Research On Dynamic Modeling And Motion Control Of Spececraft Flexible Appendages Based On Absolute Nodal Coordinate Formulation

With the rapid development of space industry,the missions of spacecraft have become more and more complex and diverse in recent years,and varieties of appendages attaching to spacecraft are also needed to accomplish different complex and diverse space missions.The development tendency of light weight and flexibility of spacecraft appendages makes it not simply to be considered as a rigid multi-body system while considering its related dynamics problems are concerned.Therefore,it is important to research on the dynamics modeling and motion control of these flexible appendages.In this paper,a series of problems related to dynamics modeling,dynamics analysis and motion control of typical spacecraft flexible appendages including truss structure and flexible manipulator are investigated as follows:A brief introduction to the theory of continuum mechanics and the absolute nodal coordinate formulation unit derived from it.the dynamics of flexible appendages are modeled by one-dimensional two-node beam units and the dynamics equations of flexible appendages modeled by one-dimensional twonode beam units based on the principle of virtual work were carried out.Taking the dynamic equations of a flexible attachment established by onedimensional two-node beam units as an example,two solution methods are briefly introduced,and the correctness of the method for solving the dynamic equations is verified by comparing the solution results of these methods with commercial software’s.Based on multi-body dynamics,a method for solving the dynamics equations applicable to some specific objects is proposed,and the correctness of the solution method is verified by comparing the energy in the process of solving the method.Typical planar truss structure in the flexible appendages of spacecraft was carried out for the dynamics analysis,and the simulation results with different unit numbers were compared.The result shows that while the spacecraft appendages flexibility was considered,with obvious hysteresis,planar truss structure remains vibrating during the motion and continues to vibrate at the end of the motion.This simulation result shows that the flexibility of the spacecraft appendages will bring a large impact on its motion.A strategy for motion control of a flexible appendages is proposed with an example of end trajectory tracking control of a flexible manipulator.The driving torque of the rigid body is considered as the feedforward input,and the error generated during the motion is considered as the feedback to control the motion of the flexible appendages.Two typical end trajectories of the flexible manipulator are simulated and analyzed,showing the effectiveness of this control strategy.