جستجوی مقالات مرتبط با کلیدواژه « UAV » در نشریات گروه « مکانیک »

In this research, one of the widely used control systems of tailless aircraft, named Crow Flap, has been simulated by numerical method and the appropriate opening direction of this system has been investigated. By creating a differential drag on both sides of the aircraft, this system creates the necessary yawing moment and directional control. This system consists of two moving surfaces that are deflected against each other to neutralize each other's force and produce drag. One of the important issues in control systems is the reduction of disturbing moments. Determining the suitable opening direction with the least drag and disturbing moment and increasing the useful moments is the aim of this research. For this purpose, the measurement of these moments and forces are compared in two states of normal and reverse-opening. The UAV under investigation is a lambda-shaped UAV named Swing. Experiments have been carried out at AOAs of 0 to 12° for three opening angles. The created Mesh is unstructured. In this simulation, the continuity, momentum, and scalar equations have been solved by the Simple C algorithm after discretization with the finite volume method, and the turbulence model (K-ω-SST) has also been used. In this research, the opposite opening direction of the Crow Flap, unlike the usual opening direction mentioned in some articles, had a better result, so that at high AOAs, this opening direction has between 5 and 32% less drag and it has produced 10.5 to 35% more Yawing moment along with reducing disturbing moments.

An unmanned aircraft (UAV) is a type of aircraft that operates without the need for a human passenger. These planes are able to fly automatically, without the need for remote control, and are mostly controlled by computers and sensors. UAVs are used in many industries and have various applications, including communications, surveillance, aerial photography and videography, security and border surveillance, search and rescue, scientific and environmental studies, agriculture, as well as the military industry. The advantages of using UAVs include high efficiency, access to difficult and dangerous areas, and cost reduction. However, the use of UAVs also comes with challenges and problems. One of the most important problems is the risk of losing control, aerodynamic problems, and running out of fuel at different angles of attack. Improving aerodynamic coefficients can help increase flight safety and reduce risks related to losing control of the aircraft. In this research, we examine the elements, changing the shapes created on the airplane wing, and applying control surfaces to improve the aerodynamic coefficients.

: In the contemporary landscape, the utilization of multi-rotor drone technology has witnessed a notable upsurge across diverse academic, industrial, and commercial domains. These multifaceted systems have assumed pivotal roles encompassing surveillance, wireless network coverage, remote sensing, search and rescue operations, efficient package delivery, tele-medicine facilitation, security enforcement, monitoring, precision agriculture, traffic management, and infrastructure inspection, among others. The trajectory of technological advancement underscores the impending significance of intelligent quad-copters as a transformative force within the industry, promising to forge novel avenues and redefine conventional paradigms. In effect, this paradigm shift is poised to mitigate operational risks and financial outlays, thereby fostering heightened assimilation of these technological innovations. Projections underscore that drones' market penetration within the civil infrastructure sector is slated to culminate in an approximately $45 billion valuation by end of this decade. This discourse delves into an all-encompassing exploration of the manifold applications and associated challenges intrinsic to multi-rotor systems, with a particular emphasis on quad-copters, across research arenas and diverse industries. Furthermore, the discourse offers an incisive analysis of prevailing trends while shedding light on the contours of forthcoming developments in the utilization of these transformative devices.

This research investigates the effect of fence on wingtip vortices and control surfaces in a bird-like aircraft using numerical methods. In designing and placing the fence, average dimensions extracted from wing root vortices at different angles of attack have been used. In addition, the fence with specified dimensions have been installed at three heights and three different positions along the wing (the length of the winglet is equal to the average length of the vortex in that part, and the height of the winglet is 30% of the diameter of the vortex in that part) and have been examined at angles of attack ranging from 7 to 16 degrees. The next stage of the study is the optimal design of the dimensions of the control surfaces using a single objective optimization method. The aim of this research is to achieve the best possible design that converges to an optimal solution with minimum time and cost. The design of control surfaces is carried out at three points based on the dimensions of the wing root vortex using numerical methods. However, Computational Fluid Dynamics (CFD) analysis requires a lot of computational time.

In a holistic design; Creating a common language between different engineering, taking in to account the designer/customer's interests and preferences, removing potential shortcomings of common design methodologies and taking full advantage of the benefits of MDO approaches are the most important factors for achieving logical and realistic results. In this paper, a novel Comprehensive Preference-based Design approach is presented which attempts to achieve subjective attributes that are defined in the concept of maximization of designer/customer's satisfaction in addition to objective goals which are formulated in the form of minimization of a performance criterion in a two-phase structure using two nested optimizers. In the first phase of CPD, using the concept of satisfaction, the subjective preferences of the designer/customer are defined in terms of fuzzy relationships and operators in the form of demands and desires. Whereas the results of this phase are inaccurate, in the second phase, it is attempted to define a performance criterion and in order to achieve an optimal operational plan, attitude parameters and the compromises needed to meet the designer/customer's preferences are implemented. The methodology is utilized to design of a UAV with flight duration of 24 hours, 45 m/s of cruise speed at least, payload of 200 kg and less than 1 km take-off distance. To evaluate the results of CPD, the design process using MDO in AAO framework is also performed. Comparison of the results shows that despite the higher mass of UAV designed by CPD, overall satisfaction is higher and preferences have been satisfied.

In this research, the split drag system at different AOA for a flying wing aircraft has been simulated and optimized by a numerical method. The split drag system provides vertical axis control by creating asymmetric drag between the right and left wings. The aircraft under study is a lambda shape aircraft with a swept-back angle of 56. The split drag control system is made up of two surfaces on top of each other, by opening in the opposite direction on one side of the aircraft, it creates the drag necessary to produce yawing moment. Their installation position is at the tip of the wings and on the trailing edge. When using split drag, in addition to the yawing moment, a disturbing rolling moment is created, which is caused by the drag difference between the upper and lower surface of this system, and the reason for this is the change in the AOA of the aircraft. Asymmetric opening of the surfaces can reduce the induced roll to zero and in some cases to a minimum. The test was carried out in AOA of 0 to 12ᵒ for drag split opening angles of 10, 20, and 30ᵒ. Calculations based on equations (RANS) are discretized with the finite volume method. The obtained results show how much to add to the angle of the split drag surfaces depending on the AOA in order to find the most optimal mode to neutralize the roll, and finally, the optimized diagrams of this system are obtained.

The growth and use of smartphones have become a pervasive issue in many countries. On the other hand, one of the new and applied technologies that have been able to attract many enthusiasts is the civilian vertical drones or multi-rotors. The diverse and sometimes unique capabilities of flying robots (unmanned aerial vehicles) compared to manned aircraft, along with the much lower operating costs of these devices, have increased the exploitation and development of new applications of flying robots in recent years. One way to develop and implement flying robots for the general public is to reduce the cost of flying robots, making them accessible and easy to use without special training for these devices; The proposed solution for this issue is the development of mobile-based flying robots. ‌‌

Recent developments in control and the use of automatic agents result in attracting attention to the cooperative systems and their abilities in performing efficient missions. Optimal task assignment of multiple cooperative agents is among the most important factors in effective performing of robots and UAVs' cooperative missions. Uncertainty and dynamic conditions are some of the most essential criteria during the simulation of mechanical phenomena.In this paper, the task assignment of a fleet of cooperative heterogeneous UAVs in a dynamic environment including moving targets was examined. An appropriate architecture was applied by using a hierarchical mixed-integer linear programming in order to solve task assignment problems within the reasonable range. To enhance the outlook of solution architecture and therefore achieving some near optimum assignments, a combination of the proposed architecture and a TSK-type Fuzzy inference system was introduced. The results approved a conflict-free and optimal solution in the task assigning problems. Efficiency increase of the proposed innovative architecture in existence of Fuzzy inference systems ranges from 10 to 35 percent. In order to evaluate the proposed approach in experimental and practical terms, a user panel has been designed and used and with the help of this panel, the capability of practical implementation of this approach has been presented.

In recent years, use of non-metric imaging sensors is becoming increasingly common in unmanned vehicles. This can be considered as an alternative to terrestrial mapping. Due to the limitations such as dimension, system weight, and the nature of UAV platform, it is not possible to use high volume and heavy metric sensors. Consequently, most sensors used in UAV platforms are light weight non-metric cameras. Determining the values of the internal parameters of the sensor is important in monitoring the variations of these sensors and improving the triangulation results of these images. Therefore, laboratory geometric calibration for these sensors under similar operating conditions produces better results in later stages. Our station is capable of performing calibration observations and also the calculations of a wide range of non-metric cameras and is currently serving in related organizations with ability to evaluate the accuracy of calibration results.