Sharif Digital Repository

In recent decades, emission from automobiles is considered one of the main reasons for global warming. One of the ways to decrease the fuel consumption of the vehicle, increase the power train efficiency and vehicle acceleration is to use Continuously Variable Transmission (CVT) and infinitely variable transmission (IVT). Previous inquiries include investigate miscellaneous types of continuously variable transmissions and their efficiency and different ways of combination of CVT and other power trains in order to create an IVT. The aim of this research is to optimize one kind of IVT transmission. At first, different state of combination of IVT portions will be investigated. Then, a model is... 

The main purpose of this thesis is to propose effective meta-heuristic algorithms for solving the scheduling problems. We consider the problems that are associated with two areas: project scheduling and shop scheduling. In project scheduling area, only the resource constrained project scheduling problem (RCPSP) is considered. For solving this problem, a hybrid particle swarm optimization (PSO) algorithm is developed. The proposed algorithm outperforms other existing PSO algorithms for the problem. However, most of the contributions of this thesis are related to the second area. The shop scheduling problems of concern include: job shop, stage shop and partial job shop. We developed two... 

This PhD dissertation presents the chemometric techniques as a tool to obtain maximum information from the chemical and biological systems. In this regards, two objectives have been followed. The first objective was to apply the design of experiment methods for approaching the most reliable data. In this section, the main concepts and applications of experimental design approaches to optimize the common analytical chemistry techniques are reviewed. The critical steps and tools for screening including Plackett-Burman, full factorial- and fractional factorial designs and response surface methodology such as central composite, Box-Behnken and Doehlert designs are discussed. Descriptions of... 

Snake-arms are hyper redundant manipulators that have high degree of freedom. Due to their high flexibility they have a great potential to work in the fully restrained, complex and hazardous environments such as Nuclear reactors and space stations. They can also be used for surgery, exploration and rescue. In this thesis the path planning and kinematic control of a special type of snake arm are investigated. In this manipulator, the extra cables are replaced by a locking system to reduce weight of the structure and the number of actuators. Therefore, by releasing and locking the joints in arbitrary sequence and by stretching the cables, the configuration of manipulator will change. This... 

A basic highway design problem is to find the most economical alignment connecting two given end points based on topography, soil conditions, socioeconomic factors and environmental impacts, while satisfying a set of design and operational constraints. The cost function complexity and numerous limitations such as highway design criteria have made this problem a NP-hard one. In this study, a swarm based searching algorithm has been applied to a three dimensional highway alignment optimization model. The spatial data has been exploited from a GIS databases using a heuristic swift approach. In addition, the majority of cost items that depend on highway design have been extended in a practical... 

The aim of this project was to design, analyze and fabricate a 4 DOF robotic arm to be used as a slave robot for tool handling in laparoscopic surgery. The mechanism used for this purpose should have a remote center of motion in order to be able to manipulate the tool through the small incision point. The robot should also provide sufficient force to handle endoscopic tools used for large organ manipulation and be capable of measuring these forces. A variety of mechanisms were studied thoroughly, and the best solution was chosen by considering the design parameters such as workspace, manipulability, accuracy, ease of fabrication, etc. The final design consists of a 2 DOF serial spherical... 

Cable-driven robots are referred to as parallel robots actuated with cables. In fact,in such robots rigid links are replaced by cables, which may be extended to desired lengths without making mechanism much heavy. This robot possesses a number of unique properties that makes it suitable for many industrial applications. The main factor which makes cable robots analysis different from other parallel robots is the incapability of cables to push objects. Hence, obtaining the workspace of a cable robot is one of the most important subjects associated with this type of robot.The goal of this thesis is to design a spatial translational cable driven robot, which may be used for object handling. For... 

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... 

This study strives to minimize a two-criterion objective function of a flexible flow shop scheduling problem with receipt and delivery of jobs in groups and processing them individually. Every group of jobs has a release time, which means that all jobs are not available at the beginning of the planning horizon. Moreover, due to the special characteristics of every job in a group, only a subset of machines at each stage are eligible to process that job. This problem has many applications in production and service industries, such as restaurants and ceramic tile manufacturing companies. The objective function is determined based on the practical applications of the problem. It deals with... 

This research considers the permutation flowshop scheduling problem with sequence‐dependent set‐up times .In this model, every job has a distinct due date and a tardy penalty rate. A mathematical model is developed for the proposed problem. As it has been proved to be strongly NP‐hard, only small‐size problems can be solved with the mathematical approaches. Thus, a meta heuristic algorithm based on the Particles Swarm Optimization (PSO) algorithm is developed to solve the real size problems. Particle swarm optimization (PSO) has been developing rapidly and has been applied, as it is easily understood and realized. Since the PSO algorithm has been introduced for the continuous solution space,... 

There are many exact and comprehensive project management standards that have been presented till now. On the basis of those standards numerous corporations and organizations have collected various methodologies in order to ensure the accuracy of their project management processes. Apart from utilization of a predefined methodology or collecting of a customized one in the organization, there is an important question: in each project what is the suitable project management system (PMS). In this thesis a tool with the help of simulation technique is developed to support the improvement of the organization’s PMS. The processes of a methodology which is on the basis of PMBOK standard are... 

The competition between producers and the contracts issues between the producers and consumers of electrical energy in restructured power systems might cause on unwanted increase in power interchange beyond transmission lines capacity. If the power interchange is not well-managed, it would often cause overloads in specific path. This phenomenon is termed as lines congestion. The major goal of congestion management is to create a set of rules that ensure sufficient control over producers and consumers to maintain an acceptable level of power system security and reliability in the time of limitation of transmission network with maximizing economic market efficiency. As FACTS devices provide... 

In this research, a new metaheuristic algorithm is developed for solving the Discrete Time- Resource Trade off Problem in the field of project scheduling.In this problem ,a project contains activities interrelated by finish-start type precedence constraints and each has a specified work content and can be performed in different combinations of duration and resource requirement.Since the problem is NP-hard , the Particle Swarm Optimization is adopted due to minimization of the makespan subject to precedence relations and a single renewable resource. Basically PSO is used to solve continous problems and discrete problems have just begun to be solved by the discrete PSO.In proposed method,a... 

Planning safe rendezvous and docking trajectories between two spacecrafts has a high importance in the space applications. In order to make two spacecrafts moving in different orbits closer, two stages must be completed simultaneously: First the implementation of rendezvous maneuver which deals with the generation of control/guidance commands leading to trajectories that lead the chaser towards the target. Second the docking maneuver incorporation which makes the two spacecrafts closer with the relative zero attitude. Various approaches have been dealt with till now using the analytical and numerical approaches generally considering rendezvous, not the docking maneuver. These approaches... 

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... 

Hyper-redundant manipulators have large number Degrees of Freedom. Because of their redundancy, such manipulators have the advantage of obstacle avoidance, overcoming singularities and intrusion into highly constrained environments. The most challenging task in designing hyper-redundant manipulators is the synthesis of actuating mechanisms with appropriate kinematics and effective power supply. Most of previous techniques in implementing hyper-redundant robots have the disadvantages of: -Using large number of actuators, -Heavy weight due to large number of actuators, -Complexity of the control system due to need of synchronizing subsets of motors. In this thesis a novel hyper redundant... 

The job shop scheduling problem is an important and applicable optimization problem and has been attracted by many researchers in recent decades. A huge amount of applications of job shop scheduling problem in industries and services has been found yet. During the last decade, the sequence dependent setup time constraint has been considered in many researches, but with respect to the knowledge of authors, very few of these researches have considered the inseparable setup. Furthermore, few of them have considered the release date assumption. In this thesis, the classical job shop scheduling problem and the inseparable sequence dependent setup time and release date constrained problem have... 

Iin this thesis, evaporation of droplets of a spray from a pressure-swirl injector in a sub-atmospheric combustion chamber is studied. The liquid used in this sudy is a hypergolic oxidizer, Dinitrogen Tetroxide, also known as NTO. The significance of this thesis is its application during the cold startup of a satellite thruster when only oxidizer is injected into the combustion chamber. The most important phenomemon in this stage which is also the focal point for this study, is the ‘Flashing’. In this phenomenon a liquid having a temperature above the boiling point of its own species (for the surrounding gas pressure) is present in the solution field. This state is a non-equilibrium state.... 

Reliability and availability are one of the sensitive and significant points in each maintenance system. Due to the nature of bus system failures, that almost consist of large percentage of possibility risk factors is the systems maintenance, in this study for implementing our proposed model, the bus rapid transit garage-line1 were selected. This model is to provide solutions in strategic and operational levels in the network's garage in several sessions. The solutions include decisions about the capacity of human resources in the workshop system, determine the communication policies with suppliers of spare parts and human resources training policies by the standard scoring system, the... 

Due to large range searches (there are various alignments between two points) as well as the complex and non-linear cost functions and a variety of geometric constraints, the problem of optimal railway alignment is known as a difficult problem. For this reason, choosing an alignment between two points is usually done based on a limited number of alignments put forward by experts. In recent years, the study of the railway alignment optimization raised again due to the importance of optimization and introduction of various algorithms and their progress in solving various problems. It is expected that applying metaheuristic optimization algorithms, such as methods based on Swarm intelligence...