Flying animals both power and control flight by flapping their wings. This enables small natural flyers such as insects to hover close to a flower but also to rapidly escape danger. Animal flight has always drawn the attention of biologists, who not only study their complex wing motion patterns and aerodynamics but also their sensory and neuro-motor systems during such agile maneuvers. Recently, flying animals have also become a source of inspiration for robotics researchers, who try to develop lightweight flying robots that are agile, power-efficient, and even scalable to insect sizes.

The DelFly Nimble in stationary (hovering) flight. (Henri Werij, TU Delft)
The robot is equipped with two independent flapping mechanisms — one for each wing pair on the sides of the robot. These are complemented with two rotary servo actuators — one adjusting the dihedral angle by changing the relative orientation of the two flapping mechanisms and the other actuating the tips of the left and right wing-pair roots.

Researchers have developed the DelFly Nimble, a novel insect-inspired flying robot with flapping wings, beating 17 times per second, that not only generate the lift force needed to stay airborne but also control the flight via minor adjustments in the wing motion. Inspired by fruit flies, the robot’s control mechanisms have proved to be highly effective, allowing it not only to hover on the spot and fly in any direction but also be very agile.

The robot has a top speed of 25 km/h and can perform aggressive maneuvers such as 360-degree flips, resembling loops and barrel rolls. The 33-cm wingspan and 29-gram robot has, for its size, excellent power efficiency, allowing five minutes of hovering flight, or a flight range of more than 1 km, on a fully charged battery. The robot has a thrust-to-weight ratio of more than 1.3 and is capable of carrying an additional payload of up to 4 grams (e.g. a camera system with a live video feed, additional sensors, etc.) The exceptional agility can be demonstrated by 360-degree flips around the pitch or roll axes or rapid transitions from hover to forward or sideways flight, and vice versa. At full throttle, the robot reaches a top speed of 7 m/s (~25 km/h).

Like in quadrotors or helicopters, but also like in insects, forward/backward and sideways flight is achieved by pitching and rolling the robot’s body into the respective direction. To control the body orientation (attitude), the robot needs to be able to produce torques around the three orthogonal body axes. To this end, the robot is equipped with two independent flapping mechanisms — one for each wing pair on the sides of the robot. These are complemented with two rotary servo actuators — one adjusting the dihedral angle by changing the relative orientation of the two flapping mechanisms and the other actuating the tips of the left and right wing-pair roots. Rolling is achieved by driving the two wing pairs at different flapping frequencies, which results in a thrust difference creating the torque around the roll axis.

The robot has potential for novel applications as it is lightweight, safe around humans, and able to fly more efficiently than more traditional drone designs, especially at smaller scales.

For more information, contact Mat j Karásek at This email address is being protected from spambots. You need JavaScript enabled to view it.; +31 6 8384 1669.

Tech Briefs Magazine

This article first appeared in the November, 2019 issue of Tech Briefs Magazine.

Read more articles from this issue here.

Read more articles from the archives here.