title: Outperforming hummingbirds' load-lifting capability with a lightweight hummingbird-like flapping-wing mechanism.
abstract: The stroke-cam flapping mechanism presented in this paper closely mimics the wing motion of a hovering Rufous hummingbird. It is the only lightweight hummingbird-sized flapping mechanism which generates a harmonic wing stroke with both a high flapping frequency and a large stroke amplitude. Experiments on a lightweight prototype of this stroke-cam mechanism on a 50 mm-long wing demonstrate that a harmonic stroke motion is generated with a peak-to-peak stroke amplitude of 175° at a flapping frequency of 40 Hz. It generated a mass lifting capability of 5.1 g, which is largely sufficient to lift the prototype's mass of 3.39 g and larger than the mass-lifting capability of a Rufous hummingbird. The motor mass of a hummingbird-like robot which drives the stroke-cam mechanism is considerably larger (about five times) than the muscle mass of a hummingbird with comparable load-lifting capability. This paper presents a flapping wing nano aerial vehicle which is designed to possess the same lift- and thrust-generating principles of the Rufous hummingbird. The application is indoor flight. We give an overview of the wing kinematics and some specifications which should be met to develop an artificial wing, and also describe the applications of these in the mechanism which has been developed in this work.
authors.affiliation: Department of Mechanical Engineering,  Katholieke Universiteit Leuven, Celestijnenlaan 300, Box 2420, Leuven 3001, Belgium Frederik.Leys@kuleuven.be.
authors.forename: Frederik
authors.identifier: http://orcid.org/0000-0002-3461-0734
authors.initials: F
authors.lastname: Leys
authors.affiliation: Department of Mechanical Engineering,  Katholieke Universiteit Leuven, Celestijnenlaan 300, Box 2420, Leuven 3001, Belgium.
authors.forename: Dominiek
authors.initials: D
authors.lastname: Reynaerts
authors.affiliation: Department of Mechanical Engineering,  Katholieke Universiteit Leuven, Celestijnenlaan 300, Box 2420, Leuven 3001, Belgium.
authors.forename: Dirk
authors.initials: D
authors.lastname: Vandepitte
keywords: Flapping; Lightweight; Mechanism; Rufous hummingbird; Stroke-cam; Trochilidae; Wing