Sharif Digital Repository

Ducted fan vertical take-off and landing (VTOL) aerial vehicles have drawn many attentions in the world because of their capability to offer high power to weight ratio for a certain vehicle diameter relative to open rotors or helicopters. However, due to inherent uncertainties in dynamics and inefficient and poor quality responses, significant control challenges are still unsolved and exciting fields for research. In the current study, a nonlinear dynamic model is proposed for the controller design purpose. This model is validated against simulation by performing several standard scenarios. An adaptive control method, named model reference (MRAC), is utilized to design a perfect controller... 

In this work, A new hybrid approach is presented to optimize a trajectory of Micromechanical Flying Insect in an obstacle reach environment. Here, a singleobjective Evolutionary Algorithm is utilize for finding solutions corresponding to multiple conflicting goals, which include minimizing the length of the path while maximizing safety margin by avoiding hard and non-moving obstacles. On the other hand, dynamic constraints of Micromechanical Insect such as maximum and minimum attitude angles and speed should be taken into account. In order to reduce the computational cost, a novel hybrid two-layer procedure is suggested for trajectory optimization. In the first layer, the algorithm generates... 

Identification of dynamic behavior and extraction of mathematical model for aerial vehicle is important in design, test and evaluation processes. Due to explosion of unmanned vehicles industry in recent years, many innovative aerial concepts is introduced. Coanda-effect air vehicle is one of these novel ideas which is similar to flying saucers. In this study, an experimental scale model of this air vehicle is designed, built and tested with purpose of identifying the linear dynamic model of the vehicle, using the frequency domain identification methods. Performing the system Identification in hover requires a stable hovering capability in the vehicle. Given the inherent instabilities of... 

In every modern society, the engineers and technical managers are in charge of planning, designing, manufacturing and utilizing the simplest products to the most complex systems. This shows the importance of reliability management in engineering systems. Inattention to the reliability of such systems leads to the difficulty or even impossibility in planning or utilizing them. Malfunction of products and systems results in disruption in different levels and can be regarded as a severe threat to society and environment.
Therefore, consumers and general public expect products and systems to be durable, reliable and safe. Thus, the main question is how safe and how reliable the system will... 

In this thesis, dynamics of a turbojet’s fuel control unit is studied for the nature and the range of its inputs and outputs. Then, inputs and outputs involved in the system identification process are determined. Tools needed for the application of the input and the signal data sampling are recognized, and henceforth, with the appropriate input applied and the frequency-domain system identification process carried out, desired linear transformation functions representing dynamics of the fuel control unit are found. Using these transformation functions, the fuel control unit is simulated to be converted to an electronic control unit  

In this study, adaptive control of attitude and position of a rigid body insect-like flapping wing is investigated. For this purpose, a non-linear dynamic and time varying modeling and simulation is carried out initially with six degrees of freedom, and then the accuracy of the simulation is evaluated during different test cases. In order to design the controller, non-linear and time varying dynamic is transformed into non-linear and time-invariant dynamic using theory of averaging. Then, a non-linear controller is designed based on Lyapunov stability theory. Due to the inefficiency of the aforementioned controller under disturbances and unknown uncertainties in the model, an adaptive... 

The formation flight of satellites corresponds to a group of small satellites, performing the mission of a presumed larger and more expensive satellite. Usually mission designers tend to put these satellites in such orbital configurations that their trajectories do not intersect. Although a stable configuration in a certain collision-free orbit is desirable for long term purposes, most of the missions including maneuvers like forming or changing a configuration and inserting new satellites need to be planned using a proper path planning algorithm. In this thesis, a path planning algorithm is suggested that acquires the optimal and impact-free trajectories for a group of satellites for... 

In this thesis the problem of path planning for aerial robots,specifically the UAVs, is studied. Some software packs aiming to perform optimal path planning are already published worldwide. In this thesis, these software are investigated and UAV path planning is done by them. In UAV path planning using these software, due to the high number of equations, number of constraints in solution increases and even in a simple problem, the process of solving becomes difficult for software. Among introduced software packs, “GPOPS”, which uses pseudospectral methods, is chosen as the best. Avoiding obstacles in different problems is checked. Obstacle avoidance and waypoint tracking at the same time,... 

In this thesis, LMS, NLMS, RLS, ADALINE and ANFIS as five adaptive noise removal methods have been studied with a software application approach. The aim of this study is to obtain the best method to remove noise in terms of signal to noise ratio (SNR) improvement as well as the speed of convergence. In this regard, firstly by applying a frequency sweep input, which is contaminated with white noise, the performance of these algorithms are investigated. Then, an audio signal is utilized as the target input, and the performance of the corresponding algorithms have been analyzed in aspect of filter order and learning coefficient. The results show that by increasing the order of filter and...