FRIEND: an Extra-Vehicular Activity Retriever Telerobotic Project

The initial phase of the telerobot project FRIEND (Flying Robot with Intelligently Ended Nursing Dexterity) being developed at Politecnico di Milano, Dipartimento di Meccanica, is described. It has been designed for space activities, such as rescue and recovery of astronauts engaged in EVA in the area around the space station. The problem of grappling free-floating objects by the dual-arm telerobot is discussed. We examine the feasibility of arm operation only, without involving thruster activation. This strategy is believed to increase the safety of the operation and decrease totally thruster fuel consumption. A set of elemental moves (E-moves) is suggested which account for dynamic intercoupling of arm-link and main body rotation, as well as for kinematic and nonholonomic redundancy of the system. Each arm-motion subtask of the scenario is performed by a series of E-moves. Some subtasks can be executed by a predefined sequence of E-moves in autonomous mode, whereas others require on-line teleoperated motion control.