Hoist Load Stabilization via Torque-Based and Retraction-Speed Control Systems

The purpose of this research was to develop a control law to effectively, rapidly, and efficiently stabilize an oscillating litter in helicopter hoist load operations. A model of a variable length pendulum was used in MATLAB to simulate various control models. A control system using an external torque producing device was developed and successfully controlled the system. An additional control system was developed to stabilize oscillations by controlling the speed of cable retraction. The method involved retraction at the cable's maximum displacement and extension at its maximum velocity. This control method was less efficient than the torque production method, however it still successfully decreased the angular displacement.

I. Introduction

Medical Evacuation (MEDEVAC) helicopters provide aid and rescue causalities in high-risk environments with limited time and little room for error. Due to a variety of forces such as wind, rotor wash, helicopter turns, ascents and descents, the hoist cable may sway the litter and casualty back and forth uncontrollably. This swaying makes it harder for the helicopter to maneuver in dangerous environments and compromises the casualty's safety [1]. Fig. 1.

HH-60 MEDEVAC by CPT J. Hughes.