| The activities of space exploration have been greatly development with the rapid development of science and technology. The space station as one of the most advanced of large spacecraft, which plays an irreplaceable role in deep space exploration, space life science, new technology research and other fields. The construction, maintenance of space station and astronaut extravehicular activities all needs to be done by the large space manipulator. With the need of faster response and wider scope of space manipulator during space operation, the application of flexible manipulator is more and more widely, not only reduce the launch costs, at the same time greatly improve the efficiency of space operations. The process of space operation will provoke obvious low frequency vibration, because flexible space manipulator is qualitative light, low stiffness and other characteristics. Such vibration not only cause end actuators can’t accurate positioning, but cause the vibration of the combined spacecraft in microgravity,low damping environment. Dynamics analysis and vibration suppression of large flexible space manipulator has been the focus of research scholars both here and abroad. This paper regards the flexible space manipulator that mounted on the core module of space station as the research object, mainly on the flexible space manipulator kinematics and the dynamics modeling of space manipulator inversion system, dynamics characteristics analysis and active vibration suppression method research.Flexible space manipulator belongs to the typical space unfolding agency, it needs to fold to the specified location before the space operation. Due to the kinematics coupling of the free floating space manipulator, the motion of the flexible space manipulator will change the attitude of the base. In this paper, the kinematics of free floating space manipulator was analyzed, and applied genetic algorithm on the manipulator joint angle trajectory planning with zero disturbance of the base eular attitude. This paper presented the numerical simulation to validate the feasibility of the method.Flexible space manipulator inversion system includes two flexible arms and connected with the big quality, big moment of inertia of rigid body, which belonging to the chain four segments multibody dynamics system with characters of highly nonlinear, strong coupling complex. To establish accurate dynamic model is the basis of dynamic analysis and vibration suppression. The paper applied finite element method(FEM) to character the elastic deformation of flexible manipulator, Newton-Euler method to establish the rotation equation of system, Lagrange method to set up the vibration equation, and applied the constraint modal method to solve the dynamic equation. This paper analyzed the vibration characteristics of the chain four segments multibody dynamics system, developed the dynamics calculation program based on the MATLAB programming language, and established the semi physical simulation model with ADAMS and ANSYS software respectively. The results computed by the two different ways verify the validity of the theoretical model.According to the calculation for the coupled system of vibration frequency and damping, applied component synthesis vibration suppressing method(CSVS) to design joint driving moment. By this way, the joint realized the specified angular displacement and inhibit off low-order vibration modal. Because the CSVS is sensitive to parameter variations caused by time-varying system structure, this paper combined PD linear decoupling feedback with CSVS as new closed-loop complex control method. According to the vibration frequency and damping ratio of the closed-loop system, this paper applied the complex control method to design the joint angle input, realized the trajectory tracking of the joint angle displacement and lowered the elastic deformation of flexible manipulator and the angle disturbance of the core module. The feasibility and effectiveness of the method is validated by numerical simulation. |
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