  Flying vertebrates exhibit sophisticated wingbeat kinematics. Their
specialized forelimbs allow for the wing morphing motion to couple with the
flapping motion during their level flight, Previous flyable bionic platforms
have successfully applied bio-inspired wing morphing but cannot yet be
propelled by the morphing-coupled wingbeat pattern. Spurred by this, we develop
a bio-inspired flapping-wing aerial vehicle (FWAV) entitled RoboFalcon, which
is equipped with a novel mechanism to drive the bat-style morphing wings,
performs a morphing-coupled wingbeat pattern, and overall manages an appealing
flight. The novel mechanism of RoboFalcon allows coupling the morphing and
flapping during level flight and decoupling these when maneuvering is required,
producing a bilateral asymmetric downstroke affording high rolling agility. The
bat-style morphing wing is designed with a tilted mounting angle around the
radius at the wrist joint to mimic the wrist supination and pronation effect of
flying vertebrates' forelimbs. The agility of RoboFalcon is assessed through
several rolling maneuver flight tests, and we demonstrate its well-performing
agility capability compared to flying creatures and current flapping-wing
platforms. Wind tunnel tests indicate that the roll moment of the asymmetric
downstroke is correlated with the flapping frequency, and the wrist mounting
angle can be used for tuning the angle of attack and lift-thrust configuration
of the equilibrium flight state. We believe that this work yields a
well-performing bionic platform and provides a new actuation strategy for the
morphing-coupled flapping flight.
