Aerospace Systems最新文献

To address the scheduling challenges of mixed regional missions with different priorities across multiple observation modes of the SAR satellite, this study presents a Hierarchical Adaptive Scheduling Method (HASM) for generating optimized booting and imaging commands that align with diverse application requirements. First, considering spaceborne storage and energy limitations, a weighted multi-objective optimization model, incorporating mission decomposition and scheduling, is developed to enhance the flexibility of imaging strip segmentation and insertion. The weighted objective function is designed to balance the prioritization of urgent targets, the rapid increase of revenues, and the optimal utilization of resources. Meanwhile, the HASM method is proposed to alleviate the complexity and computational burden of high-dimensional combinatorial optimization problems. Furthermore, hyperparameters are automatically configured through observation pattern selection and optimal weight determination methods to minimize the overall mission observation time. Finally, simulation results demonstrate that the proposed method enhances the efficiency of over 95% of missions in global multi-mode mixed mission scheduling, while reducing the overall coverage time by more than 20% for China’s multi-priority missions.

For large precision aircraft structures, the main method of obtaining the dynamic characteristics of the structure is modal testing. The most important step in modal testing is to find a set of optimal excitation forces with appropriate distribution and amplitude to obtain the normal modal of the structure. Most of the existing methods for adjusting the excitation force rely on the experience of the researchers, with problems of time-consuming and insufficient accuracy in obtaining the modal parameters. This paper proposes a hybrid automatic force adjustment method in normal modal testing of structures which can solve the problem of force adjustment in dense mode. This method firstly measures the frequency response function of the structure, identifies the modal parameters through the polyreference least squares complex frequency domain method (PolyMAX), then use these modal parameters as the initial value of the normal modal test to derive the initial optimal excitation force. Finally, the optimal excitation force and the corresponding modal parameters are obtained by frequency sweep and particle swarm algorithm. Result shows that the method proposed in this paper can effectively solve the problem of local optimal and insufficient indicator function, and can reduce the force adjustment time of normal modal tests for large precision structures and improve the force adjustment accuracy.

In this paper, a data-driven adaptive dynamic programming method is proposed to solve the thrust tracking control problem of a turbofan engine with unknown system dynamics. Firstly, the augmented system of the engine and the reference signal system is established. The thrust tracking problem can be transformed into an optimal control problem by this augmented system. Secondly, an augmented algebraic Riccati equation is derived under the performance index of the original dynamics, and an offline policy iteration method is design to solve the optimal thrust tracking problem. Thirdly, a new online data-driven adaptive dynamic programming method is proposed to solve the optimal thrust tracking problem when the engine dynamics is inaccessible. Finally, some numerical simulation results are given to demonstrate the effectiveness of the proposed method.

This paper presents a morphing missile with an expandable flared skirt, which aims to change aerodynamic shape according to the change of flight environment to improve flight efficiency. The morphing missile with an expandable flared skirt is regarded as a multi-rigid-body system, and the six-degree-of-freedom(6-DOF) nonlinear dynamic model of the missile is established considering the changes of aerodynamic force, mass distribution, and inertia characteristics during morphing. In order to investigate the longitudinal dynamic characteristics of the missile, the nonlinear dynamic model is de-coupled to obtain its longitudinal motion equation. The aerodynamic parameters of the missile in the whole flight state envelope are simulated by quasi-steady assumption, and the aerodynamic coefficients under different flight environments and flared opening angles are obtained. The aerodynamic coefficients obtained from the simulation at each operating point are fitted to the flight altitude, Mach number, and the morphing rate of the flared skirt by the least square method. Finally, the parametric model of the aerodynamic coefficients is obtained. Finally, the aerodynamic coefficient function model is introduced into the longitudinal motion equation of the missile, and the longitudinal dynamic characteristics of the missile in different flight conditions are obtained by numerical simulation. The simulation results show that the morph of the flared skirt has a significant influence on the longitudinal motion characteristics of the missile.

Ballistic missiles are perhaps the most critical and common flying devices today, flying at very high altitudes compared to aeroplanes. Among the important points about these flying devices is their very high speed in the final phase, usually several times the speed of sound. Choosing essential design parameters for making these devices has always been a significant challenge for designers. Structural, propulsion, aerodynamic, and control parameters are the most influential. The topic of nose cone aerodynamics is one of the essential design components to achieve the most reliable and optimal designs. Deciding the right nose cone has been one of the main challenges in recent years in this field. This article aims to review and analyse some examples of standard nose cones with this structure. For this purpose, first, the arrangement and layout of various designs and their specifications have been presented. The nose cone modelling has been performed for all modes, and each layout's results have been introduced. Finally, a model based on the results is proposed, the most optimal and reliable arrangement based on aerodynamic parameters.

Underwater target detection is a critical and rapidly evolving research area with significant applications in both military and civilian fields. Multi-Beam Forward-Looking Sonar (MFLS) operates reliably in low-visibility conditions and is one of the most widely used technologies for underwater detection. However, the complex and dynamic underwater environment, signal attenuation and distortion, along with the high cost of signal acquisition and transmission, make MFLS images detection one of the most challenging tasks in computer vision and image processing. To address these challenges, this paper proposes a target detection model based on MFLS, named AGD-YOLO. First, the ADNet attention mechanism is introduced to enhance performance by focusing on relevant features while suppressing unrelated noise. This denoising mechanism balances efficiency and further improves the model’s detection performance. Second, MPDIoU is adopted as the boundary regression loss, which considers the overlapping region, center point distance, and deviations in width and height, thereby enhancing the efficiency and accuracy of bounding box regression. Third, a new dataset based on MFLS is constructed to facilitate the detection of Unmanned Underwater Vehicle (UUV). Experimental results show that the proposed model improves ({mAP}_{0.5:0.95}) by 2.6% compared to the second-best detection algorithm, significantly enhancing detection performance on MFLS images.

This paper investigates the evolution properties of the flow field structure for axial descent rotor based on the unsteady momentum source method combined with the Computational Fluid Dynamics (CFD). The study focuses on analyzing the speed critical value during the onset of or exit from the Vortex Ring State (VRS), and its changing characteristics of the flow field structure. Results from the Lagrangian Coherent Structure (LCS) analysis reveal the switch particularity between the tubular slipstream and the annular vortex, suggesting the criticality change character on flow field structure which occurs in the evolution process of VRS. These criticality features, that is the VRS boundaries described by the flow structure change, as determined by this method, are consistent with the existing theoretical and experimental results, verifying the feasibility of the established analysis method in the study of such boundaries. This work provides a robust framework for studying VRS boundaries and offers insights for further research on the underlying flow mechanism.

Predicting hard landings is crucial for aiding pilots’ decisions and ensuring flight safety. This paper addresses the limitations of current hard landing prediction models, specifically in terms of long-term forecasting accuracy and explainability. To overcome these challenges, it introduces the Informer hard landing prediction model, developed using QAR data, and performs an in-depth explainability analysis of the model’s output. Following the principles of learning assurance, the data processing and model training phases are standardized. This involves the application of forward–backward filtering and Granger causality testing to refine the QAR data, thus creating a dataset that aligns with essential prediction standards. The Informer model addresses the challenges of multivariate time series discontinuities by localizing its network to enhance data adaptability. During model training and testing, hyperparameters are finely tuned to maximize prediction accuracy and generalizability. To improve transparency, the model employs an attention weight matrix and a feature reset-based explainability method. Tests show that models trained on datasets developed through a defined data management process deliver favorable predictive performance. The localized enhanced network improved prediction accuracy by 23.5% and increased its capacity to learn from discontinuous multivariate time series. Compared to the LSTM network, the Informer network achieved an 18.83% improvement in prediction accuracy and demonstrated superior long-time series prediction capabilities.

There are about 1,900 electrical measuring equipment in the aircraft assembly workshop and aircraft production line, which is directly related to the manufacturing quality of the aircraft. This paper evaluates the health status of electrical measuring equipment based on Analytical Hierarchy Process. The bottom-up health status evaluation system of electrical measuring equipment is established by selecting an appropriate number of health indicators. According to the failure mode summary of electrical measuring equipment, the evaluation indexes at all levels are determined, the health assessment and judgment matrix of electrical measuring equipment is constructed. The 1–9 scale method is used for quantitative analysis of the indexes of electrical measuring equipment. The health level of the electrical measuring equipment is divided into 5 levels, and the corresponding relationship between the score of the measuring equipment and the health status is formulated. The 0–1 method and fuzzy distribution method are used to score each quantitative index. The historical data of a company electrical measuring equipment is used for example analysis, and the example results show that the calculation results of the health status score of the general measuring equipment is 0.951. The health status of the general measuring equipment is health. The health status score of the special measurement equipment is 0.877. The health status of the aviation specific measuring equipment is available.

The paper develops and investigates various options for separating the first and second stages of a promising launch vehicle without using pyrotechnic elements (such as the “Clamp Band” type, “petal” and “ball” types). A review and analysis of the applicability of pyrotechnic elements as part of separation devices of existing and promising launch vehicles was carried out, as a result, it was revealed that their use is difficult for technological reasons related to the need for specialized devices and equipment for accurate control of the detonation process and the likelihood of a large number of fragments and shock loads during operation, which negatively affects the provision of specified structural and operational characteristics of launch vehicles. The basic requirements for ensuring the rational operation of the proposed separation devices, taking into account the possibility of their multiple use, are considered. Experimental and mathematical modeling of relative motion of the stages separating according to the “cold” scheme under the influence of static and dynamic loads has been carried out, and rational technical solutions and design and technological approaches for the proposed separation devices have been selected. The results of the research on assessment of the stress–strain state of structural elements of the proposed separation devices without using pyrotechnic elements in various configurations, as well as their novelty, are presented.