@article { author = {Dr. Pourtakdoust, Seid H.}, title = {A Modified Midcourse Guidance Law Based on Genelarized Collision Course}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {3}, pages = {113-123}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {}, keywords = {}, url = {https://jast.ias.ir/article_51517.html}, eprint = {https://jast.ias.ir/article_51517_6dbcd8c9eca84a2b54920502cc652966.pdf} } @article { author = {saghafi, fariborz}, title = {In-Trim Flight Investigations of a Conceptual Fluidic Thrust-Vectored Unmanned Tail-Sitter Aircraft}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {3}, pages = {125-133}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {The feasibility of using a stand alone Fluidic Thrust-Vectoring (FTV) system for the purpose of longitudinal trim of an unmanned aerial vehicle is the focus of the research presented in this paper. Since the fluidic thrust vectoring requires high pressure secondary air to deflect the engine exhaust gases, this research also provides an analytical toolset for preliminary sizing of a suitable secondary air supply. The study is based on a conceptual model of a VTOL tail-sitter type unmanned aerial vehicle in three common phases of flight named as Hovering, Transition and Cruise. A relationship is finally presented between the thrust-vectoring angle and the required secondary mass flow rate. It is found that the aircraft trim is possible only by using fluidic thrust-vectoring. In addition, the mathematical model developed in this study can be used as a preliminary tool for overall performance evaluation of such a conceptual aircraft, especially for sensitivity analysis of thrust-vectoring control and finding the optimum values of the parameters like centre of gravity and engine location.}, keywords = {Fluidic Thrust Vectoring (FTV),VTOL UAV,Tail-sitter Aircraft,Transition Flight}, url = {https://jast.ias.ir/article_51518.html}, eprint = {https://jast.ias.ir/article_51518_8fce644cb890c3949d1bbd86ded71f1f.pdf} } @article { author = {Dr. Moosavian, Aliakbar}, title = {COMPARISON BETWEEN MINIMUM AND NEAR MINIMUM TIME OPTIMAL CONTROL OF A FLEXIBLE SLEWING SPACECRAFT}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {3}, pages = {135-142}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {In this paper, a minimum and near-minimum time optimal control laws are developed and compared for a rigid space platform with flexible links during an orientating maneuver with large angle of rotation. The control commands are considered as typical bang-bang with multiple symmetrical switches, the time optimal control solution for the rigid-body mode is obtained as a bang-bang function and applied to the flexible system after smoothening the control inputs to avoid stimulation of the flexible modes. This will also reflect practical limitations in exerting bang-bang actuator forces/torques, due to delays and non-zero time constants of existing actuation elements. The smoothness of the input command is obtained by reshaping its profile based on consideration of additional derivative constraints. the optimal control problem is converted into parameter optimization problem. The steps of the solution procedure and numerical algorithm to obtain the time optimal control input are discussed next. The developed control law is applied on a given satellite during a slewing maneuver, and the simulation results show that the control input with just few switching times can significantly lessen the vibrating motion of the flexible appendage, which reveals the merits of the developed control law. the modified realistic optimal input compared to the bang-bang solution goes well with the practical limitations and also alleviates the vibrating motion of the flexible appendage, which reveals the merits of the new developed control law.}, keywords = {}, url = {https://jast.ias.ir/article_51519.html}, eprint = {https://jast.ias.ir/article_51519_1db490f258fed4e600b7f5b6e155fdf9.pdf} } @article { author = {}, title = {Robust Integral Sliding-Mode Control of an Aerospace Launch Vehicle}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {3}, pages = {143-149}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {An analysis of on-line autonomous robust tracking controller based on variable structure control is presented for an aerospace launch vehicle. Decentralized sliding-mode controller is designed to achieve the decoupled asymptotic tracking of guidance commands upon plant uncertainties and external disturbances. Development and application of the controller for an aerospace launch vehicle during atmospheric flight in an experimental setting is presented to illustrate the performance of the control algorithm against wind gust and internal dynamics variations. The proposed sliding mode control is compared to non-linear and time-varying gain scheduled autopilot and its superior performance is illustrated by simulation results. Furthermore, the proposed sliding-mode controller is convenient for implementation.}, keywords = {Launch vehicle control,Robust Control,Variable structure,Autopilot}, url = {https://jast.ias.ir/article_51520.html}, eprint = {https://jast.ias.ir/article_51520_4d7fb000e82cf417f2dc18426f7f767d.pdf} } @article { author = {Dr. Sedaghat, Ahmad}, title = {NORMAL FORM SOLUTION OF REDUCED ORDER OSCILLATING SYSTEMS}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {3}, pages = {153-158}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {This paper describes a preliminary investigation into the use of normal form theory for modelling large non-linear dynamical systems. Limit cycle oscillations are determined for simple two-degree-of-freedom double pendulum systems. The double pendulum system is reduced into its centre manifold before computing normal forms. Normal forms are obtained using a period averaging method which is applicable to non-autonomous systems, more advantageous than the classical methods. Good agreement is observed between the predicted results from the normal form theory and numerical simulations of the original system.}, keywords = {}, url = {https://jast.ias.ir/article_51521.html}, eprint = {https://jast.ias.ir/article_51521_58aab625c875846934d932b76b58fd3d.pdf} } @article { author = {Parhizkar, Hamid and Karimian, Seyed Mohamm}, title = {Laminar and Turbulent Aeroheating Predictions around Multi -Cone Configurations in Hypersonic Equilibrium - Air Flow}, journal = {Journal of Aerospace Science and Technology}, volume = {3}, number = {3}, pages = {159-166}, year = {2006}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {}, keywords = {}, url = {https://jast.ias.ir/article_51522.html}, eprint = {https://jast.ias.ir/article_51522_8ec0b8596e9c671d007149b180442397.pdf} }