Automation Infrastructure System for a Robotic 30-Ton Bridge Crane

This paper describes the sensing portion of a system used to convert an existing 30-ton bridge crane to computer control for automated placement of construction components. The system is being designed to permit either telepresent or fully autonomous assembly of representative parts of buildings and industrial plants, e.g., girders, tanks, and pipes. In order to achieve six degree-of-freedom manipulation of the components, the traditional crane cable and hook have been replaced by TETRA, an inverted cable-operated Stewart platform equipped with various manipulators. The sensing systems are primarily displacement, force, and other state sensors. What makes this application unique is the scale of the robot: the crane's workspace is 40 m long, 23 m wide, and 24 m high — a volume of more than 10,000 cubic meters. This scale, and the need to operate without wires has led to a control system based on wireless packet communication by intelligent modules known as "smart pods." The pods interface to one or several force, displacement, or state sensors. The pods broadcast their data via wireless ethernet to base stations which then communicate with the world via higher-speed networks. The present paper discusses issues relating to the architecture of the sensor array needed to operate this large construction robot and the communications infrastructure needed to supply that information to remote sites in real time.