Sharif Digital Repository

Nowadays, there are various applications for swarm robots in different fields such as agriculture, healthcare, and entertainment. Among these, the field of agriculture is of greater importance due to the increasing population and the growing need for food resources. To address this need, industrialization of agriculture and the use of swarm robots have been proposed as a solution in most developed countries. Despite extensive research in this area, there are still challenges in implementing swarm robots. In many of the mentioned applications, determining the position and orientation of the robots relative to each other at long distances and accurately perceiving their surroundings are vital... 

Algorithms for online identification of parameters of a satellite’s moment of inertia tensor based on two methods (recursive least squares and Kalman Filter) is presented and compared with each other. It is assumed that the satellite actuators are three orthogonal reaction wheels. The only available sensor is a 3-axis rate gyro, which measures the angular velocity of satellite in body coordinate system. For validation of algorithms on earth, a similar identifier was designed for a satellite simulator. Due to difference in Dynamics of satellite and satellite simulator, capability of identifying center of gravity was added to algorithms. In order to account for friction in air bearing of... 

Nowadays precise nano positioning plays an important role in micro systems. Precise positioning at nano scale plays a basic role in nano science such as micro -robotics, solid state physics and photonics. Manipulating matter in a molecular scale creates a dramatic change and restruturing in macro scale engineering. During this research a novel TEM micro actuator is designed and fabricated based on calibration criteria. This structure was fabricated with SOI wafer (silicon on insulator) in micro scale level for the first time in Iran. This compliant consists of 12 TEM actuators end in 3DOF (In-plane) motion. The new micro actuator operates based on the thermal expansion due to voltage. Each... 

A swarm robotic is made up of a number of similar robots (identical) that these robots alone do not have any potential, but they can with each other have considerable potential. In recent years, engineers have become more interested in swarm robotic. Swarm robotic allows the use of several colleague robots instead of an advanced robot that eliminates excessive complexity and expensive equipment. The purpose of this study is to provide a method for solving the crossing problem and interfering between robot swarms. In previous studies conducted at the Sharif University of Technology, the main goal was to design algorithms for the swarm behavior of a swarm robotic. In this research, the aim is... 

In this paper, controlling the cutting force of an end-milling process using a supervisory fuzzy controller has been investigated. The proposed control consists of an ordinary fuzzy controller and a fuzzy supervisor. In a machining process, there are several parameters which do not contribute to the force control system directly. Therefore an ordinary fuzzy force controller is suitable when these parameter have only small amount of variations. Since in practice this assumption is not valid, then a supervisory fuzzy controller has been added to the system. The designed fuzzy supervisor, inspects the dynamic behavior of the cutting force, estimates a pre-defined ‘sensitivity’ parameter and... 

Nowadays, Specific applications of micro-mirrors in MEMS industry as actuartors have been found. In optical networks, these instruments are used to transfer data between optical fibers as an optical switch. According to the high desired precision for the relevant applications, many different aspects should be considered in controlling of these systems. Some of these criteria include: high speed response, overshoot elimination, minimal energy consumption by regulating the system inputs, minimal vibration, consideration of system uncertainities and some unmeasurable state variable, and system rubostness against environmental disturbances. In this research by addressing all of these... 

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... 

Over the past years, several approaches have been used for navigation. Along with the advancement of technology, complicated navigation systems such as inertial navigation system and global positioning system have been employed. These navigation systems have their own strengths and weaknesses. To improve overall system performance they are integrated together as one system.
Presented research aims at developing the integrated navigation system through particle filters. In this study, after a brief overview of the data integration techniques, several techniques which are more common and have better performance than others are examined. This contribution concentrates on filtering methods... 

Air-handling unit (AHU) is one of the installations that is responsible to control the temperature and humidity inside a space using the heating, cooling, humidifier and drying air. At present, energy efficiency in building is an important issue to maintain the comfort conditions. One of the most common ways to optimize the performance of industrial installations is the use of control systems, which leads to the reduction in both of the costs and energy consumption. In this research, a multivariable nonlinear dynamic model of the AHU with one zone in the VAV (variable air volume) system for working in summer is considered. At first, introduction, limitations and driving the equations for the... 

Due to various applications of human motion capture techniques, developing low-cost methods that would be applicable in non-laboratory environments is under consideration. MEMS inertial sensors and Kinect are two low-cost devices that can be utilized in home-based motion capture systems, e.g. home-based rehabilitation. In this work, an unscented Kalman filter approach was developed based on the complementary properties of Kinect and the inertial sensors to fuse the orientation data of these two devices for human arm motion tracking during both stationary shoulder joint position and human body movement. A new measurement model of the fusion algorithm was obtained that can compensate for the... 

The design and implementation of the hybrid control method for a three-pole active magnetic bearing (AMB) is proposed in this paper. The system is inherently nonlinear and conventional nonlinear controllers are a little complicated while the proposed hybrid controller has a piecewise linear form, i.e., linear in each sub-region. A state-feedback hybrid controller is designed in this study and the unmeasurable states are estimated by an observer. The gains of the hybrid controller are obtained by the LQR method in each sub-region. To evaluate the performance, the designed controller is implemented on an experimental setup. The experimental results show that the proposed method can efficiently... 

Fault detection in swarm robots is one of the most important issues that has drawn a lot of scientists’ attention. Previous studies have shown a lot of problems regarding this issue, such as dependency of data-based methods to mission and high complexity of model-based methods on the condition that nonlinear models are used. Extended information filter is an applicable method for fault detection because it could turn the inverse of a big matrix to a simple summation of information that is so desired in terms of calculations. The goal of this study is to identify the agents with fault in swarm robots online by modifying the extended information filter. In this study, it has been attempted to... 

Minimizing the entropy function of a chaotic system is a recently presented novel technique for stabilizing the unstable periodic orbits embedded in a chaotic attractor. Having the states of the system known, this method suppresses chaotic behavior while the mathematical model of the system is not required. The entropy in the sense of Shannon is defined for the system as a measure of the irregularity of its behavior and considered as an objective function to be minimized. Control action is designed in a way that this entropy decreases. Rather than the previously used gradient descent algorithm, optimization algorithms inspired by nature-oriented swarm intelligence− particle swarm... 

In this thesis, implementing parametric resonance for the purpose of improvement in sensitivity of MEMS gyroscopes is studied. Based on a parametric study on effect of each factor on the sensor’s performance, the desired values for each parameter is determined. Stability of periodic orbits is studied using Floquet Theory. In addition, three expositions are defined and proved in order to make Floquet Theory applicable for stability analysis of origin. Based on this analysis, the relation between stabilities in the system and occurrence of parametric resonance is illustrated. Due to the complexity of dynamics of a parametrically excited MEMS gyroscope, bifurcations are observed in performance... 

Recently, parametric excitation has been proposed and experimentally proven to provide micro gyroscopes with robustness to parameter variations and enhancement of sensitivity [L.A. Oropeza-Ramos, C.B. Burgner, K.L. Turner, Robust micro-rate sensor actuated by parametric resonance, Sensors and Actuators A: Physical, 152 (2009) 80-87].The first part of this thesis aims at investigating the nonlinear dynamics of MEMS vibratory gyroscopes with parametric excitation which can be represented by a minor variation of nonlinear Mathieu equation coupled to a Duffing oscillator. Our approach is based on analytical frequency response derivation via method of multiple time scales. Stability of responses,... 

Nowadays, micro systems are one of the most important scientific and industrial tools and become very important. Most of these systems are working based on deflection of a micro beam. As a result, studing performance of micro beams and controlling them have significant importance for science and engineering.Amoung micro beams cantilever and clamp-clamp beams, which are actuated by electrostatic or piezoelectric actuators, are very applicable. For example, micro cantilevers are used in Atomic Force Microscopy, Microswitches, acceleromiteres, and micro clamp-clamp beams are employed in micro mirrors and Grating Light Valves.In this research, a micro cantilever actuated with a piezoelectric... 

Piezoelectric Energy Harvesters (PEH)’s are devices that by means of Piezoelectric effect, convert ambient vibrations directly into electricity.
PEHs are often modeled as a cantilever beam with two piezoelectric layer attached to its sides. Due to their high energy density, small dimensions and adaptability to harsh environment, PEHs are referred to be a suitable substitute for batteries in the near future.
In this study, a new design of PEH is introduced in which a piezoelectric actuator is placed within web of a PEH so that by applying appropriate voltage to it, the distance between the two flanges of the beam, and accordingly the moment of inertia of the beam, is adjusted such... 

Living creatures have a significant ability to move on various surfaces and to pass obstacles and because of this many robots have been made by inspiring their moving mechanisms. One of these mechanisms that is sometimes ignored because of its nonlinear dynamics and instability and hybrid dynamics of system, is jumping mechanism. In this project a two dimensional multi-legged jumping robot is designed that can jump, do a handspring during jump and land on its other side keeping balanced. The robot moves forward by repeating such procedure. Doing a handspring instead of normal jump uses less energy.This robot uses geometric control method to handspring during flight. This method ables robot... 

Nowadays, micro systems in many area of science and technology have special importance and status. The main function of these systems is based on the deformation of a beam at micro scale. Therefore study of behavior and control of micro-beams will have a great importance. Among micro-beams, clamped-free and clamped-clamped micro beams that actuated by piezoelectric and electrostatic actuators have wider applications. For example, clamped-free micro-beams are used in atomic force microscopy (AFM), micro switches, mass sensors and micro-accelerometers and clamped-clamped micro-beams are used in micro mirrors and Grating Light Valves (GLV). In this thesis, the studied system is clamped-free... 

As the leading kind of multi-rotors, quadrotors have become one of the most popular Unmanned Areal Vehicles (UAVs). These robots are very agile, but their speed is limited when performing decent maneuvers. In this project, a special quadrotor with dihedral-rotating arms is presented in order to increase the decent velocity of the vehicle. The conceptual and detailed designs of the vehicle are presented first, followed by the construction of the quadrotor. The fabricated quadrotor measures 25 cm in size, has a weight of about 1 kg, and can support up to 70 degrees of dihedral angle. Afterwards, the dynamic equations of the dihedral quadrotor are driven and simulated. The effects of dihedral...