Patent ID: 7044314

Claim:
A method of reducing pendulations of cargo hoisted by cranes mounted on moving platforms, comprising the steps of: calculating an operator-input position of a boom tip of the crane; determining a relative motion of the cargo suspended from a hoisting cable of the crane with respect to a suspension point of the hoisting cable of the crane; providing in-plane and out-of-plane delays and gains based on the relative motion of the cargo; calculating a correction to a motion commanded by the operator in an inertial frame based on the in-plane and the out-of-plane delays and gains; calculating reference angles for a boom of the crane based on a correction to the operator desired position of the boom tip and a motion of the moving platform in order to provide damping to reduce cargo pendulation, where at least one of the following relationships exists: A) a position of the boom tip is measured relative a moving platform fixed coordinate system (x″, y″, z″); B) a moving platform fixed position of the boom tip is transformed into an inertial coordinate system (x, y, z) using a series of roll (Φ roll ) and pitch (Φ pitch ) rotation matrices, and a vector describing a moving platform sway x, surge u, and heave h motions; C) a reference inertial motion of the boom tip X ref and Y ref in the inertial coordinate system is calculated by adding a correction to operator inertial commands x p and y p according to a delayed feedback control algorithm; D) the operator inertial commands isolate platform motion and a delayed-position feedback correction produces damping of the payload pendulations; E) a reference luff β and slew α angles are calculated using the inertial platform motion generate an inertial reference position of the boom tip x ref and Y ref and isolate motion of the platform from reaching the boom tip; F) the reference luff and slew angles are platform motion isolators; and G) the boom tip is the suspension point of the payload hoist line.