Testing and System Identification of an Ornithopter in Longitudinal Flight

Abstract

There is currently a large effort underway to understand the flight dynamics of avian-based flapping-wing vehicles, or ornithopters, as they represent a critical intersection between existing biological flyers and the need for small aerial robots to conduct a variety ofmission scenarios. Efforts tomodel the flight dynamics of these vehicles for feedback control have been complicated by a number of factors including nonlinear flight motions, unsteady aerodynamics at lowReynolds numbers, and limited sensor payload capacity. This paper presents data for a 0.45 kg ornithopter research platform, flown in straight and level mean flight. A visual tracking system was employed to follow retroreflective markers on the ornithopter and reconstruct state measurements. A multibody model of the flight dynamics was used to investigate the spatial distribution of kinematic variables over the duration of a wing stroke, and system identification techniqueswere employed to extractmodels for the lift, thrust, andpitchingmoment coefficients. Two methods of parameter estimation showed good results for relatively simple aerodynamic models that can be used for feedback control.