Post-buckled precompressed subsonic micro-flight control actuators and surfaces

Abstract

This paper describes a new class of flight control actuators using post-buckledprecompressed (PBP) piezoelectric elements to provide much improved actuatorperformance. These PBP actuator elements are modeled using basic largedeflection Euler-beam estimations accounting for laminated plate effects. Thedeflection estimations are then coupled to a high rotation kinematic model whichtranslates PBP beam bending to stabilator deflections. A test article usingPZT-5H piezoceramic sheets built into an active bender element was fitted withan elastic band which induced much improved deflection levels. Statically thebender element was capable of producing unloaded end rotations on the order of ± 2.6°. With axial compression, the end deflections were shown to increase nearly four-fold.The PBP element was then fitted with a graphite–epoxy aeroshell which wasdesigned to pitch around a tubular stainless steel main spar. Quasi-static benchtesting showed excellent correlation between theory and experiment through ± 25° of pitch deflection. Finally, wind tunnel testing was conducted at airspeeds up to 120 kts(62 m s−1,202 ft s−1). Testing showedthat deflections up to ± 20° could be maintained at even the highest flight speed. The stabilator showed no flutter ordivergence tendencies at all flight speeds. At higher deflection levels, it was shownthat a slight degradation deflection was induced by nose-down pitching momentsgenerated by separated flow conditions induced by extremely high angles of attack.