Aerospace Systems最新文献

Space exploration demands robust spacecraft(SC) subsystems to endure the harsh conditions of space and ensure mission success. Attitude determination and control subsystems (ADCS), as a significant subsystem within SC, are essential for providing the necessary pointing accuracy and stability, and failures in the ADCS can lead to mission failure. Therefore, robust design, thorough testing, and Fault Detection, Isolation and Identification(FDII) techniques are crucial for spacecraft operations. This paper focuses on developing advanced FDII techniques for reaction wheels(RW) within ADCS, evaluating the Prony-based FDII technique for RW, considering its accuracy, time complexity, and memory usage, and Additionally, it introduces new machine learning-based FDII techniques, including enhancements to the Prony-based FDII technique, to manage single faults more effectively. The new proposed techniques used to explore the novel area of multiple faults within the same subsystem. Results indicate that the proposed FDII techniques significantly improve fault detection accuracy, isolation time, and memory efficiency compared to traditional techniques. These advancements enhance the reliability and longevity of spacecraft missions, ensuring that critical subsystems like ADCS operate effectively in the challenging conditions of space. The contributions presented in the paper are introducing three different FDII machine learning-based techniques that support identifying five types of single faults in spacecraft ADCS RW, outperform the Prony-based FDII technique for spacecraft ADCS RW in terms of time and memory complexity, and Finally, improves the fault tolerance of the spacecraft system by detecting Multiple fault combinations that may occur at the same time in one system.

A comprehensive simulation model is established to design the altitude adjustment of the stratospheric airship with the application of the adjustable ballonets for pitch control. A series of mathematical models, including atmosphere, thermal, dynamics and kinematics, airship pressure and pitch control, are developed to achieve the altitude adjustment when the stratospheric airship flying at the stationary phase. The altitude adjustment strategy takes the thermodynamics, dynamics, and pressure control requirements together into consideration, to better fulfill the realistic flight conditions. Based on these models, the characteristics of stratospheric airship’s flight performance are simulated and discussed in detail. The results show that taking adjustable ballonets as the actuator can realize the pitch and pressure control simultaneously and satisfy the requirements of the flight missions. Furthermore, stratospheric airship can achieve altitude adjustment with the application of adjustable ballonets and propulsion system coordinately. Moreover, the simulation model can accurately present the interaction of thermodynamics, pressure, and dynamics, which better satisfies the realistic flight situation. The results and conclusions presented herein contribute to the design and operation of stratospheric airship.

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.

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.

Digital Image Correlation (DIC) is a vital optical measurement technique that finds diverse applications in the domain of mechanics of materials. In aerospace applications, DIC has excellent scope in structural health monitoring of aircraft components. Aircraft wings, one of the critical components are subjected to different loads during flight. Ground testing and In-flight testing of wings can benefit substantially by DIC monitoring. DIC can be utilized to analyze the time-based variation in the speckle pattern or grid, applied to the wing’s surface. High-resolution images processed through a suitable correlation software helps decipher the data into stress and strain contours. Thus, any potential material failure or component defects can be identified. DIC also finds a role in flutter analysis, enabling the scrutiny of wing vibrations and deformations. In this review, the applications of DIC in analysis of aircraft components has been taken up, as in-flight structural health monitoring is a critical activity for a safe flight.

The stability criteria of any fin-stabilized flying object are a decisive metric in evaluating its overall performance and results in mission success. Flight stability depends on many parameters such as body configuration, the center of gravity location, atmospheric conditions, and flight manoeuvres. These manoeuvres are needed for better target interception especially for moving targets located at short ranges, resulting in high frequencies either in pitch or yaw directions. This study examines the impact of body pitch frequency on the stability of a supersonic fin-stabilized object. Time-dependent numerical simulations are implemented to model the unsteady flow field induced by a simple harmonic motion in the case study missile. The missile’s tail section dominates the lift force generated compared to the forebody, resulting in a downstream shift of the missile’s center of pressure and, consequently, an increase in the static stability margin as the pitching frequency increases. However, pitch-damp aerodynamic derivatives remain unchanged at various pitching frequencies, indicating frequency independence. The validity of the results is confirmed compared with wind tunnel data.

This article presents the synthesis of a dynamic output feedback controller for a satellite orbital system confronted with uncertainties. The investigated method transforms the closed-loop system, synthesized by the controller, into an (alpha )-strictly negative-imaginary system. It utilizes the DC-loop gain condition associated with negative-imaginary systems theory to demonstrate robust stability of the satellite orbital system in the presence of uncertainties. Furthermore, the synthesized negative-imaginary closed-loop system exhibits notable time-domain performance. The numerical simulation outcomes presented in this article validate the investigated synthesis method.