Pitching moment generation for longitudinal attitude control of insect-mimicking flapping-wing system

Abstract

Summary form only given. Insects have been a good model to get some inspirations for development of insect-mimicking flapping-wing micro air vehicles (FW-MAVs). With no control surface at tail, insects change their flight attitude by changing flapping stroke plane and amplitude in both wings. Most birds produce useful aerodynamic forces during the downstroke. Unlike birds, insects create the flight force even in upstroke as well as in downtroke by flipping over the wing surfaces at the end of each stroke [1]. In addition, they flap their wings with large flapping angle at higher freqencies than birds [2]. These features can be used for creating designs for insect-mimicking FW-MAVs. To possess the inherent stability, insect-mimicking FW-MAVs should be able to create very sysmmetric aerodynamic forces in the left and right wings to prevent rolling motion because they do not have control surfaces at the tail. In addition to this, the system should be assembled such that pitching moment is zero around its center of gravity [3]. There are some insect-mimicking flapping-wing systems found in the literature survey [4, 5]. The flapping-wing system recently demonstrated a controlled flight by applying electric power from an external power supply [4]. The hummingbird-mimicking FW-MAV seems to be only successful system that demonstrated remotely controlled flight without tail controllers [5]. We also have been developing an insect-mimicking flapping-wing system, which mimics flight of a beetle, Allomyrina Dichotom, [6] and can vertically take off without any guide wires and control system, which means that the system has inherent pitching stability at the early period of takeoff [7]. The system has a transmission with a gear ratio of 12: 1 and requires a pair of Li-polymer batteries. In this work, we present a mechanism, which can change the flapping angle range, for vertical and longitudinal flights in our insect-mimicking flapping-wing system. Firstly, we describe how we design and fabricate the mechanism and wings. The force produced by the system was estimated by the unsteady blade element theory (UBET) and experimented by a load cell measurement. Subsequently, we successfully demonstrated stable takeoff of the FW-MAV powered by installed batteries and a remote power control system. Finally, we evaluated the pitching moment generation of the flapping-wing system with the mechanism.