Pre-shaping motion input for a rotating flexible link

The interest in the design of manipulators for space operations with a light structure has grown meaningfully in comparison with rigid manipulators, even if these flexible manipulators are unavoidably characterized by a not negligible structural flexibility. This paper deals with the first phase of a project financed by a grant from the Italian Space Agency (ASI) which is concerned with the setting up of an open loop control for a planar manipulator with flexible linkages. In this phase, the project is subdivided into two parts: on one hand, different command inputs have been proposed for point to point operations; on the other hand, dynamic simulations have been carried out by using a multibody model with flexible parts, in order to evaluate the residual vibrations due to the selected command input at the end of the motion. These command inputs will be applied to the actual manipulator, which is already available, in a future phase of the project. The command inputs, which are described here, are based on both the convolution of special impulse inputs suitably chosen on the basis of the system natural frequencies and the reduction of impulsive inertia forces by means of a suitable algorithm proposed here and derived from cam design. The simulations are carried out by commercial software for the study of multibody systems and custom programs for the command input implementation. The results obtained for the residual vibrations are compared to those obtained by conventional command inputs in the simulations on the same model.