Variable Length Sling Load Hoisting Control Method

This work presents an active variable length sling load hoisting control strategy for retrieving a low-mass payload. Nonlinear planar oscillations of a rigidly suspended mass are described by a fully nonlinear dynamic model that incorporates variable length actuation. The control strategy lengthens the cable when the payload is near the vertical line, shortens the cable when the payload approaches maximum swing angle, and is otherwise free swinging. A genetic-like algorithm is adopted to estimate optimal control parameters. The controlled system is simulated via time integration of the nonlinear equations of motion showing that a payload attached to a 32 m cable released from rest at 15 deg is stabilized to 5 deg and hoisted to 1.8 m in 300 s.