Sharif Digital Repository

Spinning vehicles are a large category of aerospace vehicles including shoulder launched missiles, intelligent anti-armor projectiles, guided rockets and some of re-entry vehicles, anti tank missiles and satellites. This thesis presents the problems of guidance and control in a spinning vehicle with a single plane of On-Off control surface. The missile uses this single surface to control both yaw and pitch channels. The actuator used in this missile is a discrete On-Off type which makes the missile behavior nonlinear. Using describing function technique, a linear model of the spinning missile dynamics in the presence of an On-Off actuator is derived and a classic controller is designed... 

The problem of launching a satellite to low earth orbit has been considered. Preliminary concepts such as satellite orbits, launcher missiles and their equations of motion, and traditional methods for guidance of launchers are reviewed first. Then a new method for optimizing the launch trajectory under non-ideal conditions is introduced in which the solution of a known ideal trajectory optimization problem is used as an initial guess for the actual optimization problem. Several methods for guiding a launcher to place a satellite in Earth orbit are presented next; they have been titled as (1) launch path re-computation outside the atmosphere, (2) prediction error minimization, and (3) output... 

Many future space missions, will require a high level of autonomy to service, repair, refuel, reconfigure satellites. As we know there is no project that has demonstrated an actual online pathpelanning for a terminal rendezvous phase in docking maneuver, for an uncooperative tumbling target. Particularly when the target is in a noncircular orbit. Such missions require a 6DOF precise position and attitude tracking maneuver that safely can avoid collision to the target and are capable of flying around. This thesis introduce a new guidance method for vectorial approach to the target in terminal rendezvous phase and applies a Sliding Mode method for attitude tracking control with respect to... 

In this thesis, active guidance of a reentry vehicle using fuzzy logic is investigated. The guidance commands of the reentry vehicle (pitch and bank angles) are computed based on estimation of the final conditions, including range and cross-range errors and time-to-go. The final conditions are predicted utilizing a neural network. Inputs of this neural network are the current states of the vehicle and flight time. The first advantage of this approach is that no reference trajectory is required, which is mostly generated optimally for ideal conditions. Moreover, the methods based on keeping the nominal trajectory produce severe guidance commands for sudden disturbances (e.g. wind gusts),... 

Estimation of physical parameters for solutions and mixed liqids are used widely in industrial applications. However, we can do these measurements with conventional laboratory analysis, but we always want to find an easy and quick method that use on-line measurements. In this study electrical properties of different water liquids and mixture samples in frequency stepwise range of 100-100000 Hz are measured by using a short cylindrical capacitive sensor and a measuring module (LCR-703).Operation of the capacitance measurement module for such probes is based on the auto-balancing bridge method.The effects of frequency and volume fraction on the electrical parameters and permittivity of mixed... 

In this thesis, fuzzy logic is used to suggest a simple algorithm in guidance and control suitable for upper stage decoupler transfer with finite and continuous thrust. It is attempted to improve injection accuracy utilizing classic guidance and control methods and fuzzy logic, while unpredictable errors exist. Orbital perturbations, uncertainties in thrust vector, and initial injection errors in parking orbit, are considered in order to actualize results. In this research, Lambert guidance, velocity to be gained, and fuzzy logics are used for upper stage guidance. Fuzzy-PD control is designed and applied into the upper stage. Final results show acceptable position errors and suitable fuel... 

Today, a lot of efforts have been done in order to commercialize space travels. Spacecrafts have a lot of components and producing each of them spends high costs. Components such as propellant tanks and boosters are multi segment and are released simultaneously and therefore it is economically feasible to recover them. Due to Parafoil ability in low-cost, soft (no damage to the cargo) and accurate landing, it is gradually replacing parachute. Parafoil can fly long distances after being released, so its landing point could be determined. The aim of the study is to evaluate this scenario in which some segments of launch vehicle (e.g. booster) that are equipped with Parafoil expand their... 

The purpose of this thesis is sliding mode control of a roll-pitch seeker by considering the zenith pass problem. This problem takes place when the target appears in front of the seeker’s head. First, the mathematical model of the roll and pitch frames is obtained by the Newton-Euler equations of motion. Then, a MIMO sliding mode controller is designed. The performance of the controller is investigated in the presence of model uncertainties and seeker disturbances. The results indicate that the designed controller is robust enough and provides a suitable performance in the stabilization, tracking and guidance loops.
 

Inspection of confined corridors is one of the important and necessary topics in various industries, including mines, oil and gas industries. Human inspection is very time-consuming and expensive due to the difficulty of accessing these environment, and in some corridors, it is not possible to inspect at all. In this thesis, UAV guidance and navigation algorithms have been developed by using informations got from optical flow, inertial and ultrasonic sensors, so that the UAV can fly automatically inside the confined corridor without colliding the boundaries. At first, a model of the space around the corridor, UAV and its subsystems has been proposed so that we can use it to create a...