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End-effector trajectory tracking of flexible multibody systems is a challenging task. In this paper feed-forward control designs based on quasi-static deformation compensation and exact model inversion for end-effector trajectory tracking are presented. They are combined with a simple feedback strategy and tested by simulation of a very flexible two arm manipulator. With both approaches good results for end-effector trajectory tracking are obtained. It is shown that a significant improvement of the inverse model approach is achieved by including the elastic rotation of the first arm in the system output description. This yields the far best accuracy of the tested approaches.

In recent years, topology optimization has been used for optimizing members of flexible multibody systems to enhance their performance. Here, an extension to existing topology optimization schemes for flexible multibody systems is presented in which a more accurate model of revolute joints and bearing domains is included. This extension is of special interest since a connection between flexible members in a multibody system using revolute joints is seen in many applications. Moreover, the modeling accuracy of the bearing area is shown to be influential on the shape of the optimized structure. In this work, the flexible bodies are incorporated in the multibody simulation using the floating frame of reference formulation, and their elastic deformation is approximated using global shape functions calculated in the model order reduction analysis. The modeling of revolute joints using Hertzian contact law is incorporated in this framework by introducing a corrector load in the bearing model. Furthermore, an application example of a flexible multibody system with revolute joints is optimized for minimum value of compliance, and a comparative study of the optimization result is performed with an equivalent system which is modeled with nonlinear finite elements.

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