An at-scale tailless flapping wing hummingbird robot. II. Flight control in hovering and trajectory tracking.

Flight control is a challenging task, such as stable hovering and trajectory tracking of tailless Flapping-Wing Micro Aerial Vehicles (FWMAVs). Given the constraint on actuation capability, the flight control authority is limited beyond sufficient lift generation. In addition, the highly nonlinear and inherently unstable vehicle dynamics, unsteady aerodynamics, wing motion caused body oscillations, and mechanism asymmetries and imperfections due to the fabrication process all pose challenges to flight control. We propose a systematic onboard control method to address such challenges in this work. In particular, with a systematic comparative study, a nonlinear flight controller incorporating parameter adaptation and robust control demonstrates the preferred performances. Such a controller is designed to address time-varying system uncertainty in flapping flight. The proposed controller is validated on a 12-gram at-scale tailless hummingbird robot equipped with two actuators. Maneuver experiments have been successfully performed by the proposed hummingbird robot, including stable hovering, waypoint and trajectory tracking, and stabilization under severe wing asymmetries.