Contact Dynamics Of Space Net On Capturing Target

The modeling and simulation of the flexible space net collision dynamics are studied in this thesis.Space net system is a new research direction of space tether system. Space net can capture the targets with the features of non-cooperation, large quantity, irregular shape and spinning, so it has a very broad application prospects. Space net has strong nonlinear characteristics and numerical difficulty. Therefore, the flexible space net collision dynamics and flexible space net dynamics modeling are difficulties in the research of space net capture process.The flexible space net collision during the space capture is studied based on the flexible multi-body system dynamics theory and collision modeling method in this thesis. The main contents include:(1) The application background of space net and the domestic and foreign development status of the researches on the space tether system are introduced in this thesis. The flexible cable dynamics theory and the flexible multibody system collision dynamics theory which are associated with the flexible space net are also introduced.(2) A brief overall design of the space net system is done in this thesis. The space net and the grids all have a square shape. The space net is opened by ejecting the traction mass blocks which are mounted on its four vertices. And simulation results show that it is a convenient and efficient way to fold and eject the space net. The designed space net model provides a specific object for dynamics modeling and simulation. A set of performance evaluation parameters of space net system capture are proposed. And the instantaneous impact force, displacement and velocity change of the target and the spin angular velocity of the target are included in the parameters. The performance evaluation parameters provide the basis for the evaluation of the capture process.(3) The modeling of the flexible space net dynamics and the flexible space net collision dynamics are studied. Two kinds of cable element models are studied based on the lumped mass method and the absolute nodal coordinate formulation(ANCF), and the dynamics formulations of the two space net models are also deduced. The formulas of collision force and friction are deduced based on the nonlinear spring-damper model and Coulomb friction model. The collision detection process and the collision detection criterion are proposed.(4) The space net capture process simulation is researched. First, the comparation of two dynamic flexible cable models simulations is analysed, and the simulation results show that the flexible cable model based on the ANCF is superior to the cable model based on the lumped mass method, and it is more suitable for the modeling of flexible space net system with large deformation.(5) More in-depth studies of flexible space net are proceeded by designing different simulation conditions. The researches on the process of space net capture are mainly from the three aspects: the posture of target, the relative velocity and the mesh size of the net. The research results indicate that target posture, the relative velocity and the mesh size of the net all have a large affection on the space net capture, so the space net capture strategy should be designed according to the actual demand.