Hasil untuk "Motor vehicles. Aeronautics. Astronautics"

YUAN Xujiong, HAO Yaming, HU Yue et al.

High-temperature microwave-absorbing materials play a crucial role in enhancing the stealth capabilities of hot-end components in advanced warplanes. Among them，Al2O3 and Ti3SiC2 have a wide range of applications in this field. However，the two powders have poor fluidity after physical mixing，which makes them difficult to use directly for plasma spraying，so secondary granulation is required. In this research，agglomerated powders composed of Al2O3 and Ti3SiC2 are successfully prepared using centrifugal spray drying. The study indicates the influence of various factors，including slurry solid content，PVA solution content，spray disk rotational speed，inlet air temperature，and outlet air temperature，on the morphology，surface roughness，and particle size distribution of the agglomerated powders.The results show that optimizing the content of solid and PVA in the slurry is beneficial to improve the sphericity and surface roughness of the powder，controlling the rotational speed of the spray disk can effectively control the particle size distribution of the powder，and a reasonable inlet/outlet temperature will help to further improvement of the sphericity of the powder. Optimal conditions for producing high-quality agglomerated powders are：60% solid content，3% PVA solution content，a spray disk rotational speed of 40 r·min−1，an inlet air temperature of 250 ℃，and an outlet air temperature of 130 ℃. Under these conditions，the agglomerated powders exhibit high sphericity，low surface roughness，a bulk density of 1.92 g·cm−3，a fluidity of 37.1 s/50 g，and a tightly concentrated particle size distribution（D10 = 30.1 μm，D50 = 56.7 μm，and D90 = 90.1 μm）. These powders，obtained through this method，can be directly utilized in plasma spraying and are suitable for large-scale production，thereby holding significant promise for the research and development of high-temperature wave-absorbing materials based on Al2O3 and Ti3SiC2.

Suping Zhao, Chenghang Wang, Alejandro Gutierrez–Giles et al.

Unmanned aerial manipulators (UAMs), composed of unmanned aerial vehicles (UAVs) and manipulators, have great application potential in aerial manipulation like precision inspection, disaster rescue, etc. However, strong dynamic coupling exists between UAVs and manipulators. In addition, UAMs meet external disturbances such as gusts of wind during movements. Also, the control performance metrics, such as tracking accuracy and control stability, are seriously affected. Therefore, a cooperative control method is developed for a UAM system with a UAV and a 2-degree-of-freedom manipulator. First, the Euler–Lagrange formulation is employed to study the UAM dynamics like inertial forces and coupling effects. Then, an integral sliding mode control (ISMC) method with an integral term is developed to enhance robustness and eliminate steady-state errors. Finally, the proposed ISMC method is validated through numerical simulations in Matlab R2024a, introducing comparative analyses with the Proportional–Integral–Derivative (PID) and SMC controllers. The simulation results and the comparative analyses validate the effectiveness of ISMC, showing its superiority over the PID and SMC controllers in handling dynamic coupling and external disturbances, where the overshoot of ISMC is reduced by an average of more than 90%. The ISMC method provides a high-performance control strategy to promote the practical application of UAMs in various aerial manipulation tasks and lays the foundation for further optimizing control methods for more complex UAM systems.

Joachim Wallisch, Markus Lindner, Øyvind Wiig Petersen et al.

Electrothermal de-icing systems are a popular approach to protect unmanned aerial vehicles (UAVs) from the performance degradation caused by in-cloud icing. However, their power and energy requirements must be minimized to make these systems viable for small and medium-sized fixed-wing UAVs. Thermal de-icing systems allow intercycle ice accretions and can result in runback icing. Intercycle and runback ice increase the aircraft’s drag, requiring more engine thrust and energy. This study investigates the aerodynamic influence of intercycle and runback ice on a typical UAV wing. Lift and drag coefficients from a wind tunnel campaign and Ansys FENSAP-ICE simulations are compared. Intercycle ice shapes result in a drag increase of approx. 50% for a realistic cruise angle of attack. While dispersed runback ice increases the drag by 30% compared to the clean wing, a spanwise ice ridge can increase the drag by more than 170%. The results highlight that runback ice can significantly influence the drag coefficient. Therefore, it is important to design the de-icing system and its operation sequence to minimize runback ice. Understanding the need to minimize runback ice helps in designing viable de-icing systems for UAVs.

CHEN Tianxie, SHEN Yan, KANG Weifeng et al.

Ceramic fiber sponge with low density，high specific surface area，high porosity，good thermal stability and good thermal insulation performance is expected to become one of the most promising commercial ceramic materials in the fields of heat insulation，flame retardant，water-oil absorption and energy conversion. This paper summarizes the direct assembly methods such as three-dimensional electrospinning，solution blowing spinning and centrifugal spinning，reviews the research progress in the production of ceramic fiber sponge by direct spinning method，analyses the problems of low production efficiency of ceramic fiber sponge，and proposes the future development directions of ceramic fiber sponge：（1）improve the production efficiency，reduce the production cost，and mass produce ceramic fibre sponge with controllable shape；（2）improve the high-temperature thermal insulation performance and promote the application of ceramic fibre sponge in the field of heat insulation；（3）improve the structural stability and produce ceramic fibre sponge with high elasticity，flexibility，and fatigue resistance；（4）research and develop ceramic fibre sponge materials with special functions such as light and electromagnetism，and expand the application range of ceramic fibre sponge.

Xianghua Zhou, Cong Niu, Shan Jia et al.

For the needs of manned landing, station construction, and material transfer in future lunar exploration missions, the paper proposes a landing–moving integrated gear (LMIG) for mobile lunar lander (MLL), establishes and optimizes the models of cushioning energy-absorbing and movement planning, respectively, and conducts the prototype tests. First, the design requirements of LMIG are given, and the system composition of LMIG and the configuration design of each subsystem are introduced. Second, the effective energy-absorbing model of the aluminum honeycomb is established and experimentally verified, a three-stage aluminum honeycomb buffer is designed and experimentally verified, and the buffer mechanism of LMIG is verified by simulations under various landing conditions. Furthermore, the kinematic and dynamic models of LMIG are established, the moving gait is designed by the center of gravity trajectory planning method, and the driving trajectory during the stepping process is optimized with the goal of minimal jerk of motion. Finally, a cushioning test prototype and a walking test scaled prototype of LMIG are developed, and single leg drop test and ground walking test are carried out. The results show that the established model of LMIG is reasonable, the designed buffer and gait of LMIG are effective, the developed prototypes of LMIG have good cushioning and movement performance, the LMIG’s maximum value of overload acceleration is 6.5g, and the moving speed is 108 m/h, which meets the design requirements.

Wenhong Zhou, Jie Li, Qingjie Zhang

Communication is the cornerstone of UAV swarms to transmit information and achieve cooperation. However, artificially designed communication protocols usually rely on prior expert knowledge and lack flexibility and adaptability, which may limit the communication ability between UAVs and is not conducive to swarm cooperation. This paper adopts a new data-driven approach to study how reinforcement learning can be utilized to jointly learn the cooperative communication and action policies for UAV swarms. Firstly, the communication policy of a UAV is defined, so that the UAV can autonomously decide the content of the message sent out according to its real-time status. Secondly, neural networks are designed to approximate the communication and action policies of the UAV, and their policy gradient optimization procedures are deduced, respectively. Then, a reinforcement learning algorithm is proposed to jointly learn the communication and action policies of UAV swarms. Numerical simulation results verify that the policies learned by the proposed algorithm are superior to the existing benchmark algorithms in terms of multi-target tracking performance, scalability in different scenarios, and robustness under communication failures.

Qiu Tianhui, Xia Xiaojuan, Liu Qi, Guan Yu

To meet the needs of the third generation infrared detector, a design of 1 280×1 024 pixel infrared readout circuit with large array and low power consumption is proposed. Based on the analysis of each module, low-power readout and working sequence of super array pixel unit are mainly designed, which improves the driving ability of the output buffer to the external system, and the integration while reading and multi-channel output functions are realized. Under the working conditions of temperature of 80 K and clock frequency of 5 MHz, 4-way and 8-way readout and linearity simulations of pixel array window are performed. The output frame rate could reach 60 Hz, the output voltage swing is 1.6~4.8 V, the maximum power consumption is less than 450 mW, and the linearity is 97.76%.

Jian-Liang Gong

The coupling thermal and mechanical effect on submerged nozzles is important in the design of modern rockets upon thermal loading and aerodynamic pressure. In this paper, a simulation with the subroutine of nonuniform pressure and nonuniform heat transfer coefficient was conducted to study the thermo-structural response of a submerged nozzle at the pressure 6 MPa and stagnation temperature 3200 K. Both the aerodynamic parameters and heat coefficients were obtained through analyzing the flow field. It was found that the thermal loading had an important influence on the stress of throat insert for the solid rocket motor (SRM). The hoop stress increases at first and then decreases with the increase of time for the throat insert. The ground hot firing test of SRM with a submerged nozzle was carried out. The experimental results showed that the structural integrity of the submerged nozzle is very normal during SRM operation. The present method is reasonable, which can be applied to study the thermo-structural response of submerged nozzle for SRM.

The initial satellite telemetry data acquired by ground stations usually contain noise and outlier interference. In order to ensure the accurate analysis of satellite status, the telemetry data need to be filtered. In this paper, a sliding window optimal tracking differentiator filtering (SWOTDF) method for satellite telemetry data is proposed. Aiming at the problem of parameter selection during the filtering of the optimal tracking differentiator, the amplitude-frequency characteristics of the maximum tracking differentiator are analyzed by sine sweep frequency method, and the mapping relationship between tracking factors and filtering effects is established. On this basis, the telemetry data are divided by sliding windows, and the relationship between local stability of data in each window and tracking factors is further analyzed. The calculation method of local data tracking factor is given to realize dynamic optimal tracking differentiator filtering of telemetry data in each window. Experimental results show that the SWOTDF method can effectively avoid the limitations of traditional digital filters in processing nonlinear telemetry data, and can effectively filter out noise and outliers in satellite telemetry data.

Ван Зионг Нгуен, Александр Витальевич Белогуб

The paper deals with the study of the influence of the working process parameters of the two-stroke opposed piston engine like D100 (20.7/2×25.4), especially the heat exchange between the working substance and the wall of the combustion chamber (CC) – cylinder and pistons on temperature and stress-strain state of the piston. To make an estimation of the effect of a working process on the boundary condition we considered the internal heat balance and specific features of gas dynamic loading of main parts of the cylinder-piston group. To calculate the temperature fields, the actual boundary conditions of non-stationary thermal loading were replaced with the equivalent steady-state ones, obtained from the condition that the amount of heat perceived by the piston surface in real and conditionally equivalent processes are equal. Equivalent parameters of heat transfer are calculated by the condition of conservation of the amount of heat passing through the walls of the CS. It was performed the validation of the calculation of equivalent heat exchange parameters. It is shown that in case of an error in specifying the initial conditions, for example, temperature per 100K, the temperature of the piston CC surface may change by 5K in the first 5 operating cycles. It is shown that the developed model of the workflow can be adjusted according to the available experimental data and used to model the boundary conditions. The authors made corrections to the dependence obtained by prof. Rosenblit, to determine the current heat transfer coefficient from the working fluid to the walls of the CC by the total heat removal for the cycle, equal to 20%. It was obtained the average coefficient of heat transfers from the working fluid to the piston and the temperature of the cycle for the nominal mode, which are 3500 W/(m2•K) and 835 K respectively. It was carried out the simulation of the thermal properties of the gap between the piston ring and the groove filled with combustion products. It is shown that the conditions of heat transfer through annular grooves and rings require clarification in modeling, which is associated with the conditions of heat transfer in the gaps, and the gap can be replaced by a gasket with appropriate thermal properties.

A. I. Stepnova, S. M. Stepanov, V. V. Borsoeva et al.

Training of cadets-air traffic controllers and cadets-pilots is an integral part of the training, which allows you to form the skills of quick and correct decision-making in different types of situations. For the air traffic controller, these are exercises to solve conflict situations with aircraft in the area of their responsibility, solving problems in normal flight conditions, in unfavorable atmospheric conditions and in the non-routine situations in flight. For the pilots, solutions to the problems are reduced to the rapid decisionmaking on aircraft control in normal flight conditions, adverse atmospheric conditions and non-routine situations in flight. As you know, the work of air traffic controllers is associated with the work of pilots, but training in educational institutions takes place separately, resulting in gaps in knowledge of the specifics of the adjacent specialty, and, eventually, leads to errors. Optimization of the educational process is currently an urgent task. The program of joint training can act as an optimization tool. The program enables you to collaboratively practice the skills of fast decision-making, clearly to learn the specifics of the related specialties that will allow you to create a complete picture of the air situation. The program of joint training implies the joint operational logic simulator that combines two simulators. For the air traffic controller, this is a separate airspace area in the form of a sector, for the pilot it is the cockpit. Thus, the solution to the problems occurs sequentially from the air traffic controller to the pilot and vice versa, and the controller has the ability to observe the algorithm of the pilot's actions, and the pilot is able to monitor the algorithm of the controller's actions.

M. V. Siluyanova, A. O. Fertikov

Modifying the working surface of a product by applying protective and functional coatings makes possible considerable changes in the mechanical, optical, electrical, magnetic, thermal and chemical properties of the original structural material, its real surface, producing articles with protective, for example, anti-corrosion, wear-resistant and other properties. We investigated the possibility of improving the friction units of aircraft power plants by applying nanostructured ceramic composite spray coatings. A heavily loaded bearing forming a part of the gearbox of a turbojet engine is used as a prototype of the friction unit. The advantages and drawbacks of improved friction units as compared to production models and their prototypes made according to an improved technology are assessed. The results obtained during the experimental work are presented. A positive conclusion is made about the use of nanostructured composite materials in the development of friction units; the most favorable method of coating is determined.

Le Anh Son, Tatsuya Suzuki, Hirofumi Aoki

We have developed a method to estimate driver distraction by mean of involuntary eye movement of the vestibulo-ocular reflex (VOR) and optokinetic response (OKR) by using a driving simulator. This paper presents a practical application of the method to the real vehicle situation. The main concern was whether we can measure the eye movement of VOR and OKR caused by the road surface vibration in the situation. The experiments were conducted with participants sitting on the passenger seat for safety reasons. The results have shown that our method can be applied for evaluating cognitive distraction not only in a driving simulator but also in actual vehicles.

Priori geomagnetic information is important to the geomagnetic navigation. However in practice, the precision of the geomagnetic information is a greatly constraint to the development of the geomagnetic navigation. In order to solve this problem, this paper present a geomagnetic gradient bionic navigation method based on parallel approach without any priori information. Inspired by the evidence that many creatures can navigate using the Earth magnetic field, the navigation process can be considered as a convergence of multi-objective problem, and develop the bionics navigation model. By introducing the parallel approach method to the navigation process, the heading angle can be estimated with the information of magnetic field gradient. The simulation results show the proposed method is able to navigation effectively without magnetic priori information, just rely on the actual geomagnetic measurement, which has implies potential application in the future.

Pogrebnyak A., Yevtushenko A., Kravets A.

The proposed stand is designed to test sealing and bearing units of various types, because these units, regardless of their type, require almost the same auxiliary stand systems, as well as practically the same measurement system. The stand allows carrying out in-situ tests of contact, non-contact and combined sealing, supporting and thrust hydrodynamic and hydrostatic bearings. Problem. The analysis of materials associated with the bench tests of sealing and bearing units revealed that practically no work is being conducted in this direction. Therefore, the need has arisen to create a universal stand that allows carrying out full-scale tests of sealing and bearing units of various types. This will also allow solving the problems of studying these objects when designing the prototypes. Goal. The goal is creation of new technological equipment that makes possible to carry out research and development of sealing and bearing units of compressor machines at the stage of working design for the purpose of verifying structural solutions, and also the analysis of their operability in the so-called parametric tests (after planned mainte-nance). Methodology. During operation irreversible changes occur in the design of compressors and tur-bo-compressors associated with the deterioration of the technical state of their structures, which cause permanent or sudden failures. Therefore, timely adjustment of the functional parameters of these units will make possible to obtain a significant fuel economy and ensure the operation of the units at the level of the calculated parameters. Results. A stand for full-scale inspection of sealing and bearing units of compressor machines was developed, a model stand was created, and a complex of studies of the dynamic sealing performance was carried out. The stand equipment and the monitoring equipment were chosen. Practical value. The proposed stand will allow investigating and bringing sealing and bearing units both at the stage of working design for the purpose of testing structural solutions and at the post-repair maintenance stage (checking the operability of the assemblies to be repaired and, if necessary, adjusting them).

Aurelian Virgil BALUTA

The life of companies, including the aerospace companies, depends on the business cycle. The paper presents the trends of law in ascending and descending period of the business cycle. A point of the paper is the separation of military and civil law in aerospace, public and private law, national and corporate security systems. Also the laws to be apply in relation with public authorities, private organizations, citizens are approched. In the paper are included some keys for interpretation such as the hierarchy of social values. In modern times, the humans life, rights and property must be the main protected values. The paper shows the methods to be accepted for the analyse/analysis of law in aerospace field: logical analysis, hystorical method, comparative method, social research, experimental method. In the aerospace field each of them has some particularities. The classification of laws depending of economic impact in the aerospace field is an other section. There are presented implications on cost, income, receipts, payments, duration of the activities, other restrictions.

Flávio Rodrigues Chaves, José Carlos Góis

The experimental results of specific heat capacity of 2 plastic bonded explosives formulations based on 1,3,5-trinitroperhydro-1,3,5-triazine, using differential scanning calorimetry thermal analysis, and the theoretical ones calculated with the specific heat capacity and mass fraction of individual compounds are compared for a temperature range between 340 and 410 K. Apart the filler, the plastic bonded explosives composition includes the binder based on hydroxyl-terminated polybutadiene, the plasticizer bis (2-ethylhexyl) sebacate and the curing agent isophorone diisocyanate. The experimental and theoretical results showed a better approach when no curing agent is added. Without curing agent, the specific heat capacity of plastic bonded explosives increases linearly with temperature. When plastic bonded explosive is cured, the specific heat capacity is nearly constant until 380 K and decreases linearly for higher temperature values. These results suggest that phase change requires adjusting parameters to different heating rates in order to describe adequately the experimental data.

Antônio Tomaz, Joaquim J. Barroso, Ugur Cem Hasar

Through electromagnetic simulation, the present work reports on a comparative study of the enhanced radiation properties of a standard X-band horn antenna loaded by a wire medium. Acting as an artificial dielectric the wire medium consists of an array of parallel metallic wires installed into the antenna with the wires oriented in the direction of the incident electric field. As compared with the properties of the empty antenna, the wire-medium antenna produces appreciable reduction in the side-lobe levels with an improvement of 10 dB at 8.87 GHz in the first side lobe. For the wire-medium antenna, the E- and H-planes look similar, a property desired for precision radar and radiometric mapping systems.

Gueorgi Smirnov, Antônio Fernando Bertachini Almeida Prado

The role of small inexpensive satellites continuously grows in the modern space exploration. Their use can significantly reduce the cost of the mission. However, the control of such satellites is a challenge. One of the major issues here is that such satellites usually do not possess a complex attitude control system, and three-axis stabilization might be unavailable. As a consequence, the thrust vector of the orbit control system cannot be arbitrary oriented in space and rather involved mathematical methods are needed in order to compensate the control system’s simplicity.

Ion FUIOREA

The paper deals with the extension of isotropic plates problem to the case of composite plates. In order to perform it, the Kirchhoff-Love hypotheses were “softened” by some additional ones. Considering the constitutive laws for composite materials the stress functions were eliminated by using Cauchy equations. As a result a partial derivative equation in displacements was obtained. Finally the boundary condition formulation was extended for the case of complex composite plates.