Aerospace Systems最新文献

In this paper, a novel on–off linear quadratic regulator (LQR) control for satellite rendezvous as an example of linear systems with on–off inputs has been proposed for the first time. It simultaneously benefits from unique potentials of LQR control method and the extensive applications of systems with on–off inputs in various areas. The on–off LQR control approach has been applied on the system of orbital rendezvous and docking of satellites equipped with thrusters which are appropriate samples of systems with on–off inputs. Because of the energy consumption significance in many practical applications, the proposed approach is designed to consume less energy as well. Simulation results show the energy consumption of the presented method has been reduced about 36% compared to the continuous LQR approach.

Fiber-reinforced composite laminates are widely used in aerospace and other fields. Delamination damage is the main damage form of laminates, which has always been one of the focus problems of composite mechanics. Virtual crack closure technique (VCCT) and cohesive zone modeling (CZM) are two well-known numerical methods frequently used for crack propagation modeling. In this study, to better understand the advantages and limitations of these two methods, as well as the process of practical application, the evaluations on them are conducted. A double cantilever beam (DCB) specimen, an end notched flexure (ENF) specimen, and a mixed-mode bending (MMB) specimen as benchmark examples are modeled in ABAQUS. The mode I, mode II, and mixed-mode (I + II) delamination initiation and propagation behaviors of unidirectional specimens are simulated using two above methods. Finite element (FE) results are compared with experimental results available in the literature to verify the validity of the FE models. Finally, the accuracy, convergence speed, run-time, mesh dependency, and influence of modeling parameters of each method are discussed based on the simulation of DCB test.

Predicting the trajectory of the airship during its ascent before it is released has significance in avoiding possible accidents. To achieve this, a new coupled thermodynamics and dynamics model is developed. A rigid body model with 6 degrees of freedom is adopted. Time-varying aerodynamic forces and mass distribution parameters are also included in this model. The thermodynamic model considers the heat transfer process of radiation and convection among the film of airship, helium, internal air, and atmosphere. The simulation results show that more accurate results can be obtained using the rigid body model with six degrees of freedom compared with the three degrees of freedom model. The existence of the sunlight will also affect the movement of the airship, which will cause the temperature of the buoyant gas to increase and the airship to move faster. Some factors which will affect thermal behavior of helium are also investigated. Results show that the larger the initial helium volume is, the more serious the supercooling phenomenon of helium will happen. The greater the solar radiation absorptivity of the film is, the lower the supercooling temperature will be, but it will cause helium more hotter during floating stage. The overpressure of the airbag has no significant effect on the motion of the airship.

Continuous growth of aircraft speed and altitude has a decisive influence on changes in their aerodynamic layout and structural-power diagrams, which leads to significant changes in the shape and thickness of wing profiles. The paper proposes a probabilistic-time approach to the solution of the actual problem of assessing the strength of a caisson wing structure. At the same time, a quasi-static methodology is used, according to which the probability of failure is considered at the most critical points, and the calculation is carried out at a fixed point in time, at which the loading of the wing structure is the most dangerous. The loads and load capacity of the wing in this approach are random values, which necessitates the use of statistical modeling in the calculations. On the basis of the authors' earlier researches, an engineering method of the strength calculation of the aircraft caisson wing has been developed, involving analytical and statistical modeling to estimate the influence of the safety factor on the probability of its non-failure operation. This methodology can be widely used in the design of aircraft as statistical material on the wing loads and its strength characteristics is accumulated. Numerical experiments based on Monte Carlo method for calculating the probability of no-failure operation of the caisson wing have been conducted. The dependences of the probability of no-failure operation on the safety factor for the most interesting, from the viewpoint of engineering practice, the non-failure range from 0.99 to 0.999 were obtained.

This study aimed to develop an approach for the understanding of the relationship between the contact interaction properties of lugs and their strength and mass to design efficient and lightweight lugs for aerospace components. Lugs are crucial components of many aerospace mechanisms, and their properties are closely linked to their contact interactions with bushings. The approach taken in this study involved modeling the adhesive layer between the lug and bushing and optimizing the dimensions of the polymer lug and metal bushing to minimize the lug’s mass while maintaining adequate strength. Finite element analysis (FEA) and cohesive zone modeling (CZM) were used to simulate the effects of primary properties of contact interaction between lug body and bushing on the strength and mass of the lug, and both gradient-free and gradient-based optimization algorithms were employed to minimize the lug’s mass while maintaining its strength. The results showed that increasing shear and tensile contact strengths reduced the resulting mass, with tangential stress having the greatest effect. Moreover, increasing contact strength reduced the required dimensions of the lug and bushing, indicating the possibility of reducing the mass of the bushing–lug assembly using rougher bushings or ribbing.

Non-uniform inlet conditions have become increasingly important in recent years for simulating the aerodynamic performance of turbofan engine with real flight situations. This paper focuses on a particular fan and booster structure and employs frozen rotor interface method for 3D full-channel CFD simulation. Inlet distortion and rain ingestion are used as two representative non-uniform inlet conditions discussed in this work. It is found that the circumferential total pressure distortion develops along the flow direction, and leads to total temperature distortion. Additionally, the regulation of rain movement in fan and booster structures is investigated, and some factors about water inlet ratio impacting the performance of core engine and wet compression mechanism affecting the bypass performance are discussed.

Design, production, testing, and operation of reusable launch vehicles are promising areas of development and theoretical research in the field of systems for the maintenance, repair, restoration, and operation of aircraft, including reusable transport rocket and space systems, are relevant. The article is aimed at harmonizing the design solutions of technical systems related to measures for their maintenance during storage. The purpose of the article is to develop methods and algorithms that allow matching performance characteristics and design solutions. The scientific problem is solved by compiling and analyzing the state graph of maintenance models using the Kolmogorov system of differential equations. As a result, the models obtained make it possible to predict the performance of maintenance of complex technical systems during storage and explore the possibility of reducing downtime for maintenance without a significant decrease in the quality of maintenance, namely: to evaluate the optimal maintenance period, to agree on the reserve ratio and maintenance period (costs maintenance depending on the ratio of the reserve), choose the optimal strategy for scheduled maintenance, taking into account the continuous monitoring of the technical condition of the aircraft, evaluate the intensity of failure recovery during continuous and periodic monitoring, and justify the most appropriate ways to improve the quality of service, provided that downtime for maintenance is limited and predict the probability of detecting faults during maintenance.

The problem of finding a (H_{infty } -) observer of the state vector of a linear continuous non-stationary dynamic system with finite time of functioning is considered. It is assumed that a mathematical model of a closed-loop linear continuous deterministic dynamic system with an optimal linear regulator, found as a result of minimization of the quadratic quality criterion, is known. We find a solution to the problem of state vector coordinates estimation in the presence of limited external influences and disturbances in a linear model of the measuring system. As an example, the equations of motion of an L_1011-type airplane are used.

This research is mainly devoted to numerical trade studies of a co-rotating array of mini-air-jet vortex generators (Mi-AJVGs) placed on a supercritical P-18-415 airfoil-based wing model. The numerical simulation is carried out at an angle of attack α = 4° and Mach number M_∞ = 0.75. Three-dimensional compressible Reynolds Averaged Navier–Stokes (RANS) equations coupled with the k-ϵ realizable turbulence model are employed with an assumption of fully turbulent boundary layer. The result is the best design case out of the investigated ones in terms of the skin friction coefficient and the lift-to-drag ratio. When the Mi-AJVGs are activated, streamwise vortices acting on the separation region increase downstream skin friction and the lift-to-drag ratio. The effect of the jet to ambient temperature ratios (T_J/T_∞) on aerodynamic performance is considered.

In order to improve the performance of a navigation systems, scintillation studies and Ionospheric Total electron content (TEC) are important. The amplitude scintillation index (S₄), S₄ corrections and Rate of change of TEC index (ROTI) parameters are analysed for different seasons. For the analysis Visakhapatnam station (Lat: 17.78, Long: 83.22) and Lucknow (Lat: 26.76, Long: 80.88) station, GAGAN receiver data for the year 2016 is considered based on four quiet days and four disturbed days and consider the highest Kp index values for Visakhapatnam station and Lucknow station. This work shows the variation of S₄ index and ROTI parameter variation during different seasons for both the stations. The correlation coefficient (CC) of S₄ index and ROTI are presented. The results show that the CC are high for disturbed days compared to the quiet days for both the considered stations. For Lucknow station, it is observed that CC values are high compared to the Visakhapatnam station.