Horizontal Planform Morphing Tail for an Avian Inspired UAV Using Shape Memory Alloys

Unlike most modern aircraft, which have a vertical tail component, birds fly utilizing a purely horizontal tail. In order to provide control normally associated with a vertical rudder, bird’s tails are incredibly mobile, twisting, pitching, and widening to perform necessary aerial maneuvers. This research primarily focuses on the development and testing of a mechanical planform morphing horizontal control surface, aiming to emulate the tail-spread control action of birds. This horizontal control surface is implemented on a small, tailless, avian inspired unmanned aerial vehicle (UAV). In this research, the horizontal control surface, made entirely of 3D printed material, comprises a rigid overlapping top layer held together by a soft and elastic honeycomb bottom layer, allowing for shape morphing without compromising structural integrity required to withstand aerodynamic forces. Using the relatively large strain and strength offered by shape memory alloy (SMA) springs, the 3D printed horizontal tail undergoes a notable and consistent geometric change. To quantify the system’s performance, the tail width and center was measured while actuating the springs through a range of frequencies from 0.01 to 10 Hz. Preliminary experiments were conducted in a 1ft. × 1 ft. open loop wind tunnel at the University of Michigan at wind speeds of 5, 10 and 15 m/s to quantify the effects of aerodynamic loading on actuation magnitude and speed.