نشریه فناوری در مهندسی هوافضا
سال چهارم شماره 2 (پیاپی 13، تابستان 1399)

This paper concerns on guidance law design by considering of the actuator effect. For achieving this goal, the proportional guidance (PN) method would be modified via the back-stepping approach such that the closed-loop stability is guaranteed in the presence of the actuator dynamic. Thus, it is interested to improve the guidance system performance (for example the transient response characteristic and miss-distance error) by the proposed guidance algorithm. Hence, the PN guidance law would be corrected such that the closed-loop system is asymptotically stabilized. The suggested algorithm is numerically simulated in a typical guidance problem. The simulation results verify the effectiveness of the redesigned guidance technique in comparison with the PN method.

Bilevel optimization is proposed when the objective problem has two decision makers with different hierarchies. In such cases, the lower level decision is embedded within the higher-level constraints. Micro and macro decision making of transportation are considered as hierarchal problems, On the one hand, user’s decision tends to choose lower cost, and the other hand is transportation company’s to maximize its benefit. This paper’s aim is to provide a review on research and methods with different concerns for modeling and solving bilevel problems in last three decades. In addition, the latest application of this kind of optimization is presented in aerospace transport issues. This paper also introduces the classic and heuristic algorithms for solving bilevel optimization.

In this paper, the flow field around a two-dimensional rectangular cylinder was numerically simulated and the effects of the flow suction on the separation bubble were investigated. The purpose was to estimate the effect of suction on the dimensions of the separation bubble. The flow field was assumed incompressible, turbulent, and two-dimensional. Gambit software was used for grid generation and FLUENT for numerical simulation.The problem was analyzed in two states: with and without suction, and the effect of suction on the separation bubble was investigated. According to the results, it can be said that the suction length of the separation bubble is smaller, so that in several different cases this length is reduced by about 50%.

This paper is focused on the application of transparent antennas to address the issues related to the unpleasant appearance and non-aerodynamic behavior of traditional antennas. Transparent antennas are divided in two main categories. In the first category, the resonant structure and the ground plane of an antenna, which is usually made of metal, is made of thin film transparent materials or a metallic mesh. In the second category, the structure of a dielectric resonator antenna (DRA), which is made opaque dielectrics, is realized, using a transparent dielectric, such as glass. In this paper, common types of transparent antennas and the methods of realizing each of these antennas are reviewed. The paper also discusses different potential applications of such antennas, especially space applications to save the limited available mass budget in small satellites.

Increasing the rate of drone's usage growth, improvement of infrastructure needed for drone's development by governmental investment, vast and diverse applications and good outcome of the technology depicts special situation for this technology in the future. Moreover, special structural characteristics of this aerial vehicle, cause concern in governments about infrastructure, assets protection, securities and in nations for privacy issues. Governments try to have long term strategical planning to remove obstacles before drones development to make profit from opportunities that drones provide in different area, such as job creation, decrease costs, management of natural disasters, etc.here, After surveying opportunities and challenges of drones development in Iran, solutions to UAV traffic management are reviewed in detail.

Today, all world's aviation organizations, including ICAO, are looking for solutions to airspace shortage, growth of global air traffic, and safety of flights. Performance based navigation (PBN), which is a transition from System-Base to Performance-Base Navigation is a solution that can improve the problems caused by an increase in the number of flights and complexity of air routes. PBN flight plans are implemented through RNP and RNAV. To use these designs, FMS receivers have several input sensors. The most important GNSS input sensor continuously supports PBN operations. However, GNSS services are disable due to atmospheric effects and human-made noise. This paper discusses the opportunities and challenges associated with use of DME as an alternative source for positioning, navigation, and timing (PNT) in the absence of GNSS services.