Sharif Digital Repository

Satelites formation which is a specic spatial conguration of satellites, is of great importance in design and control of satellite systems. Reducing the required power to maintain that conguration, while imposing complicated dynamics on the system, connecting satelites through tethers has recently attracted researchers' attention. Developing a new model based on which the motion of the satellite formation will be expressed through simple equations, followed by the study of how the tether length control participates in the orientation control of the system, are the principal aims of current research. First, a new model is proposed for a group of tethered satellite for- mations, and based on... 

Swarm is coordinated group action that usually done with little communication among its members. Using several simple members instead of the complicated ones reduces cost, simplifies system and increases the reliability. On the other hand, the mission can be done faster. This thesis is done in two general sections; theoretical and experimental parts. At first some important missions are simulated in MATLAB/Simulink such as aggregation, dispersion, flocking, obstacle detection, obstacle collision avoidance and orbiting around the obstacle. Orbiting around the obstacle is simulated formation flying and a constellation of satellites (such as GPS systems). The methodology is artificial potential... 

In this research application of Ionic Polymer Metal Composite (IPMC) as actuator in a deformable ring capable of locomotion is studied. Such a deformable ring moves as a result of gravitational force acting on its body when its shape changes. A deformable robot made of IPMC can be used in exploration, search and rescue missions in future, where using conventional robots with rigid bodies and actuators is impossible. Large deformation induced by small stimulating voltage, low stiffness and the sensing characteristics that in future work can be used in feedback control make IPMC a good choice for such an application. In this work first a model for IPMC is introduce that can be used in... 

This study is about real-time hybrid motion planning for autonomous UAVs in dynamic environments. The algorithm is based on system dynamic quantization to trim trajectories and maneuvers, constructing a library of primitives which guarantee the controllability of the system. Random algorithms introduced in literature of motion planning have an offline phase, reducing the computational complexity of online phase. By using dynamic quantization, we have achieved a new totally online algorithm, increasing the probability of finding a solution. Dynamic programming is the core of this algorithm, instead of offline calculations in before random algorithms. In order to decrease the exponential... 

Swarm robotics has attracted a lot of researches in recent decades due to its ability to overcome complexities despite of simple hardware used in each member of swarm. Developing control algorithms which can address connection, consensus and average consensus, position control, formation and swarm movement, is one of the main problems in the study of multi-agent systems and swarm robotics. Even though such methods have been developed and used by researchers for a few years, theoretical and operational issues still exist in the use of robotic swarms. For example, in leader-follower method, presence of repellent coordinator agent results in disruption in movement of other agents. Also... 

The aim of this project is decentralized control of a group of robots (swarm robots); such that the aggregation maneuver, leader following, Identification and imaging the target, will be performed so good as to make a three-dimensional model of the target from these images. Swarm robots consist of a number of similar and limited features robots which interaction in a group of robots, will lead to special features for the group. Any agent of group decides what to do only with its local information from the environment. Swarm robots are more applicable for the jobs in which a distributed perception from the environments needed, for example space exploration and military operations.In this... 

Proportional-Integrator-Derivative (PID) controller is used in a wide range of industrial and experimental processes. There are a couple of offline methods for tuning PID gains. However, due to the uncertainty of model parameters and external disturbances, real systems need more robust and reliable PID controllers. A compelling example of these types of systems is Quadrotor. In this article, a self-tuning PID controller using Reinforcement Learning for attitude control of a quadrotor has been investigated. In the proposed method, an Incremental PID, which contains constant and variable gains, has been used, and only the variable ones have been tuned.In this research, the model-free... 

Inspired by the agility of animal and human locomotion, the number of researchers studying and developing legged robots has been increasing at a rapid rate over the last few decades. In comparison to multi-legged robots, single-legged robots only have one type of locomotion gait, i.e., hopping, which represents a highly nonlinear dynamical behavior consisting of alternating flight and stance phases. Hopping motion should be dynamically stabilized and therefore, presents challenging control problems. A large fraction of studies on legged robots have focused on modeling and control of single-legged hopping machines. In this research, somersaulting is introduced as a kind of hopping motion for... 

The aim of this research is to measure the area of agricultural lands using realtime aerial images. This project is divided into two parts. In the first part of the project, five segmentation neural networks based on YOLOv8 models were designed. After collecting 734 images of agricultural lands, they were trained, and among them, the nano model was selected with 89% accuracy, 88% recall, and an inference time of 49.8 milliseconds. In the second part of this project, the internal characteristics and distortion elements of the camera used were identified through the calibration process using a chessboard. This process was carried out using 81 images and hadan RMS of 1.178. Also, the elements... 

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... 

The idea of using groups of simple autonomous robots instead of one or limited number of very sophisticated robots is inspired by flocking behaviors of animals. Distributed control structures and artificial swarming have attracted lots of studies in robotics. There are many applications for robotic swarms in which members are very simple robots with low communication capabilities. These robots communicate only within very limited distances. In this thesis, a homogenous robotic swarm with at least two robots is assumed. Swarm robots are considered to be dimensionless with no time delay, which is a normal assumption in this field of studies. Robots move in planar space and their behaviors are... 

Nowadays, continuous systems such as strings, bars, beams and plates have become widespread in science and engineering applications. To achieve the control purposes of continuous systems, most of engineers use discretization techniques to reduce the governing partial differential equation (PDE) into a set of ordinary differential equations (ODEs). From practical point of view, this model reduction can cause many problems such as in-domain measurement and actuation and control spillover. This thesis attempts to investigate the problem of vibration control of nonclassical microscale beams using the partial differential equation control theory which eliminates spillover instabilities. To this... 

Swarm Robotics consists of homogonous robots with considerable abilities. In recent years, engineering applications, including multi-agent control and air vehicles have been existed and engineers have been interested more in multi-agent systems. Currently, progressive number of studies is being done on decreasing the expenses, developing applicability and compactness of robots. Exchanging some simple robots with a complicated robot results omitting over-complexity and expensive equipments. This project is looking for a method for emerging connectivity and consequently maintaining it for a swarm robotic suffering from limited communication. Limited communication means that agent distinguish... 

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... 

The robots that can move on rough terrains are very important especially in rescue operation, exploration of mine and etc. Since contact surfaces between the robot and the ground are unpredictable, the structure of the robot is usually unintelligible and its motion analysis is difficult. In this research, a ring-like shape robot with flexible body is proposed for motion in rough terrain, gradient paths and passing bars. The ring shape has more usages than other shapes for example as a wheel in a larger robot. Also its flexibility helps the motion particularly on rough terrains. This robot consists of a central section for setting equipments and arms around that. Being radially and... 

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 study, an effective collective control strategy is presented for the decentralized behavior control of a heterogeneous multi–cluster swarm robotic system composed of a group of quadrotors as aerial agents, and a group of two–wheeled mobile robots as ground agents. In this regard, first of all, a new element for swarm robotic systems is introduced. This element, which is made up of a portion of swarm members and encircles the whole swarm, is called the shell element. An algorithm for developing the shell element in swarm robotic systems composed of agents moving in the two–dimensional space is established. Subsequently, inspired by the thermodynamic science and based on the introduced...