Sling Load Stabilization

Helicopter sling-loads greatly increase logistical efficiency in military and civilian applications. There are, however, significant risks associated with swinging and oscillating sling loads, which present danger to aircrafts and their crews. The Army Future Vertical Lift project is expected to greatly increase helicopter airspeeds, which amplifies the dangers of unstable sling loads. Input shaping is a control approach that is used on a variety of systems, such as Gantry cranes, and has been attempted for sling-load systems in the past. Input shaping can be implemented via a helicopter's Stability Augmentation System. To test the effectiveness of input shaping on helicopter sling-load systems, a model is developed to simulate helicopter and load movement for a sling-load system subject to external forcing. The input-shaped results using state feedback control show marginal stability of the load and significant residual movement of the aircraft. Using PID control, the input-shaped results show stability after a significant settling time, and greater helicopter movement than the state feedback control. Model development, simulation results and analysis are presented.