It is known that the optimal LQR regulator (Linear Quadratic Regulator) with full state feedback has remarkable robustness properties, defined by gain margins of (1/2, ) and phase of at least ± 60 degrees. Representing a realistic approach to control synthesis, LQG (Linear Quadratic Gaussian) synthesis elegantly overcomes the difficulties of an unrealistic full output feedback synthesis LQR. LQG synthesis replaces the ideal case of complete feedback after the state by introducing a special, dynamic observer, the optimal Kalman estimator. LQG synthesis is considered the most powerful acquisition of automatic control science (i.e., control with feedback) which has a history of over 85 years. Unfortunately, LQG synthesis is not infallible either. In a famous article, John Doyle demonstrates that the LQG controller cannot guarantee any stability reserve. To counteract this shortcoming, thus appears the LQG/LTR method (Linear Gaussian Quadratic synthesis with Loop Transfer Recovery), in which the shape of the loop of the robust controller with full feedback after state LQR is restored/recovered, via certain specific procedures. This article shows that the LQG/LTR methodology can also lose its robustness. Therefore, our paper reveals a veritable dialectic of challenges: from LQR to LQG, from LQG to LQG/LTR, from LQG/LTR in search of a new, more efficient approach.
Lunar regolith is a thin layer of weakly cohesive detrital materials covering the lunar surface. Studies on returned lunar samples have revealed that the lunar regolith mainly consists of fragments of rocks, minerals, breccia, glasses, and agglutinates with a median grain size of ~40 to 800 μm. The lunar regolith was produced from the space weathering of lunar rocks, including the following processes: meteoritic bombardment, solar wind implantation, solar and galactic cosmic ray irradiation, and gardening. During space weathering, the maturity of the lunar regolith increases as the median particle size decreases, and specific minerals and structures (such as nano Fe0) are produced. The chemical and isotopic compositions of the lunar regolith also change via interactions with solar wind and cosmic rays. Volatiles resulting from solar wind, asteroid impacts, and volcanic degassing can be preserved in the lunar regolith and redistributed to the lunar polar regions during micrometeorite bombardment. Cosmic radiation can produce nuclides through spallation and neutron capture reactions, thereby changing the isotopic compositions of the lunar regolith, which could reflect the gardening history of the lunar regolith. Thus, the lunar regolith carries massive information about the space weathering history, impacting processes, and the interior of the Moon. In this review, we discuss the progress that has been made toward understanding the composition, the lateral and vertical structure, and the formation processes of the lunar regolith, in particular, the progress that has been made after the Chang’E mission series.
Motor vehicles. Aeronautics. Astronautics, Astronomy
In parallel with government policies being implemented internationally to reduce noise pollution along roads, improve automobile fuel efficiency to curb global warming, and reduce traffic accidents caused by slippage, there is a need to improve tire performance, which involves a trade-off between each of these factors: radiated noise, rolling resistance, and wet grip. To efficiently advance these research projects, it is necessary to utilize information on the latest research in this field from around the world. For this reason, the author conducted a literature survey.
A spin flight vehicle is characterized by its inherent active or passive spinning motion, resulting in complex movements that pose challenges for accurately calculating aerodynamic forces. This often leads to significant discrepancies between simulation results and actual performance. To address the low reliability of simulations for single-wing spin flight vehicles caused by difficulties in aerodynamic force estimation, this paper introduces the concept of an aerodynamic domain model. Based on the configuration of a specific single-wing spin flight vehicle, the model applies rigid body dynamics and uses blade element-momentum theory for aerodynamic calculations. By considering both relative and absolute error characteristics between actual and computed aerodynamic values, the aerodynamic domain model is established with explicit methods for determining error factor function bounds. The theoretical and practical value of the model is demonstrated through a simulation example, showing its ability to represent the range of true aerodynamic forces and moments experienced by the vehicle. This approach reduces the dependence on highly accurate aerodynamic calculations while maintaining engineering feasibility, enabling effective flight risk assessments within a specified range.
In recent years, tail-sitter unmanned aerial vehicles (UAVs), capable of vertical take-off and landing (VTOL) and long-range flight, have garnered extensive attention. However, the challenge of yaw control, particularly for large-scale UAVs, has become a significant obstacle. It is challenging to generate sufficient yaw moments by motor differential thrust without compromising control authority in other channels or increasing mechanical complexity. Therefore, this paper proposes the concept of blown yaw, which utilizes the high-velocity airflow over rudders, induced by the propellers slipstream, to enhance the yaw control torque actively. An over-actuated, hundred-kilogram-class, tail-sitter UAV is designed to validate the effectiveness of the proposed method. To address the control allocation problem introduced by the implementation of blown yaw, an optimization-based control allocation module is developed, capable of precisely mapping the required forces and torques to all actuators. The proposed method, combined with computational fluid dynamics (CFD) simulations, accounts for the propeller model and the significant differences in actuator effectiveness across various flight conditions. Simulation results demonstrate that the proposed blown-yaw method significantly enhances the yaw control performance, achieving an overall energy savings of approximately 8.0% and a 60% reduction in the mean-squared error. Furthermore, the method exhibits robust performance against variations in control parameters and external disturbances.
Low-Earth-Orbit (LEO) satellite networks have the advantage of global internet coverage and low latency, and they have enjoyed great success in the past few years. In LEO satellite networks, laser-based inter-satellite links (ISLs) are widely employed to achieve on-board data relay, and further to provide high-capacity backhaul worldwide. However, ISLs are prone to break due to the outage of the ISL capturing, tracking, and aiming systems. Meanwhile, breaks caused by different reasons can last from milliseconds to hours. The hybrid ISL fault leads to the on-board routing protocol to flap frequently, thus causing high routing overheads, low convergence speed, and degraded service consistency. In this work, we propose a hybrid fault detection mechanism to identify transient and long-term ISL outage. Further, for transient link outage, the segment routing-based loop-free backup path is adopted to provide real-time transmission recovery, and precise global route convergence is adopted to restore the long-term routing failure. For the inconsistent routing table switch between the phase from transient to long-term fault, we propose a dual timer mechanism to make sure the path can be smoothly switched without micro-loops. Simulation results validate the feasibility and efficiency of the proposed scheme.
This work investigates the pseudo-command restricted problem for tailless unmanned aerial vehicles with snake-shaped maneuver flight missions. The main challenge of designing such a pseudo-command restricted controller lies in the fact that the necessity of control allocation means it will be difficult to provide a precise envelope of pseudo-command to the flight controller; designing a compensation system to deal with insufficient capabilities beyond this envelope is another challenge. The envelope of pseudo-command can be expressed by attainable moment sets, which leave some open problems, such as how to obtain the attainable moment sets online and how to reduce the computational complexity of the algorithm, as well as how to ensure independent control allocation and the convexity of attainable moments sets. In this article, an innovative algorithm is proposed for the calculation of attainable moment sets, which can be implemented by fitting wind tunnel data into a function to solve the problems presented above. Furthermore, the algorithm is independent of control allocation and can be obtained online. Moreover, based on the above attainable moment sets algorithm, a flight performance assurance system is designed, which not only guarantees that the command is constrained within the envelope so that its behavior is more predictable, but also supports adaptive compensation for the pseudo-command restricted controller. Finally, the effectiveness of the AMS algorithm and the advantages of the pseudo-command restricted control system are validated through two sets of independent simulations.
Antonio Chiariello, Gaetano Perillo, Mauro Linari
et al.
This study addresses the crucial role of post-buckling behavior analysis in the structural design of composite aeronautical structures. Traditional engineering practices tend to result in oversized composite components, increasing structural weight. EASA AMC 20-29’s Building Block Approach suggests phased testing, but its time and cost challenges necessitate a shift to high-fidelity post-buckling analyses, exemplified by MSC NASTRAN SOL 400. This approach, showcased in the analysis of the Next Generation Civil Tilt Rotor Technology Demonstrator’s wing (NGTCTR-TD), effectively de-risks static tests, contributing to a more efficient certification process. The study demonstrates how advanced simulations provide detailed insights into local buckling phenomena, allowing precise stress distribution analysis. These analyses eliminate the risk of structural failure, paving the way for safer, more efficient, and cost-effective airframe structures. Future developments aim to validate numerical analyses with experimental data, further emphasizing the reliability and benefits of high-fidelity simulations.
The aerodynamic interference between the different components of quad-tiltrotor (QTR) aircraft were considered to analyze its influence on trim characteristics. A comprehensive method with the fixed-wake model was developed for multiple aerodynamic interactions, improving the accuracy of the flight dynamics analysis. Additionally, a more general control strategy was developed to tackle the redundant control issue of the QTR, improving its control efficiency by coordinating the authority relationship of various control surfaces across the flight range. Then, the trim features were calculated in the helicopter mode, conversion mode, and airplane mode, and the relevant results with and without interaction were compared. The results show that the aerodynamic interaction mainly influences the body’s vertical force, longitudinal force, and pitching moment. Furthermore, there are significant differences between collective and longitudinal sticks and pitch attitudes. The interference plays a major role in helicopter and conversion modes with a less-than-30-degree tilt angle.
Background. The need to ensure a high degree of product quality puts forward new requirements for
models, methods and tools for managing production processes and the quality of products. This is especially true for
the radio-electronic industry, where the effectiveness of technological innovations is dynamically confirmed during
the serial production of products. Materials and methods. The intellectualization of radio electronics production is fully
consistent with the concept of Industry 4.0 and the digitalization strategy. At the same time, quality assurance depends
on the effective implementation of a quality management system at the enterprise, which requires top management
not only to follow the requirements established in the GOST R ISO 9001-2015 standard, but also to take into
account the internal specifics of the organization. A significant part of the features of the economic activity of an enterprise
is determined by the type of its organizational structure. Results and conclusions. Therefore, the effectiveness
of the implementation of technological innovations depends on the suitability of the applied quality management
methods at enterprises of various organizational forms of management.
Rotorcraft Unmanned Aerial Vehicles (UAVs) often need to take off and land under complex working conditions. The rugged terrains may cause the UAV to tilt during takeoff and landing and even cause rollover and other accidents in severe cases. In this paper, a new four-legged landing gear of multirotor UAVs with a passive cushioning structure is designed, aiming at the landing stability requirement of rotorcraft UAVs in complex terrains. The mathematical model of the landing gear dynamics is established in MATLAB/Simulink, and the drop test simulation is carried out under different landing terrain conditions. By comparing the simulation results of the drop test multibody dynamic model in Simcenter3D dynamics software, the adaptive landing and cushioning capacity of the landing gear and the accuracy of the mathematical model are verified. Combined with the landing stability criterion and control strategy of adaptive landing gear adjustment, the landing stability of adaptive landing gear under different slope angles of landing surface and horizontal velocities is studied. The landing stability boundary under different combinations of these two parameters is found.
Methods based on received signal strength measurements (RSS measurements) are used to determine the unmanned aerial vehicle (UAV) location using a wireless sensor network. The UAV transmitter power is usually unknown. In real conditions, it often becomes necessary to consider existence of anomalous measurement results. The reasons for the violation of the measurement
process can be: the influence of interference, errors in the identification of signals during primary processing, failures of the equipment and similar. The optimum and quasi-optimal adaptive algorithms of UAV movement parameters filtration based on the RSS-measurement sensor networks in the presence of anomalous measurements at the unknown power of the transmitter are developed. These algorithms are obtained using Bayes’ theorems and the Markov property of a mixed process, including a vector of target movement parameters and a discrete component characterizing the type of measurement. Analysis of developed algorithm performance was carried out by Monte Carlo method on 2D plane. The quasi-optimal adaptive filtering algorithm detects the appearance of anomalous measurements with probabilities close to unity and allows one to eliminate their influence on the accuracy of UAV movement parameters estimation and also to estimate the UAV unknown transmitter power.
Technology, Motor vehicles. Aeronautics. Astronautics
On the basis of the study of air flight control, as well as the need to take into account the regional parameters of the airspace, the expediency and the need for mathematical modeling of the air navigation environment were identified. The article deals with the features of the model of air navigation environment, in which the base of the study adopted the basic information used to describe the plan for the execution of air flight. In the study, it was found that in navigation main feature is the geodesic of abstraction, however, such information was found, is not complete for the plan for air flight. The study emphasized the role of taking into account all the restrictions by which certain prohibitions on the use of specific volumes of airspace are imposed. Based on the results obtained, a graph of the geometric representation of the airspace with constraints was constructed. The results of the study allow us to conclude that the construction of a mathematical model of the air navigation environment allows us to achieve the following results: optimization of the distribution of the EAP loads by sectors, visualization of the air navigation situation in the region, the establishment of critical load directions, the collection of data on the load, the study of the factor effects on the regularity and safety of the aircraft movement. The mathematical model of the aeronautical situation was built with the help of a composition of hierarchical type. As a result of such construction of mathematical model its transformation with addition of new models is possible. Using the proposed mathematical model in the framework of discrete event systems can be used to simulate complex air navigation environment with a large number of aircraft. The use of the formalism presented in this study allows a clear distinction between the mechanism of information processing and the information itself in the process of modeling.
This paper investigated the fatigue damage coupling of composite laminate and metallic plate in multi-bolt joint. A progressive fatigue damage model for composite laminates and a modified Lemaitre damage model for metal material were developed. A phenomenological elastoplastic constitutive model was used to describe the in-plane shear nonlinearity of composite lamina. A formula for calculating the energy release rate of the low cycle fatigue was derived based on spherical tensor and shear tensor decomposition of the stress. The developed models were validated by the experimental results of a double-lap single-bolt metal-composite joint and were employed to simulate the fatigue damage of a double-lap, multi-bolt metal-composite joint. The result indicates that fatigue damage will harden the materials nearby the bolt region of the metallic plate for a multi-bolt joint structure when suffering to cyclic loads. This hardening behavior results to a transfer of bolt loads towards the harden region, which intensifies bearing damage and reduces tensile stress in the composite laminate, and improves the fatigue life of composite laminates fail in tensile mode.