Managing Contact Dynamics for Orbital Robotic Servicing Missions

Abstract

Managing the contact dynamics between a robotic servicing vehicle and a client spacecraft is one of the most fundamental capabilities required to enable robotic servicing missions. Managing contact dynamics is especially challenging when designing servicing missions for existing space assets, since soft capture devices are not often present on current generation spacecraft. This paper details the contact dynamics management strategies employed on the Naval Research Laboratory’s FREND project, a DARPA-sponsored technology development program aimed at designing and building a robotic payload capable of grappling and repositioning existing space assets. The technological centerpiece of FREND is a space-rated 7DOF robotic manipulator. Design of the compliance control algorithm for the FREND arm is described. Analysis showing how to match the mass properties of a free–floating spacecraft with an air–bearing mass sled are presented. Results of testing the ability of FREND to grapple an appropriately designed air bearing sled with mass and inertia properties similar to a geosynchronous satellite are presented.