Travelling crane for unloading ship - has grab sway prevented by alternate acceleration and deceleration of trolley

摘要

A travelling crane (51) has a grab (54) whose oscillations are damped by controlling the speed of travel of the trolley (52) using electronic circuit. The trolley is made to move with a sinusoidal acceleration and deceleration at a frequency which corresponds to the natural frequency of oscillations of the grab (54) at the end of the cable (53). The oscillations of the grab (54) are thus cancelled by the motion of the trolley (52).