Grappler control system for a gantry crane

摘要

A system and process are provided for controlling motion of a grappler of a gantry crane to avoid damaging an object to be lifted. In an embodiment, a speed of grappler movement is automatically reduced when in close proximity to the object. Furthermore, the grappler automatically stops when positioned appropriately to permit a latching mechanism to engage the object for lifting. Normal speed grappler motion is restored when the latching mechanism is fully engaged. In a particular embodiment, the grappler includes a plurality of height sensors at various positions along the grappler to determine the respective height of the grappler above a top of the object. Vertical motion of front and rear ends of the grappler are independently actuated and controlled to permit appropriate control when the grappler and/or the object are not level.