Whirl Testing of a Pneumatic Artificial Muscle Driven Helicopter Trailing Edge Flap

The purpose of this study was to investigate the feasibility of using Pneumatic Artificial Muscles (PAMs) as the driving element of a trailing edge flap for vibration mitigation applications in rotorcraft, with potential extensions to include primary control. PAMs are a promising alternative to both classical actuation technologies and smart structure based approaches due to their light weight, large force and stroke capabilities, and their simple design. A prototype PAM actuation system was designed and built to dynamically drive a hypothetical trailing edge flap for a UH-60 main rotor blade. This system was then scaled down (primarily in span) to allow for testing under full-scale centrifugal loading in the 10-ft diameter vacuum whirl chamber at the University of Maryland. Full-scale aerodynamic hinge torques were simulated using linear springs at a constant moment arm. Additionally, full-scale inertial loading of the flap was also simulated using an added inertial mass. The prototype system was tested over a wide range of operating conditions and was successfully able to achieve ±8° of deflection quasi-statically for a simulated 10% span, 15% chord flap centered at 0.75R. As desired, there was no degradation in performance with increasing centrifugal loading up to the design point of 457 g. There was a significant loss of performance with increasing actuation frequency, however; this was due to an insufficiently large air supply system mounted in the vacuum chamber. These experiments successfully demonstrated that PAMs show great promise for trailing edge flap actuation on full-scale rotorcraft.