Hasil untuk "Motor vehicles. Aeronautics. Astronautics"

Zetian Zhang, Min Gao, Dan Fang et al.

Aiming at the optimization problem of multiloitering munitions cooperatively surrounding moving targets, this paper proposes a cooperative surrounding and attack method based on the wolf pack algorithm (WPA). Firstly, the relative kinematics model between the munitions and the target is established, and the cooperative surrounding task flow is analyzed in detail. Secondly, leveraging the “wandering–summoning–besieging” mechanism of the WPA, a comprehensive fitness function incorporating multiple constraints is designed, including favorable attack radius, attack angle constraint, surrounding area constraint, intermunition collision avoidance, and desired surrounding points. This method utilizes the WPA to distributively solve for the optimal control command in each decision cycle, guiding the munition cluster to maneuver cooperatively and achieve an even distribution around the target. Simulation results demonstrate that compared with other swarm intelligence algorithms such as particle swarm optimization (PSO), grey wolf optimizer (GWO), and sparrow search algorithm (SSA), the proposed method exhibits superior performance in terms of convergence speed, solution accuracy (fitness value), and computational efficiency (CPU time). It effectively achieves cooperative surrounding and attack against both single and multiple targets, significantly enhancing combat effectiveness and providing a novel solution for the cooperative decision-making of intelligent munition clusters.

Guy Maalouf, Thomas Stuart Richardson, David Roy Guerin et al.

Safe Beyond Visual Line of Sight (BVLOS) operations are increasingly required for wildlife monitoring and conservation, yet existing regulatory frameworks are rarely tailored to protected areas characterised by low population density and limited infrastructure. This paper presents a field-based use case illustrating how the Specific Operations Risk Assessment (SORA) methodology can be applied to conservation-oriented BVLOS missions under Kenyan airspace conditions, including coordination within military-controlled airspace. We evaluate three population-density estimation approaches (qualitative, bottom-up, and top-down) against available ground truth, and compare tabulated and analytical SORA methods for deriving the Ground Risk Class. The work illustrates how SORA 2.5 structures ground and air risk reasoning in a conservation context, while retrospective review identifies limitations in containment, Operational Safety Objectives, and tactical mitigation performance requirements. Field trials involved five concurrent teams and 30 personnel conducting over 260 flights and more than 60 h of UAS activity across the Ol Pejeta Conservancy, providing insights into multi-team coordination under field conditions. Field implementation revealed areas of misalignment between prescribed safety requirements and operational realities, prompting iterative adaptation of workflows and procedures. Observed outcomes included reductions in team size (25–50%) and procedural steps (18%), derived from retrospective comparison of field procedures. A lightweight Uncrewed Traffic Management prototype was also trialled, revealing practical limitations in conservancy environments. Finally, we present a ten-step framework for developing field-ready safety procedures to support risk-informed decision-making in non-standard operational contexts. The findings provide empirically grounded guidance on applying SORA principles to conservation UAS missions, without proposing a new risk framework or generalised operational model.

Haixia Chen, Zhixin Liu, Yunyun Xu et al.

Prepared Li–CO2 catalysts with Cu–O,N active centers by solvothermal method, the battery can cycle 110 times at 200 mA g−1. The combination of TDCOF and Cu helps to accelerate electron transfer and efficient decomposition of discharge products.

Jinfang Jiang, Yiling Dong, Guangjie Han et al.

In underwater acoustic networks (UANs), communication between nodes is susceptible to long propagation delays, limited energy, and channel conflicts, and traditional multi-access control (MAC) protocols cannot easily cope with these challenges. To enhance network throughput and balance channel allocation fairness and energy efficiency, this paper proposes a multi-objective optimization MAC protocol (MOMA-MAC) based on multi-agent reinforcement learning. MOMA-MAC utilizes a delay reward mechanism combined with the Multi-agent Proximal Policy Optimization Algorithm (MAPPO) to design a dual reward mechanism, which enables agents to adaptively collaborate and compete to optimize the use of network resources. According to experimental results, MOMA-MAC performs noticeably better than traditional MAC protocols and deep reinforcement learning-based methods in terms of throughput, energy efficiency, and fairness in multi-agent scenarios, showing great potential for improving communication efficiency and energy utilization.

Sijie Liu, Nan Zhou, Chenchen Song et al.

This research introduces the Enhanced Scale-Aware efficient Transformer (ESAE-Transformer), a novel and advanced model dedicated to predicting Exhaust Gas Temperature (EGT). The ESAE-Transformer merges the Multi-Head ProbSparse Attention mechanism with the established Transformer architecture, significantly optimizing computational efficiency and effectively discerning key temporal patterns. The incorporation of the Multi-Scale Feature Aggregation Module (MSFAM) further refines 2 s input and output timeframe. A detailed investigation into the feature dimensionality was undertaken, leading to an optimized configuration of the model, thereby improving its overall performance. The efficacy of the ESAE-Transformer was rigorously evaluated through an exhaustive ablation study, focusing on the contribution of each constituent module. The findings showcase a mean absolute prediction error of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mn>3.47</mn><mo>∘</mo></msup><mi>R</mi></mrow></semantics></math></inline-formula>, demonstrating strong alignment with real-world environmental scenarios and confirming the model’s accuracy and relevance. The ESAE-Transformer not only excels in predictive accuracy but also sheds light on the underlying physical processes, thus enhancing its practical application in real-world settings. The model stands out as a robust tool for critical parameter prediction in aero-engine systems, paving the way for future advancements in engine prognostics and diagnostics.

Xuchao Ye, Qiuming Zhu, Hangang Li et al.

With the rapid development of unmanned aerial vehicles (UAVs), UAV-based communications have shown promising application prospects in beyond-fifth-generation (B5G) and sixth-generation (6G) communication. Air-to-ground (A2G) channel characteristics are significant for UAV-based wireless communications. In this paper, a multi-UAV channel measurement system is developed, which can realize cooperative, accurate, and real-time channel measurements. Measurement campaigns are performed in the campus scenario at the 3.6 GHz frequency band. Based on the measurement data, cross-correlation properties of some typical large-scale channel parameters are extracted and analyzed, including the power delay profile (PDP), path loss (PL), and shadow fading (SF). The analysis results reveal that the cross-correlation of PDP remains larger than 0.6 during the whole measurement, and the decorrelation distance is 14.765 m. The cross-correlation of SF is relatively low, and the decorrelation distance is found to be 4.628 m. These results can provide valuable references for optimizing multi-link UAV communications and node placements.

Siqi An, Guichao Cai, Xu Peng et al.

Hybrid power systems are now widely utilized in a variety of vehicle platforms due to their efficacy in reducing pollution and enhancing energy utilization efficiency. Nevertheless, the existing vehicle hybrid systems are of a considerable size and weight, rendering them unsuitable for integration into 25 kg compound-wing UAVs. This study presents a design solution for a compound-wing vertical takeoff and landing unmanned aerial vehicle (VTOL) equipped with an improved series hybrid power system. The system comprises a 48 V lithium polymer battery(Li-Po battery), a 60cc internal combustion engine (ICE), a converter, and a dedicated permanent magnet synchronous machine (PMSM) with four motors, which collectively facilitate dual-directional energy flow. The four motors serve as a load and lift assembly, providing the requisite lift during the take-off, landing, and hovering phases, and in the event of the ICE thrust insufficiency, as well as forward thrust during the level cruise phase by mounting the variable pitch propeller directly on the ICE. The entire hybrid power system of the UAV undergoes numerical modeling and experimental simulation to validate the feasibility of the complete hybrid power configuration. The validation is achieved by comparing and analyzing the results of the numerical simulations with ground tests. Moreover, the effectiveness of this hybrid power system is validated through the successful completion of flight test experiments. The hybrid power system has been demonstrated to significantly enhance the endurance of vertical flight for a compound-wing VTOL by more than 25 min, thereby establishing a solid foundation for future compound-wing VTOLs to enable multi-destination flights and multiple takeoffs and landings.

Ahmed Mahfouz, Gabriella Gaias, D. M. K. K. Venkateswara Rao et al.

In this paper, the problem of autonomous optimal absolute orbit keeping for a satellite mission in Low Earth Orbit using electric propulsion is considered. The main peculiarity of the approach is to support small satellite missions in which the platform is equipped with a single thruster nozzle that provides acceleration on a single direction at a time. This constraint implies that an attitude maneuver is necessary before or during each thrusting arc to direct the nozzle into the desired direction. In this context, an attitude guidance algorithm specific for the orbit maneuver has been developed. A Model Predictive Control scheme is proposed, where the attitude kinematics are coupled with the orbital dynamics in order to obtain the optimal guidance profiles in terms of satellite state, reference attitude, and thrust magnitude. The proposed control scheme is developed exploiting formation flying techniques where the reference orbit is that of a virtual spacecraft that the main satellite is required to rendezvous with. In addition to the controller design, the closed-loop configuration is presented supported by numerical simulations. The efficacy of the proposed autonomous orbit-keeping approach is shown in several application scenarios.

Voropay Alexey, Koriak Olexandr, Bogdan Dmytro et al.

Problem. The problems of designing, and especially improving, mechanical gears are of key importance in modern mechanical engineering and automotive transport. Gear transmissions are quite widespread relative to other mechanical transmissions because they have a number of crucial advantages. Gear transmissions are widely used in a variety of drives for vehicle components and assemblies, with modern development trends aimed at reducing their weight and size. As the size of the transmission decreases, the dimensions of other parts and assemblies also decrease, and, accordingly, their cost. Therefore, research related to the study of the interdependence of the main parameters of gears for the purpose of their further optimization does not lose its relevance. Goal. The main purpose of this work is to study the dependence of the mass and dimensions of the gears under study on their main parameters. Knowing the influence of various characteristics on the mass, it is possible to provide recommendations for the design of gears to achieve their optimal (smallest) dimensions, which leads to a number of significant advantages. Methodology. First of all, a rather detailed analysis of the scientific literature is performed in order to identify the main statements regarding the influence of certain parameters on the mass and dimensions of the designed gear. The very dependencies of the gear mass on its various characteristics are found by applying a numerical method that is entirely based on the known design dependencies for the design calculation of gears. Also, to compare the results obtained analytically, the method of calculating the mass and dimensions by creating 3D models of gears in the "Autodesk Inventor" environment is used in the work. Results. Based on the results obtained, it can be noted that, ceteris paribus, including gear load, the weight is almost independent of the module and the relative width ratio. At the same time, in some cases, a particular standard value can significantly affect the weight of the gear, i.e., by selecting specific values, it is possible to reduce the weight of the gear by about 15-25%. Originality. Useful results were obtained using a relatively affordable method. The research was conducted both analytically and with the use of modern computer-aided design systems. Practical value. The proposed recommendations for the rational choice of some characteristics of gears will reduce the weight and dimensions of the mechanical drive.

Antonio L. Diaz, Andrew E. Ortega, Henry Tingle et al.

A unique drone-based system for underwater mapping (bathymetry) was developed at the University of Florida. The system, called the “Bathy-drone”, comprises a drone that drags, via a tether, a small vessel on the water surface in a raster pattern. The vessel is equipped with a recreational commercial off-the-shelf (COTS) sonar unit that has down-scan, side-scan, and chirp capabilities and logs GPS-referenced sonar data onboard or transmitted in real time with a telemetry link. Data can then be retrieved post mission and plotted in various ways. The system provides both isobaths and contours of bottom hardness. Extensive testing of the system was conducted on a 5 acre pond located at the University of Florida Plant Science and Education Unit in Citra, FL. Prior to performing scans of the pond, ground-truth data were acquired with an RTK GNSS unit on a pole to precisely measure the location of the bottom at over 300 locations. An assessment of the accuracy and resolution of the system was performed by comparison to the ground-truth data. The pond ground truth had an average depth of 2.30 m while the Bathy-drone measured an average 21.6 cm deeper than the ground truth, repeatable to within 2.6 cm. The results justify integration of RTK and IMU corrections. During testing, it was found that there are numerous advantages of the Bathy-drone system compared to conventional methods including ease of implementation and the ability to initiate surveys from the land by flying the system to the water or placing the platform in the water. The system is also inexpensive, lightweight, and low-volume, thus making transport convenient. The Bathy-drone can collect data at speeds of 0–24 km/h (0–15 mph) and, thus, can be used in waters with swift currents. Additionally, there are no propellers or control surfaces underwater; hence, the vessel does not tend to snag on floating vegetation and can be dragged over sandbars. An area of more than 10 acres was surveyed using the Bathy-drone in one battery charge and in less than 25 min.

Li Tengda, Feng Gang, Lian Zhongmou

In order to further improve the vibration reduction optimization effect of the electromagnetic rail transmitter body tube fastening, the modal analysis method is used to simulate the selection scheme of fastening point. On the basis of simplifying the electromagnetic orbit emitter into Bernoulli-Euler beam, the vibration response analysis and modal analysis are carried out, and the whole process of emission is simulated by establishing the finite element model of the transmitter. According to the system stiffness of critical velocity, the optimal fastening position is determined and the evaluation index is put forward to evaluate the optimization effect. The simulation results show that the addition of fastening can effectively improve the stiffness of the transmitter, and the vibration absorption effect of the fastening is affected by the vibration characteristics of the fastening position, and the selection of the fastening position should avoid the resonance range of the critical velocity as far as possible, and the position is located before the arrival position of the critical speed on the premise of meeting the requirements, the addition of fastening leads to the stress concentration in the adjacent parts of the rail to improve the rail strength.

A.D. Tulegulov, D.S. Yergaliyev, B.S. Beisembayeva et al.

Background. New tasks arising almost daily lead to the emergence of new directions of machine learning. The article presents the results of the study of the main types of machine learning on the basis of the availability and complexity of data. Materials and methods. The main research method is the selection method. For each specific task, its algorithm is selected, since the speed and accuracy of the result of processing the source data depends on it. We consider methods of machine learning. In particular, an option is analyzed based on the training of an intelligent agent, which acts in the external environment and is called training with reinforcement. Reinforcement training (Eng. Reinforcement Learning) is a method of machine learning, in which the system is learning, interacting with some medium. Results. As a result of research, it is possible to note the fact that in training with reinforcement an agent interacts with the environment, taking actions and receives a reward for these actions. Conclusions. In this way, it can be argued that at the moment the classic methods of machine learning for digital technologies cover a wide range of applications from different consumers. New tasks arising almost daily lead to the emergence of new directions of machine learning.

Mahdi Ghobadi, Shafaee Maziar, Mahdi Jafari Nadoushan

An optimal thruster configuration for attitude control subsystem of a spacecraft is presented in this paper. The optimal configuration is designed according to minimum number of required thrusters for satisfying desired reliability with specific redundancy level. The genetic algorithm is employed for optimization process and feasibility of the results is evaluated using algebraic and geometry methods. The main feature of the proposed configuration among feasible configuration with minimum number of required thrusters, which has held to optimal configuration, is that this configuration has maximum reliability and minimum fuel consumption. In addition to feasibility, attitude control performance of some configurations is also examined through the simulation. The results of simulation confirm that the proposed configuration has desirable performance. It is noteworthy to mention that the configuration with maximum number of required thrusters, which is a conventional configuration such that each thruster belongs to only one control channel, has less fuel consumption than optimal configuration. However, the total mass of optimal configuration is less than that of conventional configuration due to a smaller number of thrusters.

Mohammad Razmjooei, Zaheer Sabohi

This paper reports a review and comparison of the methods used for calculating convective heat transfer coefficient in combustion chambers and in diverging-converging nozzles. Therefore, a history of applying different methods for calculating the convective heat transfer coefficient is explained first. Then, the nozzle flow is numerically solved, using the explicit McCormack method. In a Bates nozzle, The methods of Bartz, Stanton, Preiskorn, and Adami were selected among the proposed methods and were compared with CFD. Convective heat transfer coefficient of a solid fuel engine was calculated by taking into account the flow parameters in the engine chamber. Consequently, it was found that as wet move to the nozzle, heat transfer coefficient increases with velocity of the flow. This results revealed that in analytical methods, the maximum convective heat transfer coefficient occurs in the nozzle throat, while CFD results show that the maximum occurs upstream of the nozzle throat. These methods require less computational time than CFD, however CFD has to be considered more accurately. As a result, during a preliminary design procedure, the much faster and slightly less precise method can be used, in particular at the throat where the relative difference between the methods is quite low. Finally, it was shown that the innovative approach of combining Adami and Bartz methods has the lowest possible error, compared to the CFD.

İlkay Gümüşboğa, Altuğ İftar

In this work, a detailed nonlinear model for the full dynamics of the F-16 aircraft is first developed and coded in MATLAB. This model includes the gravity model, variable atmospheric parameters, tabular aerodynamic functions, propulsion model, nonlinear control surface actuation models, and six degrees of freedom equations of motion. A numerical tool for computing all possible trim values, using the aforementioned model, is then developed. This tool can calculate the trim values at different operating points. In the developed algorithms, particle swarm optimization (PSO) method, which is a meta-heuristic method with a high convergence rate over a continuous search space, is used. Simulations around the calculated trim values are then made using the developed model. Simulation results confirm that the PSO based trim algorithm can find all the trim values with a high accuracy.

V. V. Ryzhkov, I. I. Morozov

The article presents the results of comparison of computation data on the energy parameters of the working process of engines and the thermal condition of the structure obtained for low-thrust rocket engines fueled by gaseous oxygen-hydrogen, using various schemes of mixture formation. The analysis of the efficiency of the working process is carried out on the basis of the patterns of distribution of combustion products temperature in the cross sections of combustion chambers, temperature diagrams, their values in the area of the engine chamber wall and the specific thrust impulse. It is shown that the chosen tools fully characterize the efficiency of the working process implemented in various schemes of mixing in engines and make it possible to assess the quality of a particular scheme. It was found that for most of the parameters used and additional criteria for evaluating the efficiency of the mixture formation scheme for low-thrust rocket engines, the scheme implementing a rotational coaxial multistage flow of gaseous fuel components in the chamber is preferable.

Meng-Sang Chew, Onur Denizhan

Equipment such as a rod between vehicle body and hood or a lift strut are used to keep automobile hood in open positions during the regular maintenances or repairs. Moreover, some effort is required to open or close automobile hood because of its weight. To keep it in various opened positions and to exert the least force to open or close it, a mechanism is used in conjunction with extension, compression or torsion springs in two different configurations. Each optimization has been carried out for all these different springs, each in two configurations and results are compared. Sensitivity analysis for the design variables are examined to determine how these variables are influential on the designed mechanism. Optimization results of extension and compression springs are observed to be similar in both configurations of the designed mechanism. On the other hand, results for the torsion spring in two configurations are exactly the same for the mechanism. Sensitivity analysis shows that the designed mechanism is not sensitive on the design variables that are on the bound in both of these two configurations.

CHEN Yanxia, YANG Yanqing

The microstructural and crystallographic features of the surface deformation layer in Al-Zn-Mg-Cu alloy induced by milling were investigated by means of transmission electron microscopy (TEM) and precession electron diffraction (PED) assisted nanoscale orientation mapping. The result shows that the surface deformation layer is composed by the top surface of equiaxed nanograins/ultrafine grains and the subsurface of lamellar nanograins/ultrafine grains surrounded by coarse grain boundary precipitates (GBPs). The recrystallized nanograins/ultrafine grains in the deformation layer show direct evidence that dynamic recrystallization plays an important role in grain refining process. The GBPs and grain interior precipitates (GIPs) show a great difference in size and density with the matrix due to the thermally and mechanically induced precipitate redistribution. The crystallographic texture of the surface deformation layer is proved to be a mixture of approximate copper{112}<111>, rotated cube{001}<110> and F {111}<112>. The severe shear deformation of the surface induced by milling is responsible for the texture evolution.