Research On Dynamic Modeling Of Flexible Space Manipulator

With the steady advancement of China’s space industry,space manipulators have been gradually used in China’s space missions.The first step to perform dynamic control and motion planning is dynamic modeling of the space manipulator.The dynamic characteristics of the space manipulators are very different from those of the ground industrial manipulators.On the one hand,the space manipulator has a large working space and high end load,and its dynamics shows obvious rigid-flexible coupling characteristics;on the other hand,there is a strong motion coupling effect between the space manipulator and the carrier spacecraft.Aiming at the dynamic characteristics of the space manipulator’s floating base and rigid-flexible coupling,the dynamic modeling of the space manipulator system is studied in this paper.Firstly,the fixed-base full-rotation rigid manipulator is used as the research object,and the topology structure of the manipulator is described by using the directed Span tree.Since the characteristics of the elastic deformation of the arms can be described intuitively by the floating coordinate system,the floating coordinate system method is employed to establish the recursive forward kinematic model of the fixed-base manipulator.On this basis,an explicit dynamic model of the fixed-base rigid manipulator was established by using Lagrange’s second type equation,and the correctness of the model was verified by the principle of energy conservation.Secondly,based on the dynamic model of the fixed-base rigid manipulator,the system is discretized by using the finite difference method,and the explicit dynamic model of the fixed-base flexible manipulator was established.The corresponding dynamic simulation software is developed to verify the correctness of the dynamic model of the manipulator,and the dynamic characteristics of the flexible manipulator are studied.The simulation results show that when the flexible member is discretized into 11 segments,the simulation results can meet the accuracy requirements;within a certain range,the elastic modulus of the root member does not significantly affect the elastic deformation of the end of the robot arm.In order to effectively suppress the elastic deformation displacement of the end of the manipulator,the elastic modulus of the rod at the end of the manipulator should be appropriately increased;within a certain range,the cross-section height of the root rod has no significant effect on the elastic deformation of the end of the manipulator.To suppress the elastic deformation displacement of the end of the manipulator,the section height of the rod at the end of the manipulator should be appropriately increased.Finally,based on the explicit dynamic model of the fixed base flexible manipulator,the explicit dynamic model of the free-floating base flexible manipulator was established,and the corresponding software was developed to verify the correctness of the model.