Solid State Adaptive Rotor Using Postbuckled Precompressed, Bending-Twist Coupled Piezoelectric Actuator Elements

Abstract

This paper is centered on a new actuation mechanism which is integrated on a solid state rotor. This paper outlines the application of such a system via a Post-Buckled Precompression (PBP) technique at the end of a twist-active piezoelectric rotor blade actuator. The basic performance of the system is handily modeled by using laminated plate theory techniques. A dual cantilevered spring system was used to increasingly null the passive stiffness of the root actuator along the feathering axis of the rotor blade. As the precompression levels were increased, it was shown that corresponding blade pitch levels also increased. The PBP cantilever spring system was designed so as to provide a high level of stabilizing pitch-flap coupling and inherent resistance to rotor propeller moments. Experimental testing showed pitch deflections increasing from just 8 • peak-to-peak deflections at 650 V/mm field strength to more than 26 • at the same field strength with design precompression levels. Dynamic testing showed the corner frequency of the linear system coming down from 63 Hz (3.8/rev) to 53 Hz (3.2/rev). Thrust coefficients manipulation levels were shown to increase from 0.01 to 0.028 with increasing precompression levels. The paper concludes with an overall assessment of the actuator design.

Review of shape-morphing automobile structures: concepts and outlook

“…131,132 One successful solution for improving the performance of PZT materials is the design of structures consisting of postbuckled pre-compressed members which magnify both the control defections and the control forces of PZT patches simultaneously. 133,134 Axial pre-compression was applied to a PZT actuator at the trailing edge of a small unmanned aerial vehicle wing using a stretched elastic skin covering the outside of the wing. 135…”

Design space of embeddable variable stiffness bi-stable elements for morphing applications

“…Most of the underlying mechanisms rely on coupling several physical domains, rendering the approaches active or semi-active. Alternatively, stiffness adaptation capacity can originate in the structurally elastic phenomena of buckling [7][8][9][10][11][12][13][14][15][16][17] and multi-stability [18][19][20][21][22][23][24][25].…”

Concept for morphing airfoil with zero torsional stiffness

“…Such concepts have included using pairs of pre-compressed springs attached to the blade root to null the passive stiffness of a root actuator along the feathering axis [24]. Another means to manipulate blade stiffness is to create a discontinuity in the external skin at the trailing edge where an actuated screw thread is attached.…”