نشریه فناوری در مهندسی هوافضا
سال هفتم شماره 4 (پیاپی 27، زمستان 1402)

According to friction stir processing For production of surface composites with constant progress and rotational speed, samples are made in different number of passes (1,3.5) and to obtain the stress range and adjust the device and apply the fatigue and tensile test is performed. Results of micro-structure study showed that with increasing number of passes, the distribution of underlying particles is improved, and maximum yield strength is for one sample and three samples have the longest Hight cycle life fatigue. The goal is improve the metal micro-structure with the new friction stirring technique, result shown the strength of the metal is improved, and resistance to wear, fatigue and corrosion is increased, it causes improvement of form-ability, which results increase in the number of The pass has led to a homogeneous and uniform distribution of reinforcing particles, in fact, increasing the number of passes in the process has led to a better distribution and separation of silicon-carbide particles in ground phase.

This article aims to control the group flight of unmanned helicopters. After presenting the dynamic equations using the Newton-Euler method, the dynamic inversion control has been applied to control the position and attitude of helicopters. generalized predictive control was also used to control the position and attitude of the helicopter. And the results of the simulation of these two controllers were compared, which showed the better performance of the predictive control. Therefore, in the design of the formation control, the independent control of the helicopters was done using the predictive control method. To control the formation, the method based on the leader-follower model has been used, An integral sliding mode controller is also used to control the dynamics of the formation error. The results of the simulation showed the success of the tracking by increasing the number of helicopters and the linear and spiral paths in the control commands.

n this paper, the use of PID controller to control a model of a quadrotor with nonlinear dynamics is investigated. In this regard, after presenting the designed nonlinear dynamic quadrotor model, four distinct methods for adjusting the parameters of this controller are examined and compared. These four techniques, which are classified into two categories, online and offline, include online techniques of neural network and fuzzy inference, and offline techniques of genetic and particle swarm optimization algorithms. Finally according to the results of numerical simulations and the results of comparing a predefined squared cost function calculated in each case, in the presence of a relatively large disturbance with amplitude and frequency that is selected in the whole time simulation affects the system, shown in general, the order online algorithms, especially despite the mentioned disturbance, have better performance in controlling the dynamics of the system because they update the control coefficients of the closed-loop system momentarily in each step of numerical simulation.

In this research, by improving the accuracy of existing high-order theories, a new corrected high-order composite cylindrical shell theory with twelve displacement components has been developed. In this theory, the effect of terms related to the trapezoidal shape of the shell cross-section (1+z/R) in the results of the shell stress has been accurately calculated. After adding the strain energy such as the initial stresses and the strain energy such as the prevention of the rotation of the rigid body to the shell energy functional, based on Hamilton's principle, the equilibrium equations of the cylindrical shell with two ends have been derived. By using these equations, eigenvalue analysis (free vibrations) have been performed. Validation of the results of the present research was done by comparing with the theoretical and experimental results of other researchers and the results of the ABAQUS software, and a good match has been achieved.

Light is as an environmental factor affecting plant growth. So far, various light sources have been used to grow plants in closed systems and space studies. Traditional light sources have some problems and are not suitable for space research. The biggest problem of them is the need for the high energy source, power supply weight, and heat production. LED light spectra were designed to solve plant cultivation problems in space for the first time and are recently used in terrestrial research such as greenhouses and plant cultivation rooms. The LED spectra have different colors, but laboratory studies are needed to determine the plants' involvement for these spectra. In this study, LED light technology, effect of spectra on the growth, production of metabolites and optical receptors are investigated.

Supplying the energy demanded by spacecraft and satellites is an ever-increasing need. As a result, it is an active field in developing space technologies. In addition to the commonly used rigid substrate solar arrays, flexible substrate and concentrator solar arrays are other available categories. This paper reviewed the developments and commercial technologies in each category. The flexible solar arrays, implemented in several spacecraft during the last two decades, have recently attracted attention in satellites. It seems that these arrays will replace rigid arrays in the near term due to their higher specific power and smaller stow volume than rigid arrays.