Dynamic analysis of the cable array robotic crane

Abstract

Offshore loading and unloading of cargo vessels and on board cargo relocation during conditions of Sea State 3 or greater have been found to be difficult with existing crane technology due to oscillation of the payload. A new type of crane which uses four actuated cables to control the motion of the payload is presented. The closed chain configuration will intuitively provide more stability with respect to the motion of the sea compared to existing cranes. The kinematics and dynamics are derived using cable coordinates. Since there are four cables and three degrees of freedom, the system is redundant. This problem is solved by applying a geometric constraint to the equations of motion such that the reduced number of equations equals the degrees of freedom. The force distribution method is applied using linear programming to solve for the required cable tensions. Simulation results showing cable tensions and cable lengths during a typical crane operation are presented.