Abstract:In the fields of intelligent manufacturing, aerospace, and robotics, control systems often operate under unknown dynamics. This significantly limits the effectiveness of traditional model-based control methods. Reinforcement learning (RL), as a data-driven intelligent control approach, enables policy learning and optimization through interaction with the environment, showing great potential for solving optimal control problems in such model-unknown scenarios. This survey focuses on the issue of unknown dynamic models in continuous-time systems and first reviews the development of general reinforcement learning algorithms and their application in model-known scenarios through industrial examples and theoretical analysis methods. It also summarizes representative methods for model-unknown scenarios, such as model-based RL, off-policy integral RL, and Q-learning approaches. The survey also introduces Lyapunov-based theoretical analysis tools and important assumptions. It discusses cutting-edge topics such as RL under partial observability using large language models, safe RL, and stability and robustness enhanced RL, while highlighting the challenges faced by existing methods.

Abstract:Absolute gravity measurement based on laser interferometry is the main means to establish gravity measurement reference, and it is also the gravity reference instrument used currently. In recent years, along with the development of quantum absolute gravity measurement techniques, new opportunities have been presented for establishing a gravity reference with higher accuracy. With the support of the National Development and Reform Commission, Huazhong University of Science and Technology had established the “precision gravity measurement facility (PGMF)” as a major national scientific and technological infrastructure. A key component of this facility's construction is the establishment of a micro-Gal level absolute gravity measurement reference station. This station provides a standardized reference for gravity measurement instruments and data, serving as a foundation for achieving high-precision measurements and applications in the gravitational field. High-precision gravity measurement instruments are the core equipment for PGMF to achieve gravity measurement reference. For this purpose, PGMF independently developed a reference quantum absolute gravimeter suitable for station measurement and a miniaturized quantum gravimeter for reference extension. Furthermore, a gravity comparison field and a background physical environment monitoring system were established. Ultimately, a micro-Gal level gravity measurement reference station was established.

Abstract:Addressing the critical need for autonomous navigation of low-altitude unmanned aerial vehicles (UAVs) in Global Navigation Satellite System (GNSS)-denied environments, this paper presents a comprehensive survey on absolute visual localization techniques based on a "retrieval-matching-pose estimation" framework. It begins by analyzing the challenges inherent to low-altitude UAV observation, such as significant imaging disparities, rapid scene scale variations, and object occlusions, there by elucidating the advantages of the hier-archical framework for large-scale, long-endurance localization tasks. Subsequently, the review systematically examines the technological evolution and current state-of-the-art across three core components: cross-view image retrieval, pixel-level feature matching, and UAV pose estimation, tracing the progression from traditional handcrafted features to deep learning paradigms. Finally, considering the requirements for deployment on airborne edge-computing platforms, the paper discusses the limitations of existing technologies and outlines promising future research directions. This survey is intended to serve as a valuable reference for both research and practical applications in absolute visual localization for low-altitude UAVs.

Abstract:Currently, countries around the world are generally unable to defend effectively against high-speed vehicles, and related basic research is still in its infancy. Accelerating the development of high-speed target defense technology is crucial for maintaining aerospace security. Given the problems present in the near-space defense confrontation under this background, such as a narrow defensive posture, significant speed disadvantages, and limited single-missile defense capability, this paper reviews the current development status of the defense guidance law for high-speed near-space vehicles. It analyzes the deficiencies of the existing guidance law research from perspectives such as complex offensive and defensive confrontation scenarios, missile cooperative guidance mechanisms, and real environment effectiveness constraints. It also foresees the key development directions of future defense guidance laws for high-speed vehicles, aiming to offer references for the construction of future defense systems for high-speed vehicles and the frontier basic research in the field of precision guidance.

Abstract:During the high-speed flight of aircraft, raindrop impact erosion causes significant damage to surface materials, thereby seriously affecting flight performance and structural safety. This paper aims to systematically review the mechanical mechanisms, key influencing factors, and progress in corresponding protection technologies of high-speed raindrop impact erosion. In terms of experiments, current studies mainly rely on devices such as wind tunnels, rocket sleds, and rotating arms to construct simulated environments of real rain fields. Meanwhile, high-speed photography is used to record the dynamic erosion process, and laser velocimetry is employed to obtain raindrop impact velocity, thus achieving multi-dimensional observation of erosion behavior. In terms of numerical simulation, this paper focuses on introducing mainstream simulation techniques such as the finite element method (FEM) and the smoothed particle hydrodynamics (SPH) method. Additionally, an overview was provided of existing research methods and outcomes, which primarily involve establishing liquid-solid coupling models to analyze the propagation patterns of stress waves and the dynamic response characteristics of materials during impact processes. The research results show that raindrop impact velocity, impact angle, and mechanical properties of materials are the key factors affecting the erosion rate. Based on the actual flight envelope parameters of aircraft, targeted optimization design of rain erosion resistance performance can be carried out, which provides a theoretical basis and technical support for improving the service safety of aircraft in harsh meteorological environments.

Abstract:The aerodynamic environment in low-altitude regionsis characterised by complex flow field structures, diverse disturbance sources, and significant coupling effects. These factors have a significant impact on the aerodynamic performance and flight safety of unmanned aerial vehicles(UAVs), making them a key focus of research in the field of low-altitude UAV aerodynamics. Three typical scenarios have been systematical reviewed: complex low-altitude wind fields, spatially constrained environments, and multi-UAV environments. The fundamental characteristics and modelling approaches of complex low-altitude wind fields have been systematically outlined, and their effects on UAVs and key research methodologies have been summarised. Spatially constrained environments are categorised based on disturbance mechanisms and constraint types, and the review provides a comprehensive summary of the aerodynamic impacts on UAVs within such environments. Spatially constrained environments are categorised based on disturbance mechanisms and constraint types, and a comprehensive summary of the aerodynamic impacts on UAVs within such environments has been provided. The aerodynamic characteristics of UAVs in multi-UAV environments have been summarised, and the aerodynamic coupling mechanisms and research methodologies for cooperative and non-formation flight scenarios have been outlined. Building upon this foundation, the core issues and key challenges currently facing aerodynamic research on UAVs in low-altitude environments have been further refined, and future research priorities in this field have been outlined.

Abstract:This paper presents a review of model predictive control and its applications in aircraft systems. Starting from representative mission scenarios and key technical challenges, it clarifies the design requirements for aircraft control systems. In response to the design needs of different classes of vehicles, the review surveys and synthesizes a coherent framework for model predictive control. It traces the origins and development of model predictive control and summarizes its theoretical foundations, with particular attention to robust model predictive control, Lyapunov-based model predictive control, switched model predictive control, and explicit model predictive control, thereby delineating the principal advances reported in recent years. Building on this framework, the paper examines applications of model predictive control to quadrotors, helicopters, fixed-wing aircraft, and high-speed aircraft. Finally, it outlines future research directions for model predictive control in aerospace control and offers concluding remarks.

Abstract:With the increasing number of space activities, HVI (hypervelocity impacts) caused by space debris and micrometeoroids have become a major threat to the safety of spacecraft in orbit. Such collisions not only result in mechanical damage but also generate plasma, whose electromagnetic effects pose severe risks to highly integrated spacecraft electronic systems. A systematic review of plasma physical effects induced by hypervelocity impacts is provided. The review covered the mechanisms of plasma generation, kinetic characteristics, electromagnetic radiation, and induced discharge, encompassing both theoretical and experimental progress. Special emphasis was placed on the introduction of condensed-phase products (dust grains) in hypervelocity impacts and the resulting dusty plasma effects. This review aims to offer researchers in the field a comprehensive literature summary and to highlight key scientific questions and future research directions. Ultimately, it seeks to provide theoretical support for enhancing the survivability of spacecraft in orbit and for developing next-generation electromagnetic protection technologies.

Abstract:DFRC (dual-function radar-communication) is proposed to overcome spectrum conflicts, hardware redundancy, and electromagnetic compatibility bottlenecks inherent in traditional separated architectures through hardware resource sharing and isomorphic signal waveform design, whereby the integrated operational effectiveness and battlefield survivability of platforms are significantly enhanced. The evolution of DFRC technology from its conceptual inception, through architectural advancements, to system implementation was systematically reviewed. The DFRC waveform design methodologies based on mainstream signal schemes were analyzed emphatically, including linear frequency modulation, orthogonal frequency division multiplexing, and orthogonal time frequency space. Furthermore, various sensing-centric waveform design criteria were explored in depth, such as beampattern matching, Cramér-Rao bound minimization, information-theoretical design, and so on. The engineering roadmap from software-defined radio compatibility verification and airborne multimodal waveform fusion to multi-node and multi-domain cooperation was summarized, clearly illustrating the theoretical-to-practical transition of DFRC. Through presenting the complete technical evolution of the DFRC system from the conventional single-input single-output system to multiple-input multiple-output system, and then to the prototype demonstrations, this overview provides systematic theoretical guidance and practical references for future research and development of DFRC systems.

Abstract:In the current landscape of large-scale model training, the contradiction between the exponential growth of model parameters and the slow increase in GPU memory capacity has become increasingly prominent. Among memory optimization technologies, recomputation and computational offloading reduce GPU memory overhead by trading time for space. The development trends of recomputation and computational offloading are first analyzed in this article. Then, the hardware bandwidth bottlenecks and software ecosystem adaptation challenges faced by memory optimization are analyzed, with a focus on the heterogeneous architecture characteristics of domestic artificial intelligence platforms. It also delves into the memory optimization technologies for large model training on domestic platforms such as MT-3000, with the aim of providing technical references for large model training on domestic platforms.