Recent Simulation Conclusions for Damped-oscillation Control of Cranes

When suspended payloads are moved with an overhead crane, pendulum like oscillations are naturally introduced. This presents a problem any time a crane is used, especially when expensive and/or delicate objects are moved, when moving in a cluttered and/or hazardous environment, and when objects are to be placed in tight locations. For example, one nuclear waste-handling operation examined by the U.S. Department of Energy (DOE) Oak Ridge National Laboratory (ORNL) is the transportation of heavy objects such as waste storage casks or barrels from one location to another through cluttered process facility environments or storage facilities. Typically, an object is lifted by a crane hook on the end of a cable, creating a pendulum that is free to swing during transit. This swinging motion makes remote positioning of casks or barrels difficult to control precisely and is potentially destructive to facility equipment and to other storage containers. Typically, a crane operator moves objects slowly to minimize induced swinging and allow time for oscillations to dampen, maintaining safety but greatly decreasing the efficiency of operations. Using damped-oscillation control algorithms is one approach to solving this problem. This paper summarizes recent simulation results in damped-oscillation-type control algorithms. It also discusses practical implementation issues including control algorithm robustness to payload length changes, hardware requirements for implementation of the control algorithms, and system limits on Coulomb friction. 1.0 INTRODUCTION AND BACKGROUND Damped-oscillation control algorithms have been demonstrated over the past several years on laboratory-scale robotic systems, on medium-scale gantry robots, and on full-scale overhead cranes. Damped-oscillation crane control was first implemented on a laboratory-scale test at the Sandia National Laboratories using a CIMCORP XR 6100 gantry robot, a 50-lb weight, and an 80-in. cable. This class of algorithms was further analyzed in Singer and Seering, Singhose and Singer, Petterson et al., and Singhose et al. ORNL implemented a damped-oscillation algorithm on a full-scale crane. Work on these types of control algorithms is still an active area of research today (see for example). Some of the past implementations of damped-oscillation control on crane-like systems had two