Design and Testing of a Biologically Inspired Pneumatic Trailing Edge Flap System

Abstract

In this study a novel, biologically inspired, trailing edge flap system was designed and tested under full-scale aerodynamic loading in the Glenn L. Martin Wind Tunnel at the University of Maryland. The system consisted of two pairs of pneumatic artificial “muscles” driving a flap through wire rope “tendons.” This concept is envisioned to be a next generation high performance actuation system applicable to a wide range of control surfaces from UAV flaps to rotorcraft blades. In order to explore the feasibility and design of this concept, a representative wing section with a partial-span trailing edge flap was constructed. A 15% chord flap 10-in long was installed into a 24-in span wing with a 21-in chord NACA 0012 airfoil. Two pairs of antagonistically arranged 1-in outer diameter, 5.25-in length pneumatic artificial muscles were mounted chordwise inside the wing section. A novel tendon spooling design was used to convert the actuation forces into torques about the flap spar. A simple empirical model was developed which successfully predicts low frequency performance. System performance was experimentally determined over a wide range of operating pressures (15 – 90 psi), actuation frequencies (0.1 – 40 Hz), angles of attack (0 – 12°), and free stream velocities (M = 0 – 0.3). This actuation concept was successfully able to generate large flap deflections (almost ± 40°) and show that biologically inspired pneumatic actuation systems are a promising technology for future aerospace control applications.