Grasping Dynamic Modeling And Analysis For Manipulator With Joint Non- Linearity

With the rapid development of space industry, it is of great significance in the economy and safety that space manipulators are used to assist or replace the astronauts to complete some tasks in space. Space manipulator system is a typical rigid-flexible coupling system. Due to rigid-flexible coupling characteristics of manipulator and nonlinear characteristics of structure caused by the flexible joint, the in-orbit operation of space manipulators face many challenges. Basing on the detailed research in related fields'studies at domestic and abroad, this thesis gave a thorough analysis and research on flexible manipulator with nonlinear joint kinetics and grasping kinetics, including the followings:Firstly, take the planar rotating motion three link flexible manipulator for target, those factors such as transverse bending deformation, longitudinal tensile deformation and two-order coupling term of axial shrinkage which induced by lateral deformation were fully considered. Regarding the influence caused by nonlinear joints through the introduction of the rotor torsion-spring model, the dynamic model of flexible link and flexible joint manipulator was established by applying Lagrange method and hypothesis modal discretization method.Secondly, basing on the dynamic model of flexible link and flexible joint manipulator, the grasping dynamic of manipulator was analyzed. By introducing the concept of dynamic grasping domain to describe the whole grasping process, and based on Hertz theory to describe the process of contact-impact grasping characteristics, the influences of nonlinear joint were analyzed for the manipulator grasping process.Furthermore, the initiative joint damping control was used to inhibit the collision excitation in the grasping process. The deformation characteristics of flexible joint manipulator in uniform and accelerating grasp were analyzed.Finally, for the residual vibration when the manipulators finished grabbing the objective, the trajectory tracking and fixed-point vibration suppression of flexible manipulator with nonlinear joint was investigated by using the optimal control, basing on redundant degree of freedom manipulator dynamics and control characteristics.