Sharif Digital Repository

Direct Torque Control (DTC) is one of the vector methods to control Permanent Magnet Synchronous Machines (PMSM). In order to achieve an appropriate control in vector control methods, an accurate estimation of flux is indispensable. Flux estimation should be fulfilled in a wide speed range without considerable dependence on motor parameters. Prevalent flux estimation methods are based on integration of stator voltage which is not feasible in low speed, or performed based on assumption of decoupled equations on d and q axis which is not precise for applications with fast dynamic. Different flux estimation methods are investigated in this thesis with the aim of improving the flux estimation in... 

In this thesis, a decentralized controller for trajectory tracking of robot manipulators is developed. Proposed control scheme use uncalibrated joint torque sensors. Recently, it has been shown that the use of joint torque sensing results in a simplified manipulator model and reduce the need of dynamic model of links for controlling. In this thesis, we use the special lower triangular structure of this simplified model for decentralized control of manipulator. For the first time a smooth decentralized law is designed which makes both position and velocity tracking errors of robot manipulators globally converge to zero. Against most of previous work in decentralized control of manipulators,... 

Analysis and design of power systems are challenging due to ever increasing dimension of the system and also the nonlinearities involved in the system. The conventional approach is to use linear analysis tools and then investigate the nonlinear impacts by the means of computer simulations. This requires great deal of trial and error and it is not always a timely approach. In this project, we initiate a comprehensive nonlinear analysis for a single-machine infinite-bus system by studying a Hopf bifurcation in its dynamics. We use results of our nonlinear analysis to study how a capacitive compensation such as TCSC works. Subsequently, we design a nonlinear controller for a PSS to have... 

In this research, the main purpose of the controller design is in the second region of operation of a wind turbine, which involves absorbing the maximum energy from the wind. WindPACT 1.5MW turbine has been investigated and the power coefficient of this turbine has been obtained using WT-PERF and FAST softwares. Simulations show that the results of both methods are well matched. Then, using ANFIS, a method for estimating the wind speed is derived from the data obtained by FAST. Inputs to the ANFIS system are the turbine aerodynamic power, rotor speed and blade pitch angle while the output of ANFIS system is the estimated wind speed. The maximum power coefficient of the wind turbine occurs... 

Thus far, there has been a great attraction toward the optimal flight path planning problem. Terrain following/avoidance (TF/TA) flight is one of the most significant applications of this issue. To prevent from detection by the radars, fighter aircrafts, cruise missiles and helicopters often have to fly as close as possible to the surface during the operations. Such types of maneuvers are much more demanding and effortful than to be designed and implemented by human. The optimal TF/TA guidance system design comprises three phases: optimal path planning, closed-loop control system design for trajectory tracking and sensor blending to match the onboard and measured terrain data. So far, the... 

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... 

In this research, we explore a novel approach for controlling continuous-time chaotic systems with unknown equations and exclusively using one measurable state variable. In pursuit of this objective, the study unveils two efficient approaches: one tailored for autonomous systems and the other designed for systems with external excitation. In both approaches, our methodology centers on minimizing the conditional entropy which is derived based on the conditional probability distribution of the only observable state variable. Considering the numerical nature of entropy calculations in practical issues, we have employed the Poincare map to discretize the continuous-time system. In the following,... 

In recent years, autonomous unmanned aerial vehicles (UAVs) have attracted considerable amount of interest because of a wide area of applications and a lot of advantages. UAVs have been extensively used for military operations that include tracking, surveillance, active engagement with weapons and airborne data acquisition. UAVs are also in demand commercially due to their advantages in comparison to manned vehicles. These advantages include lower manufacturing and operating costs, flexibility in configuration depending on customer request and not risking the pilot on demanding missions. Quadrotor, which is a kind of rotary wing UAVs, has many advantages such as the vertical take-off and... 

The huge capability of high resolution satellite imageries (HRSI), that includes spatial, spectral, temporal and radiometric resolutions as well as stereoscopic vision introduces them as a powerful new source for the Photogrammetric,Remote Sensing and GIS communities. High resolution data increases the need for higher accuracy of data modeling.The satellite orbit, position, attitude angles and interior orientation parameters have to be adjusted in the geometrical model to achieve optimal accuracy with the use of a minimum number of Ground Control Points (GCPs). In order to obtain high resolution and definition imaging for many applications including surveillance, target tracking, and... 

In the class of unmanned air vehicles (UAV), there is a class entitled as Quad-rotor that engineers pay much attention due to specific features to them. Main applications of this class are because of vertical take-off and landing capability and high controllability. This class has high controllability in environments with high barriers because of the inherent imbalance. All of the Quad-rotors have already studied, had a fixed structure. So the designer's main focus was on improving the guidance and control systems and almost all forms of linear and nonlinear control methods and fuzzy, adaptive and robust control have been investigated. In this study variable structure is examined instead... 

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.... 

The field of microrobotics has seen tremendous advances in recent years. Potential high impact applications of untethered microrobots such as minimally invasive diagnosis and treatment inside the human body, biological studies or bioengineering, microfluidics, desktop micromanufacturing, and mobile sensor networks for environmental and health monitoring are reported. However, There are significant challenges in microrobotic technology, including energy resources, control systems, reliability and safety, design and manufacturing of micromotors and localization. In this work, overall size scale being micron scale is emphasized where mobile robots able to fit in spaces smaller than a millimeter... 

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... 

Considering uncertainty is of great importance in the design of controllers for dynamical systems because the existence of uncertainty is inevitable in the modeling of almost all real-world systems. There are numerous methods and strategies for dealing with the control of uncertain systems in control systems theory including adaptive and robust approaches. The former one is more suitable for cases in which the information about uncertainty is very poor compared to robust techniques that are applicable in the cases more data is available about uncertainty. For instance, where there is no data about the direction in the actuator model, adaptive control methods are the only applicable choices.... 

Control of a group of autonomous surface vessels with realistic dynamic for circling mission is distributed with the aid of Lyaponov and graph theory. in this brief, to obtain a cooperative controller, new coordination transfer are presented and graph theory is used to illustrate the communication between the agents. With the aid of Lyaponov theory and graph application, Decentralized and scalable controllers are designed for group of autonomous vessels to converge to desired geometry to circling a specific target. Because of the realistic dynamics, Non-Holonmic dynamics and turning constrains of the vessels are considered in the design process. The advantage of proposed controller is: it... 

Three different feedback linearization control methods are applied to nonlinear control of type I diabetes mellitus model. One is exact FBL and the two others are approximate manners based on approximations of the nonlinear system and its duality one-form, utilizing uniform approximation and a homotopy operator, respectively. An extended luenberger observer is also employed to observe the required states of designed compensators. The nonlinear compensators are designed based on a minimal model and applied to the minimal model, as well as Sorensen’s physiological model. In addition to the mentioned close-loop control strategies, a discrete control strategy based on an optimization problem is... 

Design and development of Unmanned Aerial Vehicles (UAVs) has been a hot topic in the past decades. In particular, Vertical Take Off & Landing Vehicles (VTOLs) have been extensively studied and are under constant development. Quad rotors are one of the major subcategories of VTOLs and a lot of effort have been devoted to their control optimization. In the present study, we have utilized a novel transformer quad rotor structure that can change the angle between its arms. This structural change is a type of design feature modification that can effect the moments of inertia by changing the flight dynamics of quad rotor. Modification of height difference between adjacent rotors, while avoiding... 

Nowadays, autonomous underwater vehicles (AUVs) are implemented to carry out various activities under water. Amongst applications of these vehicles we can mention monitoring of marine creatures, mine installation and neutralization, and many military applications. The objective of this research is designing a control algorithm for underwater vehicles such that an under actuated vehicle can reckon a moving target as a reference and whilst chasing it, vehicle can keep a fixed distance from this target. First the dynamics of underwater vehicles are modeled and in this modeling different effects due to under water motion such as drag force, buoyancy force, and also added mass are included... 

In this thesis, a new procedure is presented for control and analysis of a group of autonomous underwater vehicle achieving flocking motion by using a fuzzy-logic-based attractive/repulsive function. Two cooperative control laws are proposed for a group of autonomous agents to achieve flocking formations related to two different centers (mass center and geometric center) of the flock. The first one is designed for flocking motion guided at mass center and the other for geometric center. Desired path for AUV’s has been developed using Virtual agents with mass point dynamics. Smooth graph Laplacian is introduced to overcome the difficulties in theoretical analysis. A new fuzzy-logic-based... 

Coaxial helicopters are one of the kinds of helicopters that have two main rotors spinning opposite to each other. These helicopters have no tail rotor and their size varies from very small (about 100 grams) to large (manned). The widespread use of helicopters justifies controller design for them.
In this research, at first step coaxial helicopter is controlled with two linear control methods. In many control problems linear control responds to the diverse needs. In addition it has good robustness in situations like uncertainties, disturbances, noise etc. For this purpose, nonlinear dynamic model of helicopter is used in the beginning. This model is linearized around hover condition to...