GLOBAL CONTROL OF SUSPENSION FORCES FOR MICROGRAVITY SIMULATION

LARGE PRECISION SPACE STRUCTURES ARE BEING CONCEIVED TO ACCOMPLISH AIR FORCE SPACE OBJECTIVES IN THE 1990'S AND BEYOND. SOME OF THE STRUCTURES ARE HUNDREDS OF METERS IN DIMENSION AND WILL BE REQUIRED TO MAINTAIN SHAPE AND ALIGNMENT TO WITHIN MICRONS. OTHER TYPES OF STRUCTURES WILL BE SMALLER, STIFFER, AND WILL BE REQUIRED TO SLEW RAPIDLY, ACHIEVE POINTING ACCURACIES ON THE ORDER OF MICRORADIANS, AND LIMIT JITTER TO NANORADIANS. IN BOTH CASES, CONTROL SYSTEMS WILL REQUIRE ACCURATE STRUCTURAL MODELS. INITIAL DEVELOPMENT OF THE CONTROLLERS WILL REQUIRE EXTENSIVE GROUND TESTING, BOTH TO VERIFY THE STRUCTURAL MODELS AND TO VERIFY THE PERFORMANCE OF CONTROL SYSTEMS. THESE STRUCTURES MAY BUCKLE IF THEY ARE NOT PROPERLY SUPPORTED, AND THEIR MODAL CHARCTERISTICS CAN BE DISTORTED BY GEOMETRIC STIFFNESS WHICH IS PROPORTIONAL TO GRAVITY. DISTRIBUTED SUSPENSION SYSTEMS WILL BE REQUIRED TO MINIMIZE GRAVITY-INDUCED STIFFNESS WITHOUT CONSTRAINING THE MOTION OF THE STRUCTURE. THIS PROPOSAL CONCERNS THE DEVELOPMENT OF A MULTI-INPUT MULTI-OUTPUT (MIMO) CONTROL SYSTEM FOR THE GLOBAL CONTROL OF A MULTI-CABLE SUSPENSION SYSTEM. PHASE I IS LIMITED TO SMALL AMPLITUDE CONSIDERATIONS; PHASE II WILL CONSIDER LARGE AMPLITUDE APPLICATIONS AS WELL.