Sharif Digital Repository

Microrobots have the potential to access small spaces for manipulation or for acting as a sensor. Magnetic microrobots are the most common types of microrobots. Magnetic microrobots have gained particular traction for medical applications due to safety of tissues. For instance, disease diagnosis, minimally invasive surgery and cell manipulation are potential applications of magnetic microrobots. The performance of a single microrobot could be improved by using multiple robots. For example each microrobot could carry a small payload to a goal inside a microfluidic channel, or could assemble fast and in parallel. In order to employ multiple robots, it is necessary to control each microrobot... 

Magnetic steering of continuum robots is a promising technology that uses a magnetic field to control the robot without contact and can improve the accessibility, safety, and accuracy of the robot. On the other hand, magnetic localization can also be used as a positioning method without direct line of sight in various applications. Common magnetic localization methods face the challenge of dependence on initial guess, divergence, and high computational cost. In this research, by eliminating the unknowns related to the orientation and rewriting the equations, a new method for magnetic localization has been presented. The advantage of the new method in convergence and increasing the speed of... 

In this research dynamic modeling of a 3-DOF (degree of freedom) compliant parallel mechanism with flexible intermediate links has been investigated. Unlike conventional rigid mechanisms that gain their mobility from movable joints, the compliant mechanisms transmit or transform through elastic deformation of flexible members (flexible connector and joint), displacement, force, or energy from input into output. Eliminating clearance, friction, wear and demand of lubrication in compliant mechanisms, and having monolithic structure provides high-precision motion with micro/nanometer level resolution for them. Therefore compliant mechanisms play a significant role in modern technologies such as... 

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,... 

Human walking is widely recognized as one of the most adaptable and robust forms of locomotion in nature, with intricate neural and biomechanical systems interacting to support this complex behavior. It is proposed that these systems are organized in a hierarchical structure, with the lower level comprising a complex distributed system consisting of muscles and the spinal cord, and the higher level being the brain cortex. The higher level is responsible for training and monitoring the output of the lower level, and intervening when the lower system fails to stabilize the system. To control the lower level, one popular model that has emerged is the central pattern generator (CPG). It is... 

Due to the advantages of multi-agent systems, research in this area and the use of these systems in industry are increasingly growing. Applying these robots, various complex tasks can be done faster, safer and with better results. In our country, many different algorithms have been proposed and simulated, but due to the lack of a real environment for implementation, their actual performance has not been assessed. This project aims to create a platform for research and development of this field. This goal is achieved by performing the first phase of implementation, namely the design and construction of the robot platform. In the first step, qualitative and quantitative characteristics of the... 

Control of line of sight (LOS) orientation is a fundamental prerequisite for virtually all dynamic applications in which an optical sensor is used to obtain images. In this research, a 3 DOF parallel mechanism is utilized to build a stable platform for high precision satellite photography. The platform may be designed based on the Stewart platform concept. The stability is obtained by controlling the roll, pitch and yaw of the mechanism. To apply linear control techniques and to use roll-pitch and yaw rates and also their absolute values, an active stable platform is designed. Line Of Sight (LOS) is a position vector from origin of a topocentric-horizontal system to the satellite of... 

The main purpose of the present thesis is to establish a decentralized controller for some car–like multi robots to follow and hunt moving targets. Robots are very similar to actual cars considering geometric dimensions, mass and moment of inertia and so on; and outputs of the controller are steering-wheel and driving-wheel torques appropriately. Dynamics of the moving target is so that it escapes from the robots. Robots are equipped with antenna for getting wireless sensory signals, including range and bearing sensors. Kalman filter is used for estimation the target relative position and speed and robots state variables. The controller is designed for doing the above mentioned group... 

Here, the properties of separability of linkages are studied. In general, a linkage is a simple polygonal chain embedded in 3-space with disjoint, straight-line edges, which are fixed-length bars. The internal vertices are called joints. If the two end points are connected then the linkage is a closed linkage, otherwise it is an open linkage. By imposing restrictions on the way the bars in joints can move, three kinds of linkages as rigid, revolute and flexible can be introduced. A motion in a linkage is the motion of its vertices that preserves the length of the bars, and adheres the restrictions on joints. A collection of linkages are said to be separatable if for any distance d, there is... 

Recent studies show that spherical shape robots have been widely developed by many robotic researchers. A spherical shape can be also benefited in keeping mechanical components and electronic circuits inside a compact volume. The shell can also perform rolling motions for going fast and smooth on flat area. The reconfigurable spherical robot can be configured into a form of two interconnected hemispheres with three legs equipped with three Omni-directional wheels. The conceptual design of the robot will be initially packed and deployed in a spherical configuration. The spherical construction offers ease in transportation and deployment; for example, a number of these robots can be packed and... 

Design and modeling of a micromechanism for generating planar, nano-scaled locomotion is the subject of this thesis. First, we introduced the concepts and fundamental definitions used throughout the thesis. Then, based on the classification of the locomotion principles employed in microrobots, the related literature about design and fabrication of different microrobots is investigated. Inertial slip generation and contact force variation, as the preferred group, is utilized for further analysis. Since friction force is the main propelling source in the microrobot’s locomotion principle, different models proposed for this phenomenon are investigated and the Coulomb friction model is selected... 

One of the most significant aerial vehicles which has been subject of study of so many engineers and students is quadrotor or quadcopter, which is a cross sectional configuration of motors and propellers. This aerial robot is controlled through slight differences between the angular velocities of the four motors, and robot dynamics is completely nonlinear, thus sophisticated control algorithms are needed. The aim of this project consists of design, fabrication and control of a quadrotor capable of stable hovering. First, some preliminary decisions about general charachteristics of the robot were made. According to these decisions, other mechanical parts were designed and fabricated. Then,... 

Underwater robots are broadly used in oceanography to explore ocean environments,inside inspection of pipes, and also to provide security at maritime boundaries. To design an underwater autonomous robot, it is compulsive to take advantage of a high efficient propulsion mechanism to lengthen the tour time span. Since fish-like propulsion mechanisms have presented higher efficiency comparing other mechanisms, they have been paid a lot of attention.In the present research, the hydrodynamic of a thunniform fish robot is analyzed under some reasonable simplifications. Based on the results achieved from this study, closed expressions are developed to predict the steady mean velocity and the... 

Science has been improved in all aspects and robotics is considered an important field, which helps, do work more efficiently. In the meantime, one of the most popular aspects of robotics is the movement, both physical (in terms of the number of mechanical actuators, the number of arms and legs, the number of wheels, the robot's weight and gravity) and in terms of programming and algorithms. Programming and algorithms are divided into two categories: 1. Programs to control robots and manipulate dynamics associated with robot movement. 2. Algorithms and the ways for routing. The first group is programming associated with control of robots. Motion planning or path planning is the next. In... 

In this work inspiring from the nature a control method is proposed for a stable rhythmic walking in a seven-link underactuated biped robot. Stable walking is a very important issue in biped robots and proposing a dynamically stable pattern of motion with the capability of acceleration and learning is our main purpose. It is tried that the presented method make the robot have a human like motion. This method controls dynamically the hybrid model of robot’s movement and stabilizes it by converging the time-invariant constraints considered to make this movement. Moreover, in addition to providing a suitable gait for the bipod robot, a robust control method is designed to improve the ability of... 

In this thesis, the equations of motion of a beam with tip mass on flying support, based on Euler-Bernoulli and Timoshenko beam theories is derived. To attempt for having accurate model in high rotational speeds, stretch variable is considered and employed in the equations of motion. For a planar and a spatial rotating beam, equations of motion are lineralized and simulated. Finite Element Method and Newmark direct integration scheme are employed for the analysis of the governing equations. To support the numerical results, an experimental setup is designed and based on which different tests are performed. A cantilever beam on a flying support free to vibrate in three dimensions is... 

Nowadays, with the remarkable development of the robotics industry, there is an increasing demand for mobile robots. Mobile robots can be deployed individually or in groups for various tasks such as autonomous warehouses, search and rescue operations, firefighting operations, and maintenance and repairs. It is evident that performing certain tasks, such as moving large and long objects or firefighting operations, is more efficient when robots are deployed cooperatively, and in some cases, these tasks cannot be accomplished by a single robot alone. Therefore, in recent years, the issue of path planning for cooperative robots has received significant attention. By cooperation, we mean that... 

The goal of fracture reduction in orthopedic surgery is to reposition the bone fragments in their anatomical orientation (alignment), and the fracture ends closed to each other (apposition). Reduction of long bone fractures is became an interesting subject in the field of robotic aided surgery in pervious decade. Nowadays reduction of femur is carried out by surgeons and medical staff in surgery. Due to the large holding forces necessary, exact positioning is difficult and time consuming. What is needed is an automated system whereby the fractured ends of the bone may be precisely positioned without the need for multiple docking attempts. The fragments need to be held in place as long as... 

A motion tracking control design of an n-DOF rigid robot by taking into account its actuator dynamics is proposed in this paper using backstepping technique. neglecting actuator dynamics in control of rigid robot manipulators can degrade the performance and loss of stability. However,consideration of actuator dynamics entails joint torque or armature currents measurement. In this study, torque measurement has been avoided using an torque estimator.. Finally, Semi-global convergence for motion tracking error are proven. In addition, A simulation example of a two-link robotic manipulator is also given to clarify the effectiveness of proposed design method. Considering actuator dynamics entails... 

Leakages in the transmission pipes include a large proportion of water loss. Scarcity of fresh water in one hand and high costs to compensate for drop in pressure and flow lines, on the other hand, detection and location of leaks have been important. This phenomenon can also cause a lot of damage to the urban contextures. This thesis considers the leakage in tubing buried in the soil by means of a floating robot. Since the rate of leakage, specifies the requirement to perform maintenances, In addition to finding the leakage, an overall estimate of the amount of leakage is desired.Since non-destructive leak detection is desired, the mechanical-magnetic sensor is designed. First, for the...