Research On Analysis Platform For Dynamic Response Of Flexible Body Undergoing Large Overall Motion

In modern aerospace, flexible spacecraft is widely used. The large overall motionof the flexible spacecraft belongs to the research areas of flexible multibody systemdynamics which is a special issue of multibody system dynamics. Due to the couplingof deform and motion, the response of flexible multibody systems is morecomplicated. So a reasonable rigid-flexible coupling dynamics model are required. Inthis dissertation, the coupling mechanism of deform and motion of flexible bodyundergoing large overall motion is researched, and the study object is flexible solidstructure and flexible beam. The analysis platform to solve this type of issue is alsobuilt.The traditional hybrid-coordinate method is widely used in flexible multibodysystem dynamics. The deform of flexible body is described in the coordinate movingwith flexible body. This method is a coupling modeling method of zero orderapproximation(MZOA), so it can only solve a sort of problem in which the deform offlexible body is small. However, as the development of technology, flexible multibodysystems are much more complicated. In some cases, the traditional hybrid-coordinatemethod will give the wrong result. In the year of1987, Kane found that MZOA willgive a divergent result when the angular velocity of a cantilever exceeds a criticalvalue. From then on, the flaw of MZOA was realized and more and more researchersbegan to find a more accurate model. Obviously, reliability is the primary standard ofa new model to apply to the engineering. So this dissertation is to build a morereliable rigid flexible coupling dynamics model.The method of this dissertation is based on the traditional hybrid-coordinatemethod. Three reference frames are used: global frame to build dynamics equations,floating frame moving with flexible body and element transformation frame. Thefloating frame detach the motion and deform of flexible body and the elementtransformation frame make the description of deform more easier. With the help ofKane Equations, the dynamics equations are built in global frame. Different with the traditional hybrid-coordinate method, the method in this dissertation adopt nonlinearstrain-displacement theory to express the deform. So it can solve the Flexiblemultibody system dynamics issues even when the system have large deformationbecause of the keep of higher order rigid flexible coupling terms. The study object ofthis dissertation is flexible solid structures and flexible beams which are discretizedby eight-node hexahedral isoparametric element and Euler beam element respectively.Using the principle of virtual work of nonlinear finite element, the equilibriumequations of flexible body are built. The dynamics equations are solved with centraldifference method to get the response of rigid flexible coupling systems.