply chain. Focusing on supply chain, helps a more effective and efficient management for organizations. Today’s supply chain management is an inevitable part of enterprise management for achievement of integration between a supply chain’s partners. Oil and gas supply chain, as a complex supply chain, needs an effective and efficient management which uses from different tools and techniques, diagnoses the related errors and drawbacks among upstream partners. A management with such characteristics is scarce, and in this thesis it is tried to present an effective and... 

In this study, adaptive control of HIV infection was investigated based on feedback linearization. First, three state model of HIV infection was simplified to implement the adaptive approaches by using some assumptions. Then, adaptive control method based on feedback linearization was implemented on reduced order and three states infection dynamic model with including the RTIs and PIs drugs effects as control input. The parameter projection method, adaptive nonlinear observer and dynamic anti-windup were employed in implementation of adaptive control method to prevent singularity problem, to estimate system states and to avoid windup problem of external PID controller, respectively. Finally,... 

The fabrication of future electronic and optical devices will require advanced nanofabrication techniques that realize high spatial resolution and high precision in controlling size and position, and that are applicable to various materials. Near-field CVD (NF-CVD) was proposed to solve these problems with no need to perform nanolithography prcesses. NFCVD system has two major subsystems, first vacuum chamber and gas distribution system for delivering parent gases to the chamber and second, a nanopositiong system to keep the probe and the sample in the constant systems.In this dissertation we have set up a piezoelectric nanopositiong system and its driver modules. The positioning accuracy... 

Design of optimal controllers for nonlinear systems and even for linear systems is one of the most important parts of the control science. In optimal controller design, our aim is to maximize or minimize some kind of cost function associated with that particular problem. Such cost functions are usually combining the overall control effort, system’s energy, or some other important specifications of the system. Explicit solution for linear quadratic controllers exists under some mild conditions such as stabilizability of the system. The solution is in the form of a full state-feedback law. But in practical problems, we may not have access to all of the system state variables. The problem can... 

The problem of spacecraft rendezvous on periodic orbits around the L_1Lagrange point of the Earth-Moon system is investigated. For this purpose, the nonlinear relative equations of motion are drived within the contex of the Circular Restricted Three Body (CRTB) problem. Subsequently, several types of rendezvous missionas well as control teqniques are considered for analysis and simulation. Application of different control approaches allows for partial verification as well as comparison of results achieved with various teqniques. The considered control approaches include optimal closed loop Linear Quadratic Regulator (LQR), nonlinear Feedback Linearazation (FL) as well as the nonlinear... 

Image retrieval, simply put, is the process of finding images in a predefined set , that are similar to an image specified by the user. In particular, the user inputs an image as query, and expects to see images similar to the query. Our purpose is to retrieve the images, by means of visual features, without any use of latent information such as tags and annotations.Afer the first round of retrieval, the answers can become more accurate, by means of user feedbacks. In this state, using active learning methods may be usefull. By using active data selection, we hope to achieve the answer faster. Learning based on manifold assumption, is another means which may be used in image retrieval.... 

Feedback-seeking behavior is the effort of employees to get feedback from the environment and around people about their performance. One of the research questions in this field is about the factors that increase this behavior in the staff. Transformational leadership as a leadership style, stimulates, and motivates followers to achieving desirable operational results. In addition, an important consequence of this style could be increasing the followers' capabilities. Transformational leaders are trying to empower their followers to build and empower them, which can provide a strong incentive for employees to move and grow, which may encourage them to have a better performance. One of... 

Cancer is one of the leading causes of death in the world accounting for 7.6 million deaths (around 13% of all deaths) in 2008. Deaths from cancer worldwide are projected to continue rising, with an estimated 13.1 million deaths in 2030 according to WHO. Cancer is a disease caused by normal cells changing so that they grow in an uncontrolled way. There are over 200 different types of cancer because there are over 200 different types of body cells. Various types of treatments are available among them surgery, radiotherapy and chemotherapy are the three major ones. Mathematical models and control theories can be employed to improve the quality of treatment and obtain systematic strategies of... 

Degradation of signal to noise ratio (SNR) in today's low voltage circuits has been a challenging problem for analogue circuit designing. This problem is produced due to supply voltage reduction and noise level consistency in today's analogue circuits. Great efforts have been done in literatures for noise reduction in some analogue circuits, like low noise amplifiers, but there is no general method for noise reduction in active filters and introduction of a general method for noise reduction in active filters which are in vast usage in all analogue circuits, has always been demanded by circuit designers. In this project, a general method for noise reduction in active RC filters is introduced... 

User cooperation is an important concept in wireless networks to achieve best performance subject to low cost. Dynamic and broadcast natures of wireless networks are two indispensable characteristics of these networks. Therefore, when a user transmits his signal to the receiver, other users in his neighborhood may receive the signal as well. Hence, these neighbors can decide to cooperate with each other in transmitting their messages to the receiver. On the other hand, due to the dynamic nature of the wireless networks, one can assume that each user has some knowledge about the interference signals or the fading coefficient that are not known to the other users. Therefore by utilizing user... 

In this study, the two rigid body modelling of a Coanda air vehicle (one rigid includes rotor and propeller and the second rigid includes the other parts of it) has been developed using Newton’s and Euler’s laws, and its motion was simulated in climb and forward flight conditions. Air vehicle propulsion force and moment have been modelled by employing the blade element momentum theory. In order to model the forces acting on the air vehicle, the drag force has been estimated by the results of analytical and computational fluid dynamics methods for the case of climb flight and by using experimental data of a cylindrical body for the forward flight. For modelling the control surfaces of this... 

In this thesis we introduce a new methodology to solve the problem of multi-objective control design of linear output-feedback with a constraint on the order of controller. This problem can be formulated as a set of linear matrix inequalities and an additional rank constraint. This constraint is highly non-convex and makes this optimization problem NP-hard. The proposed methodology results in methods which are multi-step and in each step a convex optimization problem shall be solved. This methodology can consider any combination of different design objectives such as H2 performance, H1 performance, passivity and regional pole assignment. In the development of described methodology, a... 

In this thesis, chaotification of dynamic systems in general and chaotification via full state linear feedback are investigated particularly. Studying chaotification is a problem over investigating dynamics of chaos and controlling it, so studying this problem needs to have some general information about chaos and its dynamics. Because, this is a new case, researches in this field are not enough and actually, there is no paper on application of chaotification. Reviewing literature in this field shows that in solving problems of chaotification, there is no notice on applications and ability to apply it on physical systems. So one of the most important aims of this thesis, is to find an... 

Continous blood glucose control has great importance for type 1 dyabetic patients. In this thesis, several types of controllers including: PI controller, model predictive controller base on state space model, linear model predictive controller base of linear input-output model and non-linear model predictive controller base of Hammerstein model have been used to regulate blood glucose of patients with type 1 diabetes. These models are identified using least squars method. Performance of these controllers is tested and the best one is introduced. For rejecting meal disturbances, a feedforward controller has been designed. Combination of feedback and feedforward controller would properly... 

Low back pain (LBP) problems are of concern to many researchers specially physiologists, biomedical engineers and... .biomechanical models can help us to furthering our knowledge of the mechanical characteristics of the spine and its neural control to know more about potential mechanisms of injury. This thesis involves computational model of lumbar spine to generate and control its flexion-extension movement.
Model has involved 7 links: 5 lumbar vertebrae, pelvis and trunk. Desired trajectory has been generated for rhythmic and discrete motion by the central pattern generators (CPGs). And then controller has produced torque of joints to track desired trajectory. CPGs have been...