Bioinspired pitch control using a piezoelectric horizontal tail for rudderless UAVs

A bird's tail plays a crucial role in flight dynamics by making rapid fine-tuned movements for precise attitude stabilization in addition to large scale deformations used in conjunction with the wings to achieve prolonged maneuvers. However, this control surface geometry differs substantially from those of traditional aircraft such as the vertical rudder which has slower actuation times, less versatility relative to control authority, and increased radar signatures. The current work aims to increase maneuverability in rudderless UAVs using Macro Fiber Composites (MFCs) and multi-material 3D printing to achieve a bidirectional camber morphing horizontal tail. The MFCs are customized with a 55° fiber orientation to achieve bending-twisting coupling resulting in complex curvatures. Previous work investigated the actuator's capabilities to control yaw and act as an air break during sideslip. The current work investigates the actuator's ability to control pitch and also analyzes its effectiveness as a rudder during changes in angle of attack. The control effectiveness was assessed via wind tunnel experiments of a full bodied bioinspired UAV of 0.34m wing span with active horizontal tail. Alpha sweeps were conducted across a range of wind speeds. While the complex curvature of the actuator is desirable for control of both yaw and pitch, it also causes coupling between these two degrees of freedom. The magnitude of this coupling is also investigated.