Analysis and Test of a Space Manipulator Modeling Approach

Robotic operations in space require very light and hence flexible manipulators. Their guidance and control should be based on dynamic characteristics of the structure, requiring a very accurate modeling of the flexibility effects during the motion of the manipulator. The equation of motion of the overall mechanical system under gravity, gravity gradient, thermal and dissipative forces must be formulated in order to provide a suitable computation of the control actions. Lagrangian approach has been used in the past, but unfortunately provides equations which are not easily ‘’readable’’ from that point of view. Newtonian approach coupled with a multibody formulation leads to the description of a complex systems in a more feasible way to design structural components and actuators, allowing to evaluate explicitly the forces and the stresses acting on the structure. This formulation can be numerically efficient – for both simulation and real-time guidance - enabling to identify the order of magnitude of different contributions (orbital, attitude, flexibility). The paper presents a mathematical insight on this approach to model multibody space manipulators, taking into account the space environmental and control forces expected while grasping an orbiting target. A manipulator setup purposely developed in the labs of University of Rome La Sapienza to gain experience on the technological problems is discussed, providing indications for the hardware selection. Key Word