Sharif Digital Repository

Nowadays, information gathering based on wireless sensor network (WSN) has formed various applications and it also seems to be spreading more in future. Wireless sensor network, is a network composed of multiple nodes, without any infrastructure, each having one or more sensors, wireless communications unit, processing unit, memory, and power supply. Memory capacity, computation power, and power supply are usually considered as valuable resources and limited in nodes. Most of sensor nodes are located in a dense mode and they are susceptible to failure. Therefore network topology may vary dynamically. A sensor network can support real-time communications independent of its type of structure... 

Increasing and diversified use of micro electromechanical components necessitates further development of methods for their secure gripping and transfer. In this research, a piezoelectrically driven microgripper including two gripping sets with four arms has been designed. The system can hold and handle microparts from 100 to 150 microns by applying corresponding voltages between 80 to 20 volts. The design is such that after positioning the work piece between the two microgripper arms the piezoelectric comb-drive actuators are activated. Then the two gripping arms are moved toward each other and ultimately grasp the work piece. In order to determine the behavior of the... 

Nowadays, worm robots are widely designed and manufactured for different applications. The most common applications for these types of robots can be mentioned as maintenance of small pipes and medical purposes in biological vessels such as the lungs, intestines, urethra and blood vessels. The robot must be small, controllable, safe, reliable, energy efficient, and must be able to crawl both, forward and backward. Different worm robots have been developed and manufactured, for different purposes such as, medical and industrial applications. Most of these projects are typically designed with three or more actuators for control of the distance between cells and the clamps.The results of using... 

Oil field industry is one of the most challenging engineering subjects. In oil well drilling, undesired motion could raise a lot of problems such as stuck pipes; wash out pipe, and etc. In this industry, motion prediction is very important because a good prediction can avoid instruments failure and as a result considerable amount of time could be saved. Predicting dynamic characteristics of drill-string such as whirl orbit, whirl speed, and axial, lateral, and torsional displacements, accelerations, and velocities, might be useful in avoiding or decreasing failures. A program based on FEM (Finite Element Method) is developed in MATLAB considering deviation of drill-string, contacting with... 

This thesis is aimed at the modeling and control of atomic force microscope (AFM) in order to improve the scanning speed and achieving video-rate imaging to realize the real-time observation of dynamic phenomena at the nanoscale. The lumped parameter model of the AFM in the non-contact operation mode is studied in this project. The tip-sample interaction is the Van der Waals force, which makes the model nonlinear. Two mathematical models of the AFM cantilever are derived and investigated in order to gain detailed insights into the system dynamics. These models are tip excited and base excited cantilever. The former is solved by the method of multiple scales and the latter is analyzed by the... 

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... 

Delivering high quality and clean air into occupied spaces is the main goal of Heating, Ventilation and Air Conditioning (HVAC) systems. HVAC systems draw supply air which usually contains fungi and moisture. Fungi and moisture plus organic materials create a good bed for mold growth. Studies prove that duct cleaning process can definitely reduce the amount of pollutants present in the ducts. Hence, it has positive impact on human lives both regarding psychological and physical points of view. Duct cleaning method’s application difficulties and ducts’ unreachable environments motivated duct cleaning firms to employ robots for duct cleaning tasks. Although there are considerable numbers of... 

Cooperative systems have been widely studied in literature. The Dual-Arm Cam-Locked (DACL) robot manipulators are reconfigurable arms formed by two parallel cooperative manipulators which operate redundantly but they may lock into each other in specific joints to increase structural stiffness in the cost of losing some degrees of freedom. Obtaining the optimal configuration demands lots of computational time and is not practical in real-time applications. In the present work, considering the kinematics of the manipulator, the optimal control problem of redundancy is formulated in the framework of tasks with the order of priority. The optimal control formulation is derived by using the... 

Herein, an introduction to optimization, aiming to help knowledge development in design optimization techniques is given. Besides, a new method of using the theory of topology optimization to optimize a microgripper system, with a piezoelectric ceramic driver (PZT) microactuator is presented as well. An optimization method is also presented to generate better control conditions. In this study a micro object gripper of 9200 µm length, 8100 µm width, and 500 µm thickness is optimized, and performances improvement is analyzed. This thesis is to investigate best practice and give advice on how to understand the process of topology optimization and how to setup an optimization run. At first, an... 

In the present work, trajectory optimization of the Dual-Arm Cam-Lock robot considering kinematic and dynamic redundancy is performed. First, the optimal control problem is solved only considering kinematic redundancy and then is solved considering dynamic redundancy. General form of the dynamic model for the system is developed using Lagrangian relations. Global optimization method is used for redundancy resolution problem. A performance index is defined based on the consumed kinetic energy and is minimized through a desired trajectory using the global optimization method. Formulations of optimal control problem are derived and initial boundary problem is changed to two point boundary value... 

This thesis describes different neural networks models and an approximation based neural network controller for autonomous underwater vehicles (AUVs). The online multilayer perceptron neural networks (OMLPNN) have been designed to perform modeling of AUVs of which the dynamics are highly nonlinear and time varying. The online recurrent multilayer perceptron neural networks (ORMLPNN) have been additionally designed to generate a memory to pervious states and increase the performance of the modeling. The designed OMLPNN and ORMLPNN with the use of backpropagation learning algorithm have advantages and robustness to model the highly nonlinear functions. The proposed neural networks architecture... 

Advanced Driver Assistance System (ADAS) is a major area of research in today’s vehicle control and safety. In General ADAS can be seen as a mother system with various subsystems to help the driver from pre-crash to post-crash situations. One of the subsystems for ADAS is the Collision Avoidance System (CAS). Nowadays, many researchers are working on different Aspects of CAS, from perception to decision making. Many challenges exist while developing a CAS, but today the greatest challenge is decision making of CAS and its interaction with driver’s behavior. Driving is a complex task and since driver’s consciousness, gender, age and reflexes can cause different behaviors; it is, therefore,... 

Pump operating problems may be either hydraulic or mechanical and there is interdependence between the failure diagnoses of these two categories. Consequently, a correct diagnosis of a pump failure needs to consider many symptoms including hydraulic or mechanical causes. Nonlinear, time-varying behavior, and imprecise measurement information of the systems makes it difficult to deal with pump failures with precise mathematical equations, while human operators with the aid of their practical experience can handle these complex situations, with only a set of imprecise linguistic if-then rules and imprecise system states, but this procedure is time consuming and needs the knowledge of human... 

In this thesis, Optimum Counterweight and Spring Balancing of a novel kind of mechanism called a general 3-RPS parallel robot in Dynamic Motion are investigated. Balancing is explained as the set of configurations on robot inertial and dimensional parameters which, when convinced, certify that the weight of the links produce less force at the actuators for any configuration of the robot, under dynamic or static behaviors. In the references, different procedures have been suggested for balancing that consisted of counterweights, springs, and other auxiliary equipments. Study represents the essential information for having optimum spring and counterweight balancing in a new (3RPS) robot using... 

The investigation of the behavior of structures subjected to various kinds of loadings is of considerable importance. In this research, an attempt was made to analyze behavior of beams that a load is moving on them.Most of the existing relevant works in this field are dealt with examination of elastic beams with constant section, while in most cases beams with variable sections are used in order to have the optimum structure and appropriate stress distribution and to maximize strength to weight or cost ratio. While construct analysis is very advantageous, it is very difficult due to the complexities arising from the variable sections. But this design is so advantageous that it dominates...