<title>SMA actuator for tab-assisted control surface application</title>

Abstract

This study, started in late 1997, evaluates the concept of tab-assisted control (TAC), and the use of shape memory alloy (SMA) actuator in that connection. Under the TAC concept, a small tab, typically 10 percent of the mean chord of the entire control surface structure, is appended to the trailing edge of the primary control surface, or flap. This small tab vastly enhances the versatility of the control surface system. Depending on the orientation of the tab with respect to the flap and the amount of tab deflection, this tab may be used to modify lift and torque, actuate the flap, or provide precision control; if the tab is aligned with the flap, TAC reverts itself to the conventional configuration. Despite its many benefits, TAC faces one practical challenge in implementation. Due to the particular TAC configuration, the actuating system for the tab must be compact enough to fit in the limited real estate available within the flap. This makes SMA actuator a promising contender for TAC implementation. This paper presents some of the experimental result relevant to the design of the SMA actuator and addresses implementation issues such as power usage, life cycle, frequency response, and reliability.