Experimental study of a micro air vehicle with a rotatable tail

TLDR: In this article, a rotatable tail mechanism was applied to a small unmanned aerial vehicle and measured force and moment coefficient measurements for the actual vehicle at a typical flight speed indicated that a rotable tail provided a sufficient yaw moment for turning.

Abstract: An experimental study of a rotatable tail mechanism applied to a small unmanned aerial vehicle was performed using a six-component wind-tunnel balance in the U.S. Air Force Institute of Technology low-speed wind tunnel. Attributes of the control and stability characteristics of the original vehicle, which were documented in an earlier study, are compared with those of a unique control methodology, a tail consisting of a single surface, with controllable elevation and rotation. An advantage of this change is a reduction in the storage length of the vehicle. Because there are similarities in the rotatable tail mechanism and the tail of many birds, the rotatable tail reflects a biomimetric feature. Measured force and moment coefficient measurements for the actual vehicle at a typical flight speed indicated that a rotatable tail provides a sufficient yaw moment for turning. For example, yaw moment coefficients C n , ranging from -0.02 to +0.02, which is typical for a rudder, were achievable as long as the absolute value of the tail elevation angle was large. The dependence of the yaw moment coefficient on the elevator angle and angle of attack, in addition to the tail rotation angle, indicates that there would be significant challenges in applying a robust flight control scheme with the current actuator configuration. An additional feature of the tail design is that by deflecting the tail upward, it could also function effectively as an air brake. A more than twofold increase in drag coefficient for constant angle of attack was measured when the tail elevation angle was increased to nearly 70 deg.