نشریه مهندسی هوانوردی
سال بیست و دوم شماره 1 (بهار و تابستان 1399)

In this paper, a new approach to fault detection and isolation for multiple simultaneous faults for a quad-rotor system is proposed. This method is based on parity space and high accuracy diagnosis of multiple faults can be achieved with the proposed method. Another advantage of this scheme is that in addition of its fault localization capability, types of faults could be identified as well. In this research only multiplicative actuator faults is considered and step, impulse and sinusoidal fault are studied. To achieve high accuracy, 10 residuals are generated and multiple combination of these residuals are studied for diagnosis purposes.  As the parity space approach is used only for linear systems, linear dynamics of quad-rotor in hovering mode is selected for simulations. Simulation results show the effectiveness and high accuracy of the proposed method in both fault detection and diagnosis and type identification of actuator faults.

In this research, the design, fabrication, and aerodynamic analysis of a small remote-controlled airship are investigated. The airship must be capable of carrying a 2kg payload. In this research, the design of various parts of an airship such as envelope, gondola and tail has been investigated by using theoretical and empirical formulas. To check the accuracy of the design, digital datcom software was used to perform an analytical analysis as well as the fluent software to numerically evaluate the flow around the airship and calculate the forces and moments applied to it. The investigations were carried out at a free stream speed 15m / s and in the various angles of attack from -10 ° to 10 °. In the numerical study with fluent software, the unstructured grid and the   turbulence model were used. The results showed that the airship was well modeled in digital Datcom software. Also, at low angles of attack, the good agreement between fluent's data and digital Datcom's data is observed. Digital Datcom's data can be used to obtain aerodynamic coefficients during the design phase. At all angles of attack, the airship has static stability and at low angles of attack, it has the least stability and maximum maneuverability. The drag coefficient obtained from Digital Datcom has a significant difference with the Fluent and other references data. therefore, Digital Datcom cannot be predicted at design phases for the drag coefficient.

The twist is one of the most important parameters in the design of the flying wing and tailless aircraft that causes eliminate some aerodynamic challenge at these categories of aircrafts. The present study was performed for an aerodynamic investigation of the geometrical twist at a subsonic flying wing and evaluate this parameter at different flight phases. The study geometry is a lambda-shaped flying wing that has a wing with a 56-degree sweepback. The twist angle applied on wingtips is washout, which is linearly distributed along the wingspan. The study is conducted in the framework of numerical simulation and based on solving Reynolds-Averaged Navier-Stokes (RANS) equations by finite volume method. The simulation process was performed after validation with experimental data, for twist angles of 0 and 6 degrees and range of attack angles of 5 to 20 degrees; also, to investigate the twist performance in the range of landing and take-off phase and cruise phase, studies have been performed in two different Reynolds numbers. The results show that by applying twist, the aerodynamic efficiency is improved at high angles of attack, but this characteristic will drop significantly at the zero-degree angle of attack. Also, by applying the twist, the conditions required for longitudinal stability are satisfied, and the pitch up phenomenon will be delayed.As speed increases, aerodynamic efficiency improves over a wide range of attack angles; also, aerodynamic efficiency changes due to twist increased, and twist will be more effective. Pitch moment analysis shows that as speed increment, the degree of stability will increase, and the pitch-up behavior will improve.

In this paper, the problem of guidance in the mid-course of a projectile’s flight has been addressed to meet the requirements and limitations of the homing phase. These requirements and constraints are usually for low cost systems that are required to increase their range, including the angle of priority (angle of view) and the flight path angle (the angle of impact) of the projectile along with the amount of control effort obtained in the mid-course. Obviously, if these requirements are met, the success of the projectile mission will increase. Therefore, considering the importance of the problem and despite the various and scattered works that have been done so far, in this research, first the mid-course guidance optimization problem of the projectile based on a performance function consisting of the control effort criterion, and also the final values ​​of view angle and flight angle in the mid-course is defined as the penalty functions, respectively. Then, using the particle swarm optimization algorithm, optimal acceleration commands are generated. The simulation results compared with other methods show the proper functioning of the algorithm and its ability to solve more complex models.

Corrosion is a harmful phenomenon for metals have been utilized in various industries like aerospace. Uniform, galvanic, pitting, intergranular, and crevice corrosions are types of corrosion causing approximately 20% of the whole repairing costs of aircraft. The flying condition alters during the flight results in enormous problems for an aircraft. Several methods have been reported to diminish the corrosion rate in which the protective coatings have been exploited in this assessment. To this end, three-layer coating employed to apply on the steel and aluminum substrates. Middle layer and top coat were similar relating to high-build epoxy and polyurethane, respectively. However, zinc-rich epoxy was applied on the steel substrate and neat epoxy was employed for aluminum for the primer layer. The airless spray was used to fabricate different coating determining 6-24 h for curing of each layer. EIS results illustrated that this coating protective system showed just one-time frequency response after 1000 h immersion in 3.5% NaCl exhibiting the fact that water molecules could not penetrate through the coating and access the substrate after 1000 h. Additionally, the low-frequency response of EIS plots confirmed the excellent anti-corrosive performance of coating system applied on the aluminum. Moreover, the pull-off test clarified the reasonable adhesion strength of the coating system on both aluminum and steel substrates.

The main purpose of this study is to design a microblowing system to reduce the drag force of an aircraft with SC(2)-0710 supercritical airfoil. For this purpose, the subsonic turbulent flow around the airfoil is simulated by the Fluent software. The numerical simulation has been investigated in cruise conditions at the Mach number of 0.4-0.6 and attack angle of 0º-3º. The turbulent flow is simulated using the SST k-ω turbulent model, and the UDF code is written in C programming language to apply the microblowing technique. The numerical results have been compared with the available experimental and numerical data, and they have had in accordance with each other. The results showed that the friction drag coefficient decreases with increasing the blowing fraction. On the other hand, in attack angle of 0º-2º, the increase in blowing fraction causes to increase the pressure drag coefficient of the airfoil with its microblowing compared to the airfoil without it. In fact, the microblowing has created the reverse effect on the pressure field around the airfoil. The results have been examined for six microblowing positions. It was detected that the greatest reduction in the total drag coefficient has occurred when microblowing has been located near the leading edge on the suction side. Also, it was observed that the lift force decreases by applying the microblowing, but the selected position has the least effect on reducing the lift coefficient. Besides, the results showed that the suitable results (that is, the lowest drag force) have been attained at the attack angle of 3º. Finally, after the numerical studies, the proposed system is designed, and assembly and disassembly maps have been provided.