Abstract:A recursive radial basis function (RRBF) neural network is applied to construct unsteady aerodynamic model, which leads to a dynamic nonlinear reduced order model (ROM). The widths of basis function in hidden layer is one of important parameters to this aerodynamic model.To investigate the effects of widths for RRBF neural network, mathematical analysis and simulations are executed at first, which shows the relationship between widths and framework of the model during training process. Then cases of NACA 0012 aerofoil with pitching maneuvers are simulated, to test the model under different training maneuvers, previous time steps and flow states. Results show that the widths of basis function have much impact on the stability and generalization ability of this type of aerodynamic model. The best width varies with different training and testing maneuvers. With more samples, higher predicting accuracy of aerodynamic model is guaranteed with widths between 55~75. Predicting results of random pitching maneuver verify the conclusion of best widths scale in the paper.

Abstract:To meet with airworthiness requirement of transport category airplane landing gear design, Flow to calculate ground handling load was introduced aiming at CCAR25 regulations, Method named ‘Virtual Contact Point’ rotation was raised to gain landing gear basic size data and airplane attitude based on tire and absorber strut deflection data. Landing gear ground handling load results were gained by the flow, These results included airplane attitude under certain ground handling load case, ground load under ground coordinate system and aircraft coordinate system, and landing gear basic size data. The flow and the ‘Virtual Contact Point’ rotation method was accurate and reliable, and meeting with CCAR25 regulations requirement well by ground turning load case calculation and discussion of the case result.

Abstract:Plasma actuators can be used in flow control applications due to the accelerated airflow transfer from plasma to fluid. Due to geometry limitation, however, only small trust can be obtained by DBD plasma actuators, which limits its application in large-scale flow problems. Usually, several surface DBDs are combined in series to obtain a single multistage actuation surface. However, the reverse discharge between successive discharges limits the effectiveness of such multi-DBD actuators. In this paper, a new multi-bipolar DBD plasma actuator is proposed for large-scale flow control applications. An innovative method for constructing multiple plasma actuators of bipolar electrodes is introduced to enhance the thrust. Multi-bipolar electrodes are adopted with the electrode of former covered electrode and later exposed electrode connected together. To validate the proposed method, particle image velocimetry (PIV) experiments are performed. The results show that the multi-bipolar actuator electrode plate is not affected by reverse discharge. The adsorption of the atmosphere and the control effect is obvious.

Abstract:The accurate prediction of boundary layer transition of aircraft is the key of getting laminar airfoil with high performance. This paper selects the Gamma-Theta transition model coupled with the SST k-w turbulence model based on the characteristics of numerical simulation of boundary layer and CFD technology, to achieve the accurate prediction of airfoil boundary layer transition of different types. At the meantime, enhancing the grid equality can increase the computing accuracy of the aerodynamics characteristics of airfoil to some extent, and obtain more precise result of transition location.

Abstract:It is well-known that the fatigue lives of metal material have a considerable amount of scatter and they are commonly suggested to be considered in engineering design. A rational computational method is proposed for identifying the probability distribution of fatigue life in this paper, in order to reduce the introduction of subjective uncertainties and obtain rational probability distribution. Firstly the sample statistics are used to estimate the first four statistical moments of fatigue life. Then, based on all those statistical moment constraints, the maximum entropy principle is employed to identify a rational probability distribution for fatigue life of interest. An accurate algorithm based on optimization theory is also presented to find the Lagrange multipliers in maximum entropy distribution, which can avoid the numerical singularity when solving a system of equations. The rationality and effectiveness of the proposed method are demonstrated by the experimental data of 2024-T351 aluminum alloy specimens available in the literature.

Abstract:To study the influence of different geometric parameters including the radius of shell, shell thickness and the crack length on the bulging factor, this paper calculates the bulging factors of unstiffened pressurized cylindrical shells with longitudinal crack by geometric nonlinear finite element analysis in ABAQUS, the numerical results of bulging factor are compared with existed empirical solutions, the effect of biaxial load on the bulging factors is also discussed. The results indicate that the bulging factor is influenced strongly by most of the geometric parameters; limitations on the use of empirical solutions do exist; Increasing biaxial load ratios from 0.5 to 1.0 reduces the bulging effect by 20%. Conversely, decreasing biaxial load ratios from 0.5 to 0 increases the bulging effect by 28%.

Abstract:The water bags are the decelerator of rocket sled high-speed test, which added mass is large, and the operating speed is fast, thus having to bear great load when using the impact of water to decelerate. In order to ensure the safety of the water bags structure and achieve the expected deceleration effect, numerical simulation analysis must firstly be done on the water bags movement condition. Using the fluid-solid coupling technology of Abaqus and the method of CEL, the movement condition of the water bags is analyzed. Using the resistance curve obtained from the simulation analysis, and based on fluid resistance theoretical calculation formula, the calculation formula of the water bags resistance is acquired. The water bags resistance under different speed and initial water level can be calculated from this calculation formula, thus obtaining the deceleration performance of the water bags.

Abstract:To solve the problem of power compensator for lift-fan UAV, this paper focuses on the design and analysis of the power compensator system during the landing process of lift-fan UAV. Firstly, the longitudinal state equation of lift-fan UAV was established and simplified. And then, the basic control structure of power compensator was built. Finally, aiming at the characteristic of lift-fan UAV, the power compensator system integrating various compensators was established, and this system was simulated and analyzed. The result indicates that the simulation response time in the power compensator system at the constant speedis shorter than the other.However, the damping which can cause oscillation is deficiency. In order to alleviate the oscillation, subsequently, the longitudinal overloading is analyzed according to the specific characteristics of lift-fan UAV, and the effect of power compensation with spoiler is also researched. The results show that modes of aircraft are goodand effectively increase the tracking precision of the attitude angle of flight path angle.

Abstract:For reduced-order accuracy and control system design of model reduction in active control, the folding wing is taken as an example. The structural dynamic model is established based on the modal synthesis method. Two different reduced order models are obtained by virtue of modal cost analysis and balanced truncation. The comparisons and analyses of two different reduction models rely on degree of controllability and degree of observability. Finally, the optimal control law is applied to the reduction models to restrain the vertical displacement of the wing tip. The results indicate that the degree of controllability of balanced truncation reduction model is higher while the degree of observability of modal cost analysis reduction model is higher. The low order model of structural dynamic model can be achieved using two different reduction methods quickly and precisely. It is effective to design the active control system for the low order model.

Abstract:Nose gear buffering and steering rectification have significant influence on landing gear design. Rigid-flexible coupling dynamic models for both articulated and post nose landing gears have been constructed respectively based on the same aircraft by in this paper. Contrastive analysis and dynamic simulations have been performed by applying previous models, traits of these two types of nose gear on landing buffering and steering performance have been deduced from the analysis. During the same landing case, tangential force is bigger for post nose gear, yet pitching angular velocity after touching ground and nose sinkage remain similar. Articulated nose gear is more likely to sideslip under smaller operating torque, steer angle and lateral acceleration compared with post nose gear. The results of this paper offer a meaningful share of reference materials for nose gear design and selections.

Abstract:The performance of landing gear extension/retraction system is of direct influence of safety and comfortable of aircraft. A landing gear extension/retraction system of certain domestic plane is taken as study object. To test the performance of the retraction/extension mechanism of a landing gear of a certain aircraft, the mathematic model of the retraction/extension mechanism is presented, and it's performance simulation is based on the 3D model of the landing gear and the 1D model of the hydraulic control system by LMS Imagine.Lab AMESim and LMS Virtual.Lab Rev的Motion software. The result shows that this retraction/extension mechanism with theoretical values can complete its extending-and-retracting task during a limited time. The simulation results which consider aerodynamic load are in good agreement with actual trend and can be as a design reference. Besides, with the help of the co-simulation model, the influence of the parameters of the uplock damping on the extension/retraction performance is studied, and it is suggested that the parameters of the uplock damping are prior selection during the extension/retraction optimization progress can be as reference of the optimization design.

Abstract:To obtain the effect of water wash on improving civil aero-engine performance, realize the transition from a hard time water wash to on condition water wash, and provide support for assessing the effectiveness of energy saving for an airline, an effect evaluation method of aero-engine water wash is proposed. The method chooses the extending time on wing and the saving fuel quantity as main evaluation indicators of evaluating the effect of aero-engine water wash, and calculation methods of evaluation indicators are put forward. The effect evaluation model based on cost of aero-engine water wash is established, and water wash effect can be evaluated based on the model. The proposed method is validated by the actual data from an aero-engine after water wash. Results show that the proposed method can achieve a quantitative evaluation of the effect of aero-engine water wash. Finally, an aero-engine water wash management system is developed based on the proposed method. This study can provide support for the implementation of on condition water wash, and also provide support for assessing the effectiveness of energy saving for an airline.

Abstract:Override rod linkage form is adopted by the cockpit control units of a certain type of fly-by-wire civil aircraft, and it brings some profits on the weight and maintainability while the problems it resulted in are the failure mode becomes diverse and complicated. For the problem, this paper does a research on the working principle and physical characteristics of the cockpit control units, through modeling and simulation on its normal mode and failure mode, and finally gives an analysis and evaluation for the column force quality of each failure mode. The simulation results reveal the column force quality of each failure mode is acceptable.

Abstract:The particle swarm algorithm is used on the optimization of aviation projects resources to solve the low utilization and the concentration requirement of resources. A mapping relation between the projects start time and the particle attributes has been built by establishing the solution space of resource equalization optimization. The start time of non-critical node is solved by using MES of resource requirement as evaluation function and task logical relation as constraints. Then a detailed optimization scheme is proposed and the resource requirement peak is reduced effectively. The algorithm is verified by the typical wing assembly process. It shows that this method can prevent resource pooling problem effectively.

Abstract:A fast online nonlinear model predictive control (NMPC) approach was applied to trajectory tracking of miniature coaxial unmanned helicopter(MCUH). The nonlinear model of MCUH was simplified. And then, utilizing the differential flatness of MCUH, a linear time varying (LTV) model was employed to approximate the nonlinear dynamic behavior of MCUH, and further on applied in the conversion from classical NMPC schemes to LTV-MPC schemes for output trajectory tracking, resulting in reduction of the complexity of the problem solving. Afterwards, the terminal region and the end penalty were designed to ensure the exponentially asymptotically stable of the trajectory tracking error system. The numerical simulation verified the proposed NMPC control scheme to the time-varying trajectory tracking of MCUH with constraints.

Abstract:The property of technical、mechanical and environmental of three kinds integral fuel tank sealant used on jet were introduced, and combined the demand of the air tightness of the jet, the application of the sealant were also introduced.

Abstract:With the purpose of guiding domestic ETOPS type design, civil aircraft ETOPS type design was studied in this paper. The ETOPS definition and development process was briefly introduced. Airworthiness requirement and approve method for civil aircraft ETOPS type design was sorted. Based on researches on airworthiness material, an ETOPS type design idea was proposed. In engineering practice, it was turned out that the design flow proposed in this paper can guide the ETOPS type design for domestic civil aircraft.

Abstract:Abstract: As the fatigue life of airborne evaporation circulatory system structure is susceptible to the influence of external and internal environment, it does not satisfy the design requirements. Based on stochastic finite element method and considering the variability of design variables and other random variables, a mathematic model of the robustness optimization of fatigue life is established. As the robustness optimization of fatigue life of the airborne evaporation circulatory system structure robust optimization is studied, the robustness of fatigue life problem is transformed into the double objective problems of mean and standard deviation of fatigue life, which effectively reduces the sensitivity of the design variables for fatigue life and improves the robustness of fatigue life by setting the power factor of mean and standard deviation of fatigue life.

Abstract:Aircraft electromagnetic launch can increase the take-off speed of the aircraft, increasing the aircraft payload, saving energy consumption and reduced the maximum thrust requirements. Use the "Underground LIM traction on ground vehicle transportation method" for the aircraft electromagnetic launch traction, the “The ring kinetic energy storage with vacuum magnetic levitation rotating shaft support structure " as high-power pulsed power. By engineering the overall design to solve the security and stability of energy supply system, multi backup, high redundancy, high reliability, high power pulse power energy storage system to achieve safe, continuous, reliable linear motor Aircraft ground electromagnetic launch project system.