فهرست مطالب

Aerospace Science and Technology - Volume:12 Issue: 2, Summer and Autumn 2019

Journal of Aerospace Science and Technology
Volume:12 Issue: 2, Summer and Autumn 2019

  • تاریخ انتشار: 1399/06/26
  • تعداد عناوین: 6
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  • Milad Noorabadi, Rahnama Malihe, Ghasemi Mohammad Amin, Jafar Eskandari Jam * Pages 1-9

    In this paper the energy absorption capacity of stiffened circular composite tube is considered. The governing equations and dynamic equilibrium are first derived and then solved. Additionally, a finite element model of reinforced circular composite tube structure is modeled. At the following, the effects of various parameters such as structural geometry, number of rings and stingers on mechanical behavior of such tubes are considered. The Stiffened cylinder is under axial loading and internal pressure, and boundary conditions for both sides of the cylinder are considered as simple supports. Results show increasing in the amount of energy in the stingers while the number of stingers increases, and decreasing in the amount of total energy while the number of rings and stringers are increase. Total strain energy and the strain energy created in structural elements increase by increasing the ratio of radius to thickness. The analytical solution results are in good compatibility with the results achieved from the finite element method.

    Keywords: Energy, Finite Element, Rings, Stringers, Deflection
  • Ali Khavari, S. Mohammad Reza Moosavi *, Amir Tabatabaee, Shahhosseini Hadi Shahriyar Pages 11-18

    Urban canyon is categorized as hard environment for positioning of a dynamic vehicle due to low number and also bad configuration of in-view satellites. In this paper, a tuning procedure is proposed to adjust the important factors in Kalman Filter (KF) using Genetic Algorithm (GA). The authors tested the algorithm on a dynamic vehicle in an urban canyon with hard condition and compared the results with traditional KF and Weighted Least Square (WLS) methods. The outputs showed that this algorithm could be more reliable more than 114% and 61% against WLS and traditional KF. 

    Keywords: GPS, GLONASS, Urban canyon positioning, Kalman Filter, Weighted least square
  • Ehasan Zibaei, Mohammad-Ali Amiri Atashgah *, Ahmad Kalhor Pages 19-33

    This paper presents a tuned behavior-based guidance algorithm for formation flight of quadrotors. The behavior-based approach provides the basis for the simultaneous realization of different behaviors such as leader following and obstacle avoidance for a group of agents; in our case they are quadcopters. In this paper optimization techniques are utilized to tune the parameters of a behavior-based guidance algorithm; to compromise between safety, trajectory optimality, and control effort during the formation flight. The tuning is formulated as a constraint optimization problem where the penalty function method is used to secure the safe passage of quadrotors around an obstacle. The guidance subsystem is integrated with a consistent dynamic inversion controller to realize a smooth maneuver of the quadrotors along desired trajectories. For more, MATLAB/Simulink is used as the programming platform. The effectiveness of the tuning method is verified, based on the performance of the closed-loop system in the presence of an overall navigation system uncertainties and actuator lags.

    Keywords: Formation flight, Behavior-based Algorithm, obstacle avoidance, Constraint Optimization
  • Alireza Pourmoayed *, Keramat Malekzadeh Fard Pages 35-48

    In this article, the vibrational behavior of a spinning cylindrical thick shell carrying spring- mass systems and conveying viscos fluid flow under various temperature distributions is investigated. This structure rotates about axial direction and the formulations include the coriolis and centrifugal effects. In addition, this system is conveying viscous fluid, and the related force is calculated by modified Navier–Stokes relation considering slip boundary condition and Knudsen number. The modeled cylindrical thick shell, its equations of motion, and boundary conditions are derived by the principle of minimum total potential energy and based on a new three-dimensional refined higher-order theory (RHOST). For the first time in the present study, attached mass-spring systems has been considered in the rotating cylindrical thick shells conveying viscous fluid flow. The accuracy of the presented model is verified with previous studies. The novelty of the current study is consideration of the rotation, various temperature distributions, mass-spring systems and conveying viscous fluid flow implemented on proposed model using RHOST. Generalized differential quadrature method (GDQM) is presented to discretize the model and to approximate the governing equations. In this study the simply supported conditions has been applied to edges and cantilever boundary conditions has been studied in x=0, L. Finally, the effects of the velocity of viscous fluid flow, angular velocity, temperature changes and spring-mass systems on the critical speed, critical velocity, critical temperature and natural frequency of the structure are investigated.

    Keywords: Various temperature distributions, Spring-mass systems, Cantilever cylindrical thick shell, Viscous fluid flow, Spinning
  • Sajjad Hajirezayi, Ali Nouri, Enayatollah Hosseinian * Pages 49-60

    Till now, various models have been proposed in literature to simulate the behavior of riveted structures. In order to find the most accurate analytical method in modeling the dynamic behavior of riveted structures, a comparison study is performed on several of these models, in this research. For this purpose, experimental modal analysis tests are conducted on a riveted plate to verify the efficacy of the analytical models. Moreover, finite element model updating is used to reduce the difference between analytical and experimental results. First, the material properties of plates are optimized using the experimental results obtained from modal tests of a simple plate. Next, the optimization is performed for the physical properties of rivet. At the end, it is concluded that the fastener model proposed by Rutman can bring about the most accurate results when it is used in combination with solid plates and gap elements in the contact region.

    Keywords: Rivet, Riveted Plates, Modal Parameters, Finite element model updating
  • Karim Dastgerdi *, Farshad Pazooki, Jafar Dr. Roshanian Pages 61-70

    airplane in presence of asymmetric left-wing damaged. ‎Variations of the aerodynamic parameters, mass and ‎moments of inertia, and the center of gravity due to ‎damage are all considered in the nonlinear ‎mathematical modeling. The proposed discrete-time ‎nonlinear MRAC algorithm applies the recursive least ‎square (RLS) algorithm as a parameter estimator as ‎well as the error between the real damaged dynamics ‎and a model of nominal undamaged aircraft to ‎generate the desired control commands. The discrete-‎time adaptive control algorithm is augmented with a ‎Nonlinear Dynamic Inversion (NDI) control strategy ‎and is implemented on the NASA generic transport ‎model (GTM) airplane while considering the effect of ‎wing damage and un-modeled actuator dynamics. The ‎stability of the proposed nonlinear adaptive controller is ‎demonstrated through Popov’s hyperstability theory. ‎Simulation results of the introduced controller are ‎compared with the classical discrete-time adaptive ‎control strategy. The results demonstrate the effective ‎performance of the proposed algorithm in controlling ‎the airplane in presence of abrupt asymmetric damage.‎

    Keywords: Flight Dynamics, Nonlinear dynamic inversion, tip-wing losing