Versatile control of multiple morphing surfaces of Micro Air Vehicle with reduced weight and optimized power consumption

Morphing or shape changing of aircraft, though attractive from aerodynamics point of view, entails additional weight and power penalty and control complexities that pose research challenges. Researchers generally agree with the aerodynamic benefits of morphing and propose Shape Memory Alloy (SMA) actuators for controlled morphing. However, the methods discussed in the literature, generally uses computer based software and data acquisition systems that are suitable for ground based operation. This paper presents an in-flight configurable morphing Micro Air Vehicle (MAV) with four SMA actuated morphing surfaces. As a proof of concept, NAL's 300mm MAV airframe was modified to provide deflectable leading edges and trailing edges on both left and right side wing of the MAV. These four morphing surfaces could be actuated independently. The paper also presents the weight reduction methods employed to achieve a weight budget of less than 6g per morphing system. The power optimization using staggered PID-PWM control algorithm has reduced the peak battery current drawn by four SMA actuators (apparently operating together) to that of a single SMA. Typical rate of 4.4°/s for actuating the morphing segment and 2.6°/s for deactivating the same have been achieved at a control accuracy of ±0.5°.