Sharif Digital Repository

One of the most important issues in medical image processing is the registration of images with various imaging modalities, because in this case, one can take advantage of these imaging modalities and sometimes fuse and use the useful information of each one in the form of a single image.As it was said, MRI and ultrasound images each have their own disadvantages and advantages, and by considering these two modalities, they have tried to integrate the good features of these two. As we know, one of the destructive cases in the MRI image is the inhomogeneity of the image, a inhomogeneity due to the fact that the main magnetic field is not constant and makes the parts of the image brighter or... 

Nowadays, due to the enlargement and complexity of software systems, traditional approaches to software development are not as efficient as before, hence there is a need for new approaches in design, implementation, and maintenance of software systems and processes. Complexity and enlargement of design and initial implementation of systems and processes on one hand, and the requirements appear in the maintenance phase on the other hand, makes the dynamic design of systems and processes a very important issue. However, adding dynamism and changeability to the systems has an upper bound, and additionally, it is impossible to definitely predict trend of systems and processes in the future. This... 

Scene classification is one of the most controversial fields in computer vision. It has many applications such as robot navigation and control, content-based image retrieval (CBIR), semantic organization of image databases, depth estimation and multimedia services. In fact the outcome of any classification system depends on the ability of the feature vector defined for the problem, by means of its distinguishing strength. In this research we focus on efficient feature extraction methods. In recent years, methods based on bags of features and special pyramid approach, have shown good performance in scene classification comparison to the others. So we based our proposed method on these ideas.... 

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...