Post-buckled precompressed piezoelectric flight control actuator design, development and demonstration

• Published in: Smart materials and structures Vol. 15; no. 5; pp. 1323 - 1331
• Main Authors: Barrett, Ron, McMurtry, Ross, Vos, Roelof, Tiso, Paolo, De Breuker, Roeland
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.10.2006; Institute of Physics
• Subjects: Buckling; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics; Solid mechanics; Structural and continuum mechanics; Measurement; Energy consumption; Empennage; Axial force; Grid; Control synthesis; Flight control; Modeling; Piezoelectric actuators; Piezoelectricity; Axial load; Buckling; Static test; Assembly; Bimorph transducer; Stratified material; Piezoelectric sensor; Prestress; Quasi static theory; Fin; Experimental study; Weight; Postbuckling; Plate; Solid state; Non linear effect; Structural analysis; Electromechanical properties
• ISSN: 0964-1726; 1361-665X
• DOI: 10.1088/0964-1726/15/5/022

This paper describes a new class of flight control actuators using post-buckled precompressed (PBP) piezoelectric elements. These actuators are designed to produce significantly higher deflection and force levels than conventional piezoelectric actuator elements. Classical laminate plate theory (CLPT) models are shown to work very well in capturing the behavior of the free, unloaded elements. A new high transverse deflection model which employs nonlinear structural relations is shown to successfully predict the performance of the PBP actuators as they are exposed to higher and higher levels of axial force, which induces post-buckling deflections. A proof-of-concept empennage assembly and actuator were fabricated using the principles of PBP actuation. A single grid-fin flight control effector was driven by a 3.5' (88.9 mm) long piezoceramic bimorph PBP actuator. By using the PBP configuration, deflections were controllably magnified 4.5-fold with excellent correlation between theory and experiment. Quasi-static bench testing showed deflection levels in excess of plus/minus 6 deg at rates exceeding 15 Hz. The new solid state PBP actuator was shown to reduce the part count with respect to conventional servoactuators by an order of magnitude. Power consumption dropped from 24 W to 100 mW, weight was cut from 108 to 14 g, slop went from 1.6 deg to 0.02 deg and current draw went from 5 A to 1.4 mA. The result was that the XQ-138 subscale UAV family experienced nearly a 4% reduction in operating empty weight via the switch from conventional to PBP actuators, while in every other measure gross performance was significantly enhanced.