Hasil untuk "Motor vehicles. Aeronautics. Astronautics"

Yang Du, Jun Liu

Experimental Research: The current development of high-enthalpy wind tunnels is reviewed, highlighting their potential to simulate real flight conditions. However, improvements in facility speed and magnetic field strength are required. Advanced simulation technologies and superconducting magnet optimization are essential for effective flow control, alongside addressing the Hall effect in MHD systems.

Emma Cassidy, Paul R. Mokotoff, Yilin Deng et al.

This study evaluates the feasibility and benefits of introducing battery-powered hybrid electric aircraft (HEA) into regional airline operations. Using 2019 U.S. domestic flight data, the ERJ175LR is selected as a representative aircraft, and several HEA variants are designed to match its mission profile under different battery technologies and power management strategies. These configurations are then tested across over 800 actual daily flight sequences flown by a regional airline. The results show that well-designed HEA can achieve 3–7% fuel savings compared to conventional aircraft, with several variants able to complete all scheduled missions without disrupting turnaround times. These findings suggest that HEA can be integrated into today’s airline operations, particularly for short-haul routes, without the need for major infrastructure or scheduling changes, and highlight opportunities for future co-optimization of aircraft design and operations.

Wen Zou, Zhanxin Cui, Genghui Li et al.

In the field of aerospace, solving the boundary problem associated with the parachute-capsule system remains a big challenge. The conventional Monte Carlo method proves inadequate for acquiring comprehensive boundary information. To address this issue, this paper introduces a novel tube prediction scheme by leveraging the natural geometric characteristics of the reachable tube and employing a multiobjective optimization strategy. Initially, a multibody dynamic model with nine degrees of freedom was established and verified by the airdrop test data to ensure the accuracy and reliability of the model. Subsequently, the Sobol sensitivity analysis method was employed to assess uncertain factors that affect the deceleration phase of the reentry capsule. These factors are then utilized to determine the optimization parameters for the multiobjective optimization model. Ultimately, the multiobjective evolutionary algorithm based on decomposition was employed to solve the multiobjective optimization model, and the geometric boundary of the tube corresponds to the Pareto front of the multiobjective optimization. The proposed methodology was validated through a simulation experiment utilizing the Chang’e-5 reentry capsule as an engineering case. The experimental results unequivocally demonstrate the superior accuracy of our approach in predicting the boundary of the reachable tube compared to the Monte Carlo method. This research serves as a valuable reference for calculating reachable tubes in practical engineering scenarios and can be effectively applied to spacecraft search and rescue operations during the reentry phase.

Duo Xu, Honghao Yue, Yong Zhao et al.

For future large-scale CubeSat applications in orbit, the deployer must accommodate a greater number of CubeSats and facilitate cluster releases. This paper introduces an improved A* algorithm tailored for CubeSat in-orbit transfer path planning. Unlike the traditional A* algorithm, this enhanced version incorporates a path coordination strategy to manage congestion caused by the simultaneous transfer of many CubeSats, ensuring they reach their designated release positions smoothly and thus significantly boosting the efficiency of CubeSat transfers. Additionally, the algorithm develops a cost model for attitude disturbances on the electromagnetic conveying platform and crafts an improved cost function. It strategically balances the reduction in attitude disturbances caused by CubeSat transfers with the efficiency of these transfers. The primary goal is to minimize platform disturbances while optimizing the number of steps CubeSats need to reach their intended positions. The effectiveness of this algorithm is demonstrated through detailed case studies, which confirm that during the CubeSat transfer process, the platform’s attitude remains stable, and the transfer efficiency is well-managed, achieving efficient path planning for the in-orbit transfer of numerous CubeSats.

Yu Tian, Luofeng Wang, Zhongliang Zhou et al.

In order to reveal the mechanism of Category II rotor-body-slung-load coupled oscillation (RBSLCO) with the frequency range of 2.5~8 Hz, a novel nonlinear rigid-elastic coupled model is presented for the helicopter and slung load system (HSLS) with explicit formulation. The slung load system model is coupled with the current rigid-elastic coupled helicopter model, considering fuselage hook point rigid-elastic coupled movements, cable stretching, and hook point force from the slung load system. The results show that carrying the heaviest load is the vital state for Category II RBSLCO. As slung load mass ratio increases, rotor-fuselage coupling becomes stronger and the oscillation frequency shifts slightly, causing a maximum of 15% reduction in stability margin. In addition, even when the load is lightweight, another form of Category II RBSLCO may appear involving fuselage bending and cable stretching. This Category II RBSLCO behaves like the vertical bouncing but is divided into a high-frequency anti-phase oscillation and a relatively low-frequency in-phase oscillation.

Tiwei Zeng, Jihua Fang, Chenghai Yin et al.

Rubber tree is one of the essential tropical economic crops, and rubber tree powdery mildew (PM) is the most damaging disease to the growth of rubber trees. Accurate and timely detection of PM is the key to preventing the large-scale spread of PM. Recently, unmanned aerial vehicle (UAV) remote sensing technology has been widely used in the field of agroforestry. The objective of this study was to establish a method for identifying rubber trees infected or uninfected by PM using UAV-based multispectral images. We resampled the original multispectral image with 3.4 cm spatial resolution to multispectral images with different spatial resolutions (7 cm, 14 cm, and 30 cm) using the nearest neighbor method, extracted 22 vegetation index features and 40 texture features to construct the initial feature space, and then used the SPA, ReliefF, and Boruta–SHAP algorithms to optimize the feature space. Finally, a rubber tree PM monitoring model was constructed based on the optimized features as input combined with KNN, RF, and SVM algorithms. The results show that the simulation of images with different spatial resolutions indicates that, with resolutions higher than 7 cm, a promising classification result (>90%) is achieved in all feature sets and three optimized feature subsets, in which the 3.4 cm resolution is the highest and better than 7 cm, 14 cm, and 30 cm. Meanwhile, the best classification accuracy was achieved by combining the Boruta–SHAP optimized feature subset and SVM model, which were 98.16%, 96.32%, 95.71%, and 88.34% at 3.4 cm, 7 cm, 14 cm, and 30 cm resolutions, respectively. Compared with SPA–SVM and ReliefF–SVM, the classification accuracy was improved by 6.14%, 5.52%, 12.89%, and 9.2% and 1.84%, 0.61%, 1.23%, and 6.13%, respectively. This study’s results will guide rubber tree plantation management and PM monitoring.

Wentao Wang, Chen Ye, Jun Tian

The application of 3D UAV path planning algorithms in smart cities and smart buildings can improve logistics efficiency, enhance emergency response capabilities as well as provide services such as indoor navigation, thus bringing more convenience and safety to people’s lives and work. The main idea of the 3D UAV path planning problem is how to plan to get an optimal flight path while ensuring that the UAV does not collide with obstacles during flight. This paper transforms the 3D UAV path planning problem into a multi-constrained optimization problem by formulating the path length cost function, the safety cost function, the flight altitude cost function and the smoothness cost function. This paper encodes each feasible flight path as a set of vectors consisting of magnitude, elevation and azimuth angles and searches for the optimal flight path in the configuration space by means of a metaheuristic algorithm. Subsequently, this paper proposes an improved tuna swarm optimization algorithm based on a sigmoid nonlinear weighting strategy, multi-subgroup Gaussian mutation operator and elite individual genetic strategy, called SGGTSO. Finally, the SGGTSO algorithm is compared with some other classical and novel metaheuristics in a 3D UAV path planning problem with nine different terrain scenarios and in the CEC2017 test function set. The comparison results show that the flight path planned by the SGGTSO algorithm significantly outperforms other comparison algorithms in nine different terrain scenarios, and the optimization performance of SGGTSO outperforms other comparison algorithms in 24 CEC2017 test functions.

Guo Li, Junbo Liu, Huimin Zhou et al.

Numerical integration methods have the characteristics of high efficiency and precision, making them attractive for aero-engine probabilistic risk assessment and design optimization of an inspection plan. One factor that makes the numerical integration method a suitable approach to in-service inspection uncertainties is the explicit derivation of the integration formula and integration domains. This explicit derivation ensures accurate characterization of a multivariable system’s failure risk evolution mechanism. This study develops an efficient numerical integration algorithm for probabilistic risk assessment considering in-service inspection uncertainties. The principle of probability conservation is applied to the transformation of the integration domain from the current flight cycle to the initial (<i>N</i> = 0) computational space. Consequently, the integration formula of failure probability is deduced, and a detailed mathematical demonstration of the proposed method is provided. An actual compressor disk is evaluated using the efficient numerical integration algorithm and the Monte Carlo simulation to validate the accuracy and efficiency of the proposed method. Results show that the time cost of the proposed algorithm is dozens of times lower than that of the Monte Carlo simulation, with a maximum relative error of 5%. Thus, the efficient numerical integration algorithm can be applied to failure analysis in the airworthiness design of commercial aero-engine components.

Üsame Demir, Ozan Çetinkaya, Anil Can Türkmen et al.

Intake port geometry is the most significant parameter for air supply of engines into combustion space. Especially because only air is supplied into combustion spaces of diesel engines and the fuel is sprayed over the air, intake port geometry should form a specific horizontal turbulence ratio in formation of fuel-air mixture. In this study, the impact of cylinder heads of intake port of a single cylinder compression ignition engine produced with 3 different geometries on performance and emissions of the engine was analysed experimentally. Additionally, the impact of intake port geometry produced with old and new moulds on 3 different geometries was researched. As a result of the study; power, torque, specific fuel consumption, exhaust gas temperatures, intake air flow and soot emission were measured. It was found out that the different intake port designs had impact on performance parameters, specific fuel consumption and soot emission following the study. Moreover, it was shown that the change of intake port didn’t have any impact on the flow of the air intake in low speed. It was observed that the cylinder heads produced with old and new mould cores had a significant impact. It is predicted that the main reason for the poor performance of the port geometry, which is called Y-type and creates a wider auger around the intake valve, may be due to the low turbulence intensity it creates in the cylinder. X and Z type ports gave better results by about 15% in power and torque values. Z type intake port gave the best performance in terms of exhaust gas temperature and soot emission.

Mohammad Alimohammadi, Ali Davar, Mohsen Heydari Beni et al.

Microgravity and cosmic radiation are the space environmental stresses which can cause DNA damage in living organisms. Radiations injurie the cell DNA directly through the interaction of charged particles with DNA molecules or indirectly by the production of free radicals. In addition, radiation can alter cell wall composition, activate free radical scavenging enzymes, and accumulate antioxidant compounds. Although plants have evolved some mechanisms to deal with the damages, space conditions, especially microgravity can play a role in repairing DNA damage. More DNA damages can induce double strands breaks of DNA, chromosome abnormality, micro-nuclei formation, and increase the risk of cell death. In this study, effect of space environmental stresses on DNA damage and response mechanisms will be investigated in space flight or simulated conditions.

Kalani Gunaratne, Amila Thibbotuwawa, Alex Elkjær Vasegaard et al.

Low-income countries are persistently suffering from last-mile logistics issues in healthcare supply chains. Therefore, it is high time to explore technological applications to overcome such inadequacies. The faster speed, low maintenance cost, and absence of road dependency in unmanned aerial vehicles (UAV) have popularized them as an alternative to road delivery. Hence, it is suggested as a solution to overcome the persisting distribution inefficiencies in healthcare logistics of low-income countries. According to the case study analysis conducted on the Sri Lankan vaccine cold chain, incorporating UAVs increases truck-space utilization and reduces the time consumed, cost incurred, and carbon dioxide emission in a delivery round. Moreover, the most suitable way to cover the initial setup cost of an unmanned aerial system (UAS) is by receiving aid from international donors. The capital cost also can be covered by government investments or via service outsourcing only if the number of flights per year is increased. Moreover, a homogenous (i.e., only UAV) solution was revealed to be more beneficial than a heterogeneous (i.e., truck and UAV) solution. However, due to the lack of technology literacy and willingness to change in low-income countries, it is recommended to initially execute a heterogeneous solution and expand to a homogeneous plan in the future years. However, it was evident that for a mixed-fleet solution to be advantageous, drone characteristics play a vital role. Hence, a UAV with specifications ideal for the use case must be utilized to garner the maximum benefits. Nevertheless, it was apparent that with the right implementation plan, UAVs possess the potential to overcome the shortcomings in the healthcare logistics of low-income countries.

Jian Liu, Chunfeng Li

Component mismatch often happens in the module-series photovoltaic system(including centralized, string, multi-strings PV system) due to partial shadowing, which causes a large loss of power generation. Photovoltaic equalizer can process the differential power under the condition of mismatching through parallel power electronic converter without changing the existing photovoltaic system architecture, so that all the modules can work near their maximum power points, which can greatly improve the power generation of the system under the condition of mismatching. This paper proposes a photovoltaic equalizer based on single-input multi-output push-pull converter. The topology has the advantages of simple structure and less switching devices. Firstly, the paper introduces the partial shadowing problem of photovoltaic modules and the principle of photovoltaic equalizer. Then, the topological structure and working principle of the proposed photovoltaic equalizer system are analyzed in detail. Finally, the simulation and verification of the designed photovoltaic equalizer are carried out. The simulated results show that the proposed equalizer can greatly improve the generation capacity of photovoltaic system under mismatching conditions, and the maximum increment can be up to 41%.

Drones Editorial Office

The editorial team greatly appreciates the reviewers who have dedicated their considerable time and expertise to the journal&#8217;s rigorous editorial process over the past 12 months, regardless of whether the papers are finally published or not [...]

Hnatov Andrii, Arhun Shchasiana, Hnatova Hanna et al.

Problem. The danger posed by high-speed vehicles passing through crowded areas is extremely high. An analysis of the cause of accidents involving victims in Ukraine showed that speeding was the main cause for that in the city. Therefore, one of the main means of reducing the causes of road traffic accidents involving pedestrians is artificial road irregularities, also called «speed bumps». Goal. Development of a device for generating electricity and forcing reduction of the speed of vehicles at pedestrian crossings and other sections of the road where there is a need to reduce the speed of vehicles. Meth-odology. The analytical methods of research on the development and application of methods and devices for transforming the energy of the sun into electricity were used. Methods of experimental researches and mathematical methods of processing and modulation of the obtained results are used. Results. The result is the analysis of the technical solutions for the devices of forced reduction of the car speed. The design of the device of forced reduction of the car speed with the function of electricity generation is developed, as well as its schematic drawings and the schematic diagram, which are shown. The principle of opera-tion of the developed device of forced reduction of car speed is revealed. One of the variants of the pe-destrian crossing with additional lighting and laser signaling system is offered, which is equipped with devices of forced reduction of car speed with the function of electricity generation. Originality. The amount of electricity that the proposed device is able to generate is modulated (depending on the traffic intensity) from 60 kW to 400 kW. Practical value. The implementation of the proposed development into road construction will lead to the implementation of energy-efficient technologies in this field and will significantly improve road safety. Pedestrian crossings equipped with additional lighting and a laser signaling system to alert road users when using these devices will receive power from a decentralized, renewable power source.

Bharat Ankur DOGRA, Mehakveer SINGH, Tejinder Kumar JINDAL et al.

Pulse Detonation Engine (PDE), is an emerging and promising propulsive technology all over the world in the past few decades. A pulse detonation engine (PDE) is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. Theoretically, a PDE can be operate from subsonic to hypersonic flight speeds. Pulsed detonation engines offer many advantages over conventional air-breathing engines and are regarded as potential replacements for air-breathing and rocket propulsion systems, for platforms ranging from subsonic unmanned vehicles, long-range transportation, high-speed vehicles, space launchers to space vehicles. This article highlights the operating cycle of PDE, starting with the fuel-oxidizer mixture, combustion and Deflagration to detonation transition (DDT) followed by purging. PDE combustion process, a unique process, leads to consistent and repeatable detonation waves. This pulsed detonation combustion process causes rapid burning of the fuel-oxidizer mixture, which cannot be seen in any other combustion process as it is a thousand times faster than any other mode of combustion. PDE not only holds the capability of running effectively up to Mach 5 but it also changes the technicalities in space propulsion. The present paper is the extension of the previous study which is also a well characterized status report of PDE in different areas. The present study deals with the categorization of the design approach, computations & simulations, flow visualization, DDT & Thrust enhancement, PDRE’s, experimental detonation engines with some of the experience and research undertaken in Punjab Engineering College under the complete supervision and guidance of Prof. Tejinder Kumar Jindal followed by applications of PDE technology.

Zhang Fei, Wang Yun, Sun Yifang et al.

Vertical takeoff and landing(VTOL) fixed-wing UAV has the advantages of fast speed, long range, vertical takeoff and landing and hovering operation of fixed-wing UAV. It is of great significance to study the influence of the vertical tail of its wing tip on the aerodynamic characteristics of the whole UAV. The vertical take-off and landing fixed-wing UAV is designed with the drooping tail of the wing tip to be used as a vertical tail with both wingtips and landing gear. Four wingtip designs of the drooping tail, upper vertical tail, wing tip end plate and conventional layout are compared the aerodynamic characteristics of the four designs are simulated and analyzed by using LBM-LES algorithm and the wall self-adaptive local vortex viscous large eddy simulation turbulence model. The analysis results show that the drooping tail of the wing tip is more efficient than the other three designs in the leveling flight state; and its stability against the crosswind is better in the vertical takeoff and landing or hovering state.

Andrew Viquerat

Aleksander Muc

Free vibration (or eigenvalue analysis) is a prerequisite for aeroelastic analysis. For divergence analysis, slope influence coefficients (rotation at point i due to unit load at point j) are calculated using free vibration mode shapes and corresponding frequencies. The lowest eigenvalue is of interest and gives the divergence speed. The present paper considers the maximization problem of eigenfrequencies for composite panels. The influence of boundary conditions and constant or variable stiffnesses on optimization results are investigated herein. A new convenient set of design variables is employed in the analysis. The computations are carried out with the use of the Rayleigh&ndash;Ritz method and Finite Element analysis (2D quadrilateral and 3D solid elements).