Traversing hoists – Having means to prevent or dampen load oscillations – Antisway
Patent
1994-12-05
1996-06-18
Merritt, Karen B.
Traversing hoists
Having means to prevent or dampen load oscillations
Antisway
B66C 1306
Patent
active
055269460
ABSTRACT:
A process employing a computer controlled crane system for controlling the motion of a movable trolley from which a load is suspended at a variable hoist length therefrom to meet a selected arbitrary horizontal velocity reference while preventing sway of the load involves the steps of first, determining a lateral acceleration to reduce by a factor of one-half the sway energy contributed by (1) hoisting a load while the load is swaying; (2) non-linearities in the pendulum motion; (3) external forces such as wind, crane motion; and (4) non-vertical lifting of the load. Second, an additional acceleration of the same magnitude, but of opposite sign, is applied one-half a pendulum period latter to correct the remaining of the excess sway energy. Next, a lateral acceleration is applied to the load to respond to velocity demand as determined by the current trolley velocity and the predicted velocity change resulting from future sway-damping acceleration, and a lateral acceleration is applied to dampen the sway induced by the trolley employing a time-delay transfer law. All of these steps are applied additively to accelerate the trolley and all steps repeated at a sampling rate proportional to the sway period of the attached load.
REFERENCES:
patent: 3351213 (1967-11-01), Newman et al.
patent: 4756432 (1988-07-01), Kawashima et al.
patent: 4997095 (1991-03-01), Jones et al.
patent: 5127533 (1992-07-01), Virkkunen
patent: 5219420 (1993-06-01), Kiiski et al.
Brahan Thomas J.
Daniel H. Wagner Associates, Inc.
Merritt Karen B.
Nelson Wallace J.
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