The Beam Assembly Teleoperator (BAT)
The Beam Assembly Teleoperator (BAT) was designed to assemble the same structure used by the Space Systems Laboratory for the Experimental Assembly of Structures in EVA (EASE) program. EASE involved two pressure-suited subjects repeatedly assembling a six-element tetrahedral truss, and included both neutral buoyancy simulation and a shuttle flight experiment flown on STS 61-B in late 1985. By choosing as a design case to assemble this same structure, direct comparisons could be made between EVA and the telerobotic assembly, as well as correlation to the flight experiment. This structure was designed to be challenging for EVA assembly; no major modifications in the structure were allowed for simplifying the task for robotic assembly. Thus, BAT was designed from the outset to be as capable as EVA for this one specific assembly task, and generically capable of a variety of other EVA tasks as well.
The basic design of BAT was based on a self-contained mobility base, with vision and manipulation systems attached. The mobility base contained the control electronics, on-board power supplies, and the other support systems, as well as eight electrically-powered ducted propellers for underwater motion. Careful attention has to be paid to simulation fidelity in the neutral buoyancy environment, and floatation panels and trim weights were attached to the base unit to adjust the centers of buoyancy and gravity to be coincident, such that the vehicle has no preferred orientation. In the current configuration, BAT is equipped with two pairs of stereo monochrome video cameras, one five degree of freedom dexterous general purpose manipulator, a non-articulated grappling arm for grasping the structure under assembly, and a specialized manipulator for performing the coarse alignment task for the long struts of the truss assembly. This combination of a flexible, generalized manipulator and "pick and place" specialized manipulator for selected tasks proved to be a useful approach to the design of a structural assembly telerobot.