<title>Modeling of a nonlinear space robotic system for precision and control</title>

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Many structures in space exhibit nonlinear behavior. These nonlinearities arise due to coupling of rigid body and structural flexibility effects. Large angle attitude maneuvers such as slewing, tracking, or precision pointing (under certain operating conditions) involve nonlinear dynamics associated with rigid body kinematics. The resulting dynamical equations of motion of such systems are coupled and highly nonlinear. However, the current state of the art in design of control laws for these systems is based on linear control theory. Nonlinear systems, therefore, need to be linearized before attitude control laws can be applied. Recent research in control theory has led to nonlinear control laws capable of completely decoupling the flexible and rigid body modes. The goal of our research effort is to assess the effectiveness of these linearizing and decoupling control laws. The results of this effort will serve to provide techniques for modeling of complex flexible nonlinear space system such as the space robotic systems. In general, the paper addresses nonlinear inversion based on feedback linearization and robust stabilization of the unobserved dynamics of the linearized and decoupled system. Simulation results with some interesting insights are presented for space systems subject to rapid, large angle slewing and precision pointing. The contribution of this research lies in the development of a unified approach for modeling of a nonlinear multibody flexible system based on nonlinear inversion. The approach is valid for modeling of space robotics systems which are nonlinear multilink flexible systems.