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... 

Designing Nonautonomous periodic systems such as helicopters, multirotors, monocopters or the dynamics of flapping wings requires stability analysis and careful examination in order to identify and determine their dynamic behaviour. In practice, analysis and design are interdependent and the design of nonlinear control systems involves an iterative process. To know the importance of identifying and to accurately implement methods to analyse this kind of systems in the field of aerospace, the flapping wing can be a good example. The issue of stability and the control of the flapping wings have not yet had a clear solution, and the current research including controller design based on linear... 

The purpose of this research is the conceptual design of an aerial robot that has the ability to reach different locations without changing its horizontal attitude. The main missions of the aerial robots are monitoring and delivery, in which none of them requires the robot to leave its horizontal attitude. The main task of the robot is to deliver the goods to the specified points. In order to do this, it must have an appropriate container for carrying the cargo, high safety to prevent damage to the cargo and individuals, the ability to carry out missions when one of the subsystems exits, and the appropriate flight speed for Deliver cargo to the customer as fast as possible. All of the... 

A comprehensive adaptive flight control system in the presence of internal and external disturbances is introduced in this dissertation. In this regard, two different approaches, namely, a centralized model and a multi-model structure are developed using the capabilities of neuro-fuzzy systems in order to identify the dynamic model of an air vehicle after the fault occurrence in the simultaneous presence of model uncertainties and external disturbances. Subsequently, a Model Predictive Control (MPC) approach is designed for the identified model, which can satisfactorily deal with nonlinear and multi-variable nature of the system. In addition, system constraints can be effectively considered... 

Dynamical behavior of a dragonfly-like with rigid flapping wings considering aerodynamic forces has been modelled and simulated. At first, the dragonfly with its unique flying capabilities and the reasons for choosing it has been introduced. Then, modelling process is started with preliminary definitions including frames, coordinates and equations of motion, continued by applying initial conditions and ended with verification tests. After that, aerodynamic effects in a quasi-steady sense is added to dynamical model resulting in an 18 DOF model developed to be used for nonlinear simulation or controller designing. At the end, the results are validated in comparison to an experimental study.... 

In this research, first the use of an aerial system for the inspection of industrial chimneys has been investigated. Then, a series of typical requirements are set for the mission of the flying vehicle, and then a suitable multi-rotor for inspection of industrial chimneys has been designed. After determining the aircraft, among the large number of controllers that have been implemented on the multi-rotors since 2008 , the ADRC controller is selected and based on it a control system for the aircraft has been designed. Finally, this controller is tested in 5 different scenarios to evaluate and show its performance and robustness  

In this study, the nonlinear modeling of insect-like flapping-wing was investigated as a multi-body system using the Newton-Euler method. This modeling, in addition to aerodynamic effects, has specifically addressed the effect of mass and inertia of the wings in the equations on the dynamics of the system. Then, by transforming the equations into a state-space form, a model reference adaptive controller was designed with Lyapunov stability proof. This controller enables optimal control performance in the face of variations caused by the uncertainty of the flapping-wing parameters, considering the fast dynamics of the control actuators and introducing an optimally linearized reference system.... 

This study focuses on path planning for a team of Unmanned Aerial Vehicles (UAVs) involved in efficiently searching a region for early wildfire detection. The primary goal of the path planning algorithm is to identify optimized search paths that maximize the likelihood of detecting wildfires. This optimization considers various factors, including UAV flight time constraints and the locations of the final bases. To improve the algorithm's performance, an initial phase incorporates the utilization of density-based clustering to eliminate noise within the probability map. Furthermore, centroid-based clustering is applied to mitigate the complexity of the optimization problem. Subsequently, an... 

Classical methods in aircraft conceptual aircraft design have some deficiencies in such as low accuracy in aerodynamic derivatives estimation and incapability of verifying flight handling quality. Moreover, application of experimental equations and dependence on statistical data are other drawbacks of classical methods which are accounted as big challenges in development of unusual aircrafts. In this research, a comprehensive, rapid and practical software is developed in order to promote the conceptual aircraft design. This software provides a platform to perform various tasks such as aerodynamic measurement, nonlinear simulation, system identification and optimization simultaneously. In... 

The aim of this study is to develop a new algorithm to perform high performance and precise maneuvers for variety of fixed-wing UAVs. Iterative learning in conjunction with an adaptive control technique is developed here for this purpose. In this research, the guidance and control laws are initially developed by classic algorithms that exist in most of commercial autopilot systems. Then, the learning algorithm is combined with the classic autopilot system to improve trajectory tracking performance. The algorithms have been tested by simulation in the loop technique, utilizing Simulink and X-Plane software. So, the navigation data was provided by the X-Plane, solving dynamic equations, and... 

In this study, in order to enhance the accuracy of tracking repetitive maneuvers in Unmanned Aerial Vehicles (UAVs), an educable control scheme is proposed. At the outset, the controller is designed based on the sliding mode control (SMC) technique. In addition, the offline PD-type memory-based iterative learning control (ILC) is used along with SMC. In ILC scheme, the error of states is saved during the maneuvers that will be used in the subsequent iteration. Also, in order to increase flexibility of the new control structure, ILC-SMC, a multilayer perceptron has been developed. This network is designed to extend the control signal, generated by ILC, to similar maneuvers. The presented... 

In this thesis, a framework for measuring the relative dynamic similarity and multi-fidelity design of the dynamic similar model of aircraft is presented. The conditions for establishing dynamic similarity between the scaled model and the original aircraft have been investigated for different applications and the methods for establishing relative dynamic similarity have been studied. In related researches conducted in the field of designing similar dynamic models of flying devices, the degree of relative similarity has not been measured and usually one or more scaling laws have been omitted according to the type of application. In this thesis, it has been shown that partial dynamic...