US Patent 9016432 Descent control device

A descent control device for controlling rotational motion of an object includes: at least one drive assembly for rotationally engaging the rotating object; a first substantially planar ferromagnetic moving element in rotationally locked engagement with at least one drive assembly and comprising at least one recess formed in a surface thereof having at least one magnet fixedly disposed therein; a second substantially planar ferromagnetic moving element in rotationally locked engagement with at least one drive assembly, and comprising at least one recess formed in a surface thereof having at least one magnet fixedly disposed therein; and at least one conducting plate disposed proximate the first and second moving elements. A magnetic field may be induced by rotational movement of the first or second moving element relative to at least one conducting plate in a direction to oppose acceleration of at least one drive assembly as it rotationally engages the object.