FINITE-ELEMENT DESIGN OF MANIPULATOR-COUPLED SPACECRAFT FOR A RESEARCH TESTBED

This paper describes the design and analysis of a research testbed dev eloped to study the control of manipulator-coupled spacecraft with ind ependent attitude control systems. This scenario could present itself in the assembly of Space Station Freedom (SSF). SSF assembly calls for a rendezvous of the Space Shuttle (SS) with SSF Part of the assembly process requires that both spacecraft be coupled via the Space Shuttle Remote Manipulator System. An additional criterion that poses increas ed complexity is that the Space Shuttle controls and Space Station con trols can not communicate. The technical issue involved is unwanted vi brations of the coupled-configuration that occur retraction and the co mplications due to non-interacting control systems. To understand thes e vibrations and possible complications, a research testbed has been b uilt at the Marshall Space Flight Center in Huntsville, AL. To build t he testbed, the manipulator links joints, and vehicles that represent the Space Shuttle and Space Station had to be designed. Pre-design sim ulation studies using ANSYS [1] (a Finite Element Computer Code) is us ed to size and design the manipulator links for the experimental facil ity. The ANSYS results were verified by the development of the Lagrang ian Equations of motion. The Harmonic drives used as joints for the tw o link, three joint manipulator have been dissected into free body dia grams to ensure proper load paths in the ANSYS models. Accurate simula tion of manipulator-coupled spacecraft is an important technology for NASA to understand. This paper outlines the methodology behind the pre liminary design of a research testbed developed to help NASA gain know ledge in this area.