Folding wingtips address the challenges of high aspect ratio wings, such as airport conformity, increased wing root bending moment, and reduced aircraft maneuverability. The functionalities of free-flapping folding wingtips can be extended with multifunctional wingtip actuators that allow for active adjustment of the wingtip’s cant angle and hinge stiffness. The objective of this paper is the identification of governing factors influencing the adaptive-stiffness characteristics of pneumatic rotary actuators. The authors experimentally determine the characteristics of such a commercially available pneumatic rotary actuator and formulate analytical equations for actuator moment and stiffness as well as the wingtip’s natural frequencies. The actuator characteristics can be accurately described by an isobaric or adiabatic process, depending on the pneumatic setup. The pneumatic actuator exhibits zero stiffness in a pressure-regulated mode, whereas targeted adjustment of the actuator stiffness is possible by shutting off the mass flow into the actuator chambers. The formulated equations allow a detailed design of multifunctional wingtip actuators for application in highly efficient high aspect ratio aircraft. The findings of this study can be transferred to hydraulic rotary actuators, which would be required to achieve the necessary load-bearing capacity for application in larger transport aircraft.
P. Meyer, M. Sprengholz, H. Traub, C. Hühne
Adaptive-Stiffness Characteristics of Pneumatic Rotary Actuators for Folding Wingtips
ASME 2024 Aerospace Structures, Structural Dynamics, and Materials Conference, (2024) [Link]