US 5,961,563 A · Anti-sway control for rotating boom cranes

Abstract

A process for anti-sway control of a rotating boom or other three-degree-of-freedom crane wherein the load is hoisted, at variable hoist lengths, by a cable suspended from a point that can be moved in space in three dimensions, either freely, or under known constraints. Initial acceleration of the load induces an initial sway to the load. A second lateral acceleration, equal to the first lateral acceleration, is scheduled to be applied one-half a sway period later to remove the sway induced by the first acceleration. A third acceleration is applied to correct for half the excess sway induced by hoisting, by non-linearities in the pendulum, and by crane platform motion; and a forth acceleration, of equal magnitude as the third but in the opposite direction, is scheduled for one-half a sway period later, to correct the remaining half of the excess sway energy. The first and third accelerations are constrained by the ability of the crane to execute them and to execute the delayed second and fourth accelerations. The lateral accelerations are applied additively, and repeated sequentially at a variable rate, to accelerate the load from its initial location to objective velocities and locations under controlled anti-sway conditions.

Claims3

Dependent claims

A method for controlling the motion of a crane supported, movable suspension point for a load suspended at a variable hoist length therefrom, to meet an arbitrary horizontal velocity reference while preventing sway of the load, by employing a computer-controlled control law and comprising the steps of:

(a) utilizing computer controls for moving the suspension point to accelerate the suspended load from an initial velocity to a second velocity and inducing an initial sway to the load when initially moved,
(b) scheduling a first lateral anti-sway acceleration vector, to be applied one-half a sway period late, to damp the sway induced by the initial load attachment point acceleration,
(c) determining an immediate lateral correction acceleration vector to reduce by a factor of one-half the sway energy contributed by (1) hoisting the load while swaying, (2) non-linearities in the pendulum load motion, (3) crane platform motion, and (4) external forces,
(d) scheduling a second lateral anti-sway acceleration, having the same magnitude as the correction acceleration but in the opposite direction, to be applied one-half a sway period later to correct the remaining half of the excess sway energy,
(e) applying, additively, at the designated times, the lateral accelerations of steps (a) through (d) to accelerate the load attachment point,
(f) repeating each of steps (a) through (e) at a sampling interval proportional to the sway period.

3 more elements

Dependencies are inferred from the claim text.

Anti-sway control for rotating boom cranes

Life of this patent

Anti-sway control for rotating boom cranes

Life of this patent

Abstract

Claims3