Sharif Digital Repository

In this research work an analytical instrument has been developed for assessment of energy technologies, R&D resource allocation and technology development. Development of new technologies has been considered according to the specific conditions of developing countries. The analytical instrument includes two models interlinked with each other: energy technology assessment and optimal control of innovation activities. Energy technology assessment and prioritization of new energy technologies are provided by the model of the energy supply system that contains a detailed representation of current and emerging technologies characterized in terms of their technical indices. The results of this... 

Hard disk drives are the main component of computers for permanent data storage. The security of the stored data is related closely to the air gap between the read-write head and the surface of disk. This gap which is created by the aerodynamic force between head and the disk is altered continually by lateral oscillations of disk. In the extreme condition of zero gap and contact between the protective coating layer and subsequently the magnetic material of the disk with the head, the disk will be scratched and damaged. Therefore, the active or passive control of these vibrations has a particular importance in the technology of manufacturing of hard disks. The first step in active control... 

In this thesis, a new approach is proposed for two-level optimal control of large-scale nonlinear systems. In this approach, by defining some parameters as coordination parameters the overall system is decomposed into several interactive subsystems, where the optimization problem redefines for each one of them. The obtained sub-problems which are in the form of standard optimal control problems with lower dimension are solved in the first level. To obtain the overall optimal solution, coordination of the first level solutions is performed in the second level. For solving the first level problems, the indirect gradient and Newton methods are used. The gradient method is applied in the first... 

The collision of moderately large asteroids and comets also referred to as Near-Earth Objects (NEO's) with earth would have catastrophic consequences. Such events have occurred in the past and may occur again in the future. However, for the first time in known history, humanity may have the technology required to counter this threat. Methods studied for mitigation of this hazard are based on deflecting asteroid's trajectory and are normally divided into two basic categories: high energy impulsive methods, and long-duration low-thrust methods. Two parts of mission to be optimized are the trajectory of spacecraft to reach the target and the deflection strategy which could be analyzed by the... 

Increase of sensitive customers to power quality has raised concerns in industries regarding requirements of quality power supply. Uninterruptible Power Supplies (UPSs) are known as efficient tools in providing reliable power supply to sensitive customer. However, in a UPS, getting a desired output requires appropriate structural implementation and successful output voltage control. On the other hand, due to the increase in sensitive loads in customers, the output power range of UPSs has increased. Consequently, design and producing high power UPSs is not economical. In addition, tendency to have high reliability power supplies disrespect of their physical locations has moved researcher... 

In this research a monopolist is considered which its object is maximization of profit during a predetermined period. Optimal control theory is used as a tool for determining of optimal trend for control variables. Price, warranty length and production rate are considered as control variables and cumulative demand and production are considered as state variables. Learning effect in production side and demand side are entered in the model too. In the demand side, learning effect shows its influences with movement of market from diffusion phase to saturation phase. In diffusion phase the demanded quantity of productions increases by increase of cumulative demand, on the contrary in the... 

Low back pain is a common medical problem around the world afflicting 80% of the population some time in their life. Low back injury can result from a loss of torso stability. This investigation seeks to apply existing methods to new applications and to develop new methods to assess spinal stability during its dynamical activities. In this study, firstly, optimization method is utilized as an appropriate explanation of role of nervous system in controlling of spine movements. Spine which is a complex structure of vertebrae and cartilage has been modeled by a 3D inverted pendulum with a ball and socket joint at L5/S1 incorporated with 18 muscle fascicles. Planning of point-to-point spine... 

This study frames optimal policies for determining price , warranty length and Advertisement rate when free replacement of defective items is the business policy and the demand is dependent on price, warranty, advertisement and cumulative sales for high-tech products which have functional aspects. We apply optimal control theory to a profit-maximization model that takes into consideration the expected warranty cost per item. The maximization of market values is based upon a pre-determined life cycle and spans across both expansion and saturation phases of the market. We further investigate the optimal policies for an exponential lifetime distribution, when the demand function is set by... 

A prey-predator fishery model with stage structure for prey is discusing in this thises. The adult preyand predator populations are harvested in the proposed system. The dynamic behavior of the model system is discussed. It is observed that singularity induced bifurcation phenomena is appeared when variation of the economic interest of harvesting is taken into account. We have incorporated state feedback controller to stabilize the model system in the case of positive economic interest. Fishing effort used to harvest the adult prey and predator population is used as a control to develop a dynamic framework to investigate the optimal utilization of the resource. Simulation results show that the... 

In this study, by dividing spine motion in two part, ordinary movement and initial-final accelerated movement, the commands of CNS are evaluated by optimization methods to find synchronous and time varying synergies. Spine, which is a complex structure of vertebrae and cartilage, has been modeled by a 3D inverted pendulum with a ball and socket joint at L4/L5 incorporated with 18 muscle fascicles. Planning of point-to-point spine motion is performed by optimal control method in combined with cost function of kinematics and kinetic features that available in spine structure. In the second step, coactivation of muscles is predicted by utilizing static optimization along with stability... 

In this study, an active control strategy is used for design of passive energy dissipation systems using viscous fluid dampers and structural stiffness modification. The combination of supplemental damping and modification (usually reduction) of stiffness is used to minimize the two main structural response parameters, namely the maximum inter-story drifts and maximum absolute accelerations. In this manner, both structural and nonstructural damages can be controlled.
While active control systems are expected to improve the structural esponse beyond what can be achieved in passive control, the practical implementation of control systems are mostly of passive type.... 

Continuous casting is one of the ingot production methods in which the product has uniform chemical structure, low defects and high production rates. These days, carbon steel and nonferrous alloys are mainly produced by this special method. The design of continuous casting process includes a lot of difficulties due to its technological complexity. One of the most important aspects of this process is the heat transfer during solidification. In the present study, a new mathematical model and its corresponding numerical solution method have been introduced to establish the condition of directional solidification along the major ingot’s axis. The controlling parameters used in the model are... 

We consider the problem of optimal control of switched systems. In order to solve this problem, by using the Lagrange interpolation, we transform it into an equivalent nonlocal optimal control problem, and then by applying several conditions we transform it into a moment problem. This way, a nonlinear and non-convex optimal control problem is converted to an equivalent optimal control problem with linear and convex structure, which allows us to obtain an equivalent convex formulation of the problem. So we obtain an approximation of the unknown function by using the Lagrange interpolation, and an approximation of the integral term by using the trapezoidal method. Finally, we solve the problem... 

In this thesis a novel non-rotating space tethered configuration is introduced which its relative positions are controlled using electromagnetic forces. The attitude dynamics is controlled by three reaction wheels in the body axes. The nonlinear coupled orbital dynamics of a dumbbell tethered satellite formation flight are derived through a constrained Lagrangian approach. These equations are presented in the leader satellite orbital frame. The advantage of using equations in the Cartesian coordinate system over presenting the equations of satellite formation plane angles is the appearance of gravity gradient and Earth’s magnetic field effects. The tether is assumed to be mass-less and... 

This thesis is concerned with an optimal trade-off between communication overhead and the number and size of neighborhoods in a distributed optimal control technique for large-scale systems that is based on the Jacobi iteration and two-layer architecture for communication. Although this method efficiently reduces computational overhead, continuous and proper data transfer between subsystems that are very often far from each other, is required to achieve an acceptable performance. However, limited transmission bandwidth and short communication range result in significant communication overhead. This causes significant time latency between measurement and applied calculated control actions,... 

Many industrial systems have on/off actuators. Traditionally, these systems are controlled using traditional control methods, like PID controller. The performance of this controller is not ideal for these systems, especially in term of transient response and power consumption. Due to the large number of constraints for these systems, to improve the performance of them, it is necessary to use the model predictive control technic. The decision variables of these systems are integer, hence it is necessary to develop the model predictive control method based on integer programming, which is the subject of this thesis. The main challenge in the development of this model predictive control method,... 

The main purpose of this thesis, is the scrutiny of social influences on products sales and prices. That is what probable effects can be imposed on the amount of sale and price of products as a result of customer's satisfaction or dissatisfaction. In this research pricing of a new product is considered which is produced and supplied through market in a monopolized manner for a specific time period. At the first period, people purchase the product given factors such as price, quality, etc. a part of whom, put comments about their experience regarding the product quality on social networks. In following periods, alongside with aforementioned factors, new purchasers also consider positive or... 

As demand for floght has been incrased, a critical questin to pose is that is it economic to use larger Ailplanes or smaller Airplanes with higher flight frequency should be use. It is self evident that in a large Airplane the whole seats can not be accupied in all cases. Conversly, in small Airplanes, in most cases the seats are accupied but for aqual demand there most be more flights.In order to increase the number of flights, new methods should be used in such a way that smaller Airplanes live the Runway as soon as possible.In this project with modelling all effective factor regarding to Landing of a commercial FAR_23 Airplane, the Landing distance and thr erquired time for living the... 

In this dissertation, we propose and analytically investigate a scheme for effective three-dimensional cooling of a nanoparticle optically trapped in a Fabry-Perot cavity using multiple cavity modes. By employing active feedback cooling using amplitude modulation of cavity modes, our approach allows to access the UHV regime without the need for any additional means like an external tweezer or a radio-frequency trapping approach. For a set of feasible experimental parameters, we demonstrate that the cooling rates achievable are sufficient to overcompensate recoil heating. Therefore the approach is suited to trap a particle for indefinite times at UHV pressures, where air damping cannot...