Aerospace Systems最新文献

This paper introduces the current and new Satellite solutions for local and global tracking of ships for enhanced Ship Traffic Control (STC) and Ship Traffic Management (STM) at sea, in sea passages, approaching to the anchorages and inside of seaports. All transportation systems and especially for maritime applications require far more sophisticated technology solutions, networks and onboard equipment for modern Satellite ship tracking than current standalone the US Global Positioning System (GPS) or Russian Global Navigation Satellite System (GLONAS) networks. The forthcoming Global Ship Tracking (GST), Satellite Data Link (SDL), Maritime GNSS Augmentation SDL (GASDL) and Maritime Satellite Automatic Dependent Surveillance-Broadcast (SADS-B) networks with Space and Ground Segment infrastructures for all three systems are discussed including benefits of these new technologies and solution for improved STC.

Stratospheric airships are a type of large aircraft capable of operating for extended periods in the stratosphere. This paper focuses on real-time trajectory planning for stratospheric airships. It constructs an optimization path dataset based on the Gauss pseudospectral method and utilizes deep learning neural networks to solve the real-time path planning problem for stratospheric airships. The article first establishes a six-degree-of-freedom airship spatial motion model. It uses the Gauss pseudospectral method to transform the original optimization problem into a parameter optimization problem, which is then solved using sequential quadratic programming. During the ascent phase, based on the airship's speed, yaw angle, and pitch angle when transitioning from the troposphere to the stratosphere, a total of 26,901 optimized paths are generated using the Gauss pseudospectral method, and the influence of different initial states on the optimized paths is analyzed. During the level flight phase, 3960 optimized paths are generated based on different initial speeds and yaw angles, and an analysis of the impact of the initial yaw angle on the optimized paths is conducted. Finally, the dataset generated by the Gauss pseudospectral method is divided into training and testing sets. Long short-term memory (LSTM) networks and Transformer networks are employed to learn and generate optimized paths from the dataset. Comparison results show that the neural network model is highly consistent with the optimized paths obtained using the Gauss pseudospectral method. Furthermore, the path generation time is reduced from hundreds of seconds to seconds, leading to a significant improvement in generation time stability.

The Engine Bleed Air system is a critical component in aircraft operations, providing necessary air supply for various onboard systems. Failures in the Engine Bleed Air (EBA) System can lead to flight delays, extended downtime, and safety risks. The current practice of using fixed pressure thresholds for EBA monitoring has limitations in terms of maintenance efficiency and aircraft safety. This paper presents a data-driven approach to dynamic thresholding and health index construction for the Airbus A330 EBA. A substantial EBA flight dataset is constructed using Quick Access Recorder (QAR) data, incorporating normal and faulty states. To explore the extensive QAR data of the EBA system, a data-driven baseline mining model is proposed in this study. To efficiently process high-dimensional feature data and model the pressure baseline, the LightGBM tree-based algorithm is employed. Additionally, this study proposes a health index (HI) construction method based on the baseline model, along with the EBA diagnosis and prognosis experiments based on the HI index. The Diagnosis and Prognosis methods, utilizing the proposed HI, demonstrate superior diagnostic effectiveness compared to fixed threshold methods and uncover a clearer trend of EBA health degradation. These contributions highlight the potential of data-driven approaches in managing aircraft EBA systems, emphasizing the advantages of dynamic thresholds and health index models for improved diagnosis and prognosis.

The major problem with the Scramjet engine is the starting and unstarting conditions, which depend on intake performance. Although the engine starts efficiently at designed conditions without any problem, at off-design conditions, due to misalignment of shocks, not satisfying either shock on the lip or shock on the shoulder and this leads to spillage flow and loss of total pressure. The intake design is modified to satisfy shock on shoulder condition to improve the operating range of the scramjet engine. Using ANSYS Fluent, Inviscid flow simulations are carried on modified design, it satisfied the shock-on-shoulder requirement, but in viscous simulations, the flow leads to unstarting conditions because of shock wave interaction with the boundary layer. Thus, shock on shoulder can be neglected in the design of hypersonic intake for scramjet engines. This paper analyzes a two-ramp, two-dimensional scramjet intake design using ANSYS Fluent. An elaborative CFD analysis was performed to estimate the efficiency of the hypersonic intake isolator because of changes in the flight conditions concerning free-stream conditions such as Mach number, angle of attack, and real-flow atmospheric conditions concerning altitude. This analysis shows that performance parameters such as total pressure recovery decreases during off design conditions. However, the normalized pressure ratio increases from 19 at Mach 4 to 72 at Mach 8. Due to an increase in the angle of attack, there is a increase in the pressure ratio and decrease in total pressure recovery. The flow separation bubble size increases as the Mach number increases leading to unstarting condition and increases as the angle of attack increases. An injection technique is used to suppress the flow separation. Out of the various orifices analysed the research concludes diamond shape injectors at 45° angle with total Nine injectors for mass flow rate not greater than 4% of intake mass flow satisfying all the performance parameters has reduced the flow separation bubble size from 4 mm to 0.95 mm in hypersonic intakes of Scramjet Engine at Mach 5.

Given the complex flight mission and structural characteristics of special-shaped tanks in new-generation space vehicles, this study investigates the sloshing characteristics and suppression methods of liquid propellant. Initially, the numerical calculation and structural suppression approaches for liquid propellant periodic sloshing are introduced. Subsequently, a new equivalent dynamic analysis approach based on the Volume of Fluid (VOF) method is presented and validated to simulate liquid sloshing and determine dynamic characteristic parameters such as sloshing mass, frequency, and damping ratio. Furthermore, anti-sloshing baffles are designed for sloshing suppression, and the influence of baffle height on sloshing frequency and damping ratio is examined. These significant findings provide crucial references and foundations for enhancing the flight stability and reliability of the attitude control system in new-generation space vehicles.

As the use of composite materials in aerospace is growing fast, more metal-composite hybrid structures come into being and thermal stress becomes increasingly a concern that may affect structural safety. In this paper, experimental and numerical studies are conducted on the mechanical strain induced by thermal stress in an AL/CFRP hybrid structure subjected to a heating–cooling–heating cycle. The studied hybrid structure consists of a metal plate and a composite laminate fastened by three bolts. The experimental results show that the mechanical strain in either metal or composite exhibits a hysteresis as the structure undergoes the temperature cycle, which implies the existence of structural nonlinearities. Finite element analysis, which incorporates details of the bolt joint, reproduces the hysteretic responses that reach a reasonable agreement with the experimental ones. Numerical studies disclose the effects of the structural parameters, i.e., friction coefficient, clamping force, fastener-hole clearance and bolt spacing, on the hysteresis and provide insights into the physical events during the thermal cycling. The reported work reveals that the movement of the bolts inside the surrounding holes is the key mechanism that drives the hysteretic thermal stress in the tested structure and sheds light on further investigations of structural safety of such hybrid structures under cyclic thermomechanical conditions.

This paper aims to create an effective flight controller that can reject severe disturbances, improving accuracy and efficiency. Current UAV control research fails to reduce large external disturbances. Integrating Linear Quadratic Regulator and Extremum Seeking Control helps overcome these negative influences. This paper describes a novel controller that stabilizes UAV output responses and handles external disturbances. Linear Quadratic Regulator is used to stabilize and control the UAV under optimal flight conditions, whereas Extremum Seeking Control is utilized to counteract external disturbances. The recommended flight controller is compared to the Linear Quadratic Gaussian Regulator, which uses the Kalman Filter to reduce disturbances. This comparison analysis demonstrates our method's superiority. In addition, the UAV's pitch and yaw angles experience aggressive maneuver motions to test the controller. The proposed strategy reduces noise and harsh disturbances including step, ramp, and sinusoidal variables during agile maneuvers. This study defines disturbances as follows: External noise in control systems is random signal variations generated by external disturbance; Step disturbances are fast, long-lasting system signal changes; ramp disturbances are sluggish; and sinusoidal disturbances are periodic oscillations. These disturbances make system stability and functionality difficult. Since our control strategy reduces disturbances, the recommended method can adapt system output to random fluctuations, rapid changes, gradual changes, and periodic oscillations. Linear Quadratic Gaussian Regulator is able to reduce noise from the system's output, but it fails to produce satisfactory results during major disturbances. The proposed method, however, is unique since it develops a controller with advanced disturbance rejection capabilities.

In this study, the commercially available CFD software ANSYS-Fluent is used to conduct a three-dimensional unsteady-state analysis of the aerodynamic coefficients of an ejection seat system. The aerodynamic coefficients are calculated by solving Reynolds-averaged Navier–Stokes equations. ANSYS meshing software is utilized to create an unstructured grid of tetrahedral cells for this analysis. The validation of the numerical methodology is performed initially on a sphere at subsonic Mach number (Ma) for different Reynolds numbers (Re) before the validation of the ejection seat system. The computed unsteady-state results are compared with the experimental and available numerical results for both the sphere and the ejection seat. Later the aerodynamic coefficients of the ejection seat are further investigated at Ma = 0.7 by changing the angle of attack (α) and yaw angle (β). The findings of this study show that the magnitude of the axial force coefficient (C_X) and values of the side force coefficient (C_Y), normal force coefficient (C_Z), pitching moment coefficient (C_m), yawing moment coefficient (C_n), and rolling moment coefficient (C_l) changes with the variation of the α and β.

With the development of artificial intelligence and information technology, drones working in tandem with manned aerial vehicle have become the new normal. Current paper focuses on the following theme: how to assess the effectiveness of manned/unmanned aerial vehicle systems under different formations. However, the analysis of the effectiveness of manned/unmanned aircraft cooperation faces the problem of unclear mechanisms and difficulty in tracing the key influencing factors. Therefore, in this paper, a closed frequent pattern mining method is used to analyze and design a new data structure based on cross-linked table improvement. In this paper, the units and capabilities in the manned/unmanned aerial vehicle system are mined and analyzed in a time-series manner to obtain the effectiveness of the patterns of manned/unmanned aircraft utilization in tandem under different formations. Finally, a typical maritime application scenario is used as an example to effectively compare the effectiveness of different manned/unmanned aircraft cooperative modes and to provide guidance for the subsequent development of manned/unmanned aircraft cooperative applications.

Electronic Warfare is a type of military operation that uses electromagnetic radiation to identify, exploit, limit, or prohibit the use of the electromagnetic spectrum. The main objective of this paper is to improve the range resolution of multiple targets in Electronic Warfare systems under noisy conditions. Multiple Signal Classification (MUSIC), a high-resolution algorithm is used with denoising techniques to enhance the ability of digital receivers to detect multiple targets. The Savitzky Golay filter is used in the first stage as a pre-processing filter, and the novel noise removal technique is used in the second stage to achieve better target detection and discrimination. This modification to the MUSIC algorithm aims to address its limitations in the presence of noise and when targets are in proximity, resulting in improved performance in Electronic Warfare scenarios. Using the proposed method, we are able to detect three (3) target frequencies up to SNR of − 12 dB and four (4) target frequencies up to SNR of − 19 dB, with the percentage of error in the estimation of frequency is 0.58%. The optimized computation complexity is highlighted as a strength, making the proposed method more efficient compared to alternative approaches.