The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic modes.Particularly,a high-aspect-ratio flexible flying wing is pr...The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic modes.Particularly,a high-aspect-ratio flexible flying wing is prone to body freedomflutter(BFF),which is a result of coupling of the rigid body short-periodmodewith 1st wing bendingmode.Accurate prediction of the BFF characteristics is helpful to reflect the attitude changes of the vehicle intuitively and design the active flutter suppression control law.Instead of using the rigid body mode,this work simulates the rigid bodymotion of the model by using the six-degree-of-freedom(6DOF)equation.A dynamicmesh generation strategy particularly suitable for BFF simulation of free flying aircraft is developed.An accurate Computational Fluid Dynamics/Computational Structural Dynamics/six-degree-of-freedom equation(CFD/CSD/6DOF)-based BFF prediction method is proposed.Firstly,the time-domain CFD/CSD method is used to calculate the static equilibrium state of the model.Based on this state,the CFD/CSD/6DOF equation is solved in time domain to evaluate the structural response of themodel.Then combinedwith the variable stiffnessmethod,the critical flutter point of the model is obtained.This method is applied to the BFF calculation of a flyingwing model.The calculation results of the BFF characteristics of the model agree well with those fromthe modalmethod andNastran software.Finally,the method is used to analyze the influence factors of BFF.The analysis results show that the flutter speed can be improved by either releasing plunge constraint or moving the center ofmass forward or increasing the pitch inertia.展开更多
This paper investigates the six degree-of-freedom(6DOF)relative kinodynamic motion planning problem for spacecraft close approach operations,wherein a controlled chaser spacecraft is required to approach a noncooperat...This paper investigates the six degree-of-freedom(6DOF)relative kinodynamic motion planning problem for spacecraft close approach operations,wherein a controlled chaser spacecraft is required to approach a noncooperative space target at a close range under both dynamic constraints and motion constraints.An enhanced version of the bidirectional rapidlyexploring random tree^(*)(BiRRT^(*))algorithm based on flight zoning(FZ-BiRRT^(*))is proposed to generate safe,feasible,and nearoptimal relative motion trajectories.In the proposed algorithm,the space surrounding the space target is zoned in a spherical coordinate system based on the collision probability so that specific designs can be made for different phases of the approaching.Subsequently,based on the flight zone,dynamic constraints,and experiential knowledge,a series of modifications are made to the classic BiRRT^(*)algorithm,and a postprocessing step is designed to accelerate convergence and promote search efficiency.Furthermore,a general regression neural network is introduced to fit a smooth and applicable final motion trajectory.Finally,the feasibility of the generated motion trajectory and the superiority of the proposed algorithm is demonstrated by means of numerical simulations.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.11872212)and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic modes.Particularly,a high-aspect-ratio flexible flying wing is prone to body freedomflutter(BFF),which is a result of coupling of the rigid body short-periodmodewith 1st wing bendingmode.Accurate prediction of the BFF characteristics is helpful to reflect the attitude changes of the vehicle intuitively and design the active flutter suppression control law.Instead of using the rigid body mode,this work simulates the rigid bodymotion of the model by using the six-degree-of-freedom(6DOF)equation.A dynamicmesh generation strategy particularly suitable for BFF simulation of free flying aircraft is developed.An accurate Computational Fluid Dynamics/Computational Structural Dynamics/six-degree-of-freedom equation(CFD/CSD/6DOF)-based BFF prediction method is proposed.Firstly,the time-domain CFD/CSD method is used to calculate the static equilibrium state of the model.Based on this state,the CFD/CSD/6DOF equation is solved in time domain to evaluate the structural response of themodel.Then combinedwith the variable stiffnessmethod,the critical flutter point of the model is obtained.This method is applied to the BFF calculation of a flyingwing model.The calculation results of the BFF characteristics of the model agree well with those fromthe modalmethod andNastran software.Finally,the method is used to analyze the influence factors of BFF.The analysis results show that the flutter speed can be improved by either releasing plunge constraint or moving the center ofmass forward or increasing the pitch inertia.
基金supported by the Science Center Program of National Natural Science Foundation of China(62188101)the National Key Research and Development Program of China(2024YFF0504702)the SiYuan Collaborative Innovation Alliance of Artificial Intelligence Science(HTKJ2023SY502003).
文摘This paper investigates the six degree-of-freedom(6DOF)relative kinodynamic motion planning problem for spacecraft close approach operations,wherein a controlled chaser spacecraft is required to approach a noncooperative space target at a close range under both dynamic constraints and motion constraints.An enhanced version of the bidirectional rapidlyexploring random tree^(*)(BiRRT^(*))algorithm based on flight zoning(FZ-BiRRT^(*))is proposed to generate safe,feasible,and nearoptimal relative motion trajectories.In the proposed algorithm,the space surrounding the space target is zoned in a spherical coordinate system based on the collision probability so that specific designs can be made for different phases of the approaching.Subsequently,based on the flight zone,dynamic constraints,and experiential knowledge,a series of modifications are made to the classic BiRRT^(*)algorithm,and a postprocessing step is designed to accelerate convergence and promote search efficiency.Furthermore,a general regression neural network is introduced to fit a smooth and applicable final motion trajectory.Finally,the feasibility of the generated motion trajectory and the superiority of the proposed algorithm is demonstrated by means of numerical simulations.
