DelFly Nimble

Development of a highly agile and programmable insect-inspired flying robot. The DelFly Nimble is controlled through adjustments of the motion of its four wings. It can hover or fly in any direction: forward, backward, up, down, or sideways. The robot, featured on the cover of the Science magazine, can be used for insect flight research. 

The DelFly Nimble is a very agile insect-inspired robot that I developed during my postdoctoral research at MAVLab, TU Delft. This flying robot has four flapping wings that serve for propulsion as well as for control. Unlike the previous DelFly designs, the DelFly Nimble has no tail to stabilize the flight. Instead, the robot is equipped with an onboard computer and sensors and is actively stabilized via adjustments of the motion of its four wings. It has a wingspan of 33 cm and can hover for over 5 minutes, or cover a distance of more than 1 km, on a fully charged battery. Its exceptional agility allows fast transitions from hover to fast forward/sideways flight. The maximal forward speed is 7 m/s. The robot can carry a payload of 4 grams, such as a camera system streaming live video to the operator or additional sensors.

Bio-inspired control

The wings of DelFly Nimble are driven by two flapping mechanisms (independent for the left and right wing pair) that make the 4 wings beat 17 times per second when hovering; adjusting the flapping frequency results in climbing/descending. The robot can, like flying insects, control its rotation around its three body axes: rolling, pitching and yawing. To generate roll moments, which result in a rotation around the forward-pointing body axis (rolling motion), the robot increases the flapping frequency of the wing pair on one side and decreases the flapping frequency of the one on the other side. Rotation around the transversal axis (pitching motion) is induced by a shift of the flapping wings backward or forward, via a servo actuator adjusting the relative angle of the two flapping mechanisms. Finally, turning around the vertical axis (yawing motion) is achieved by deflecting the roots of the two wing pairs asymmetrically. As a result, the thrust force of one of the wing pairs gets tilted forward, while the other one backward, resulting in a force couple that makes the robot turn.

To fly forward/backward, the robot pitches forward/backward:

Similarly, sideways flight is achieved by rolling the body left/right:

Insect flight research

As we have shown in our Science publication, prepared in collaboration with the Experimental Zoology group at Wageningen University & Research, it can also be used in insect flight research.  The robot was able to “replay” the escape maneuvers of fruit flies with a remarkable level of resemblance.

Moreover, the complete control over the robot’s movements allowed to identify a passive aerodynamic mechanism helping the robot, and fruit flies, turn during these rapid maneuvers. The research into insect flight is pursued further in the project named “To Be Nimble as a Bee“.

Agility

Apart from fly-inspired rapid banked turns, the robot can perform aerial tricks such as 360-deg flips:

Related publications:

• M. Karásek, F. T. Muijres, C. {De Wagter}, B. D. W. Remes, and G. C. H. E. de Croon, “A tailless aerial robotic flapper reveals that flies use torque coupling in rapid banked turns,” Science, vol. 361, iss. 6407, p. 1089–1094, 2018.
  [Bibtex]

  @article{Karasek2018,
  abstract = {{\textless}p{\textgreater}Insects are among the most agile natural flyers. Hypotheses on their flight control cannot always be validated by experiments with animals or tethered robots. To this end, we developed a programmable and agile autonomous free-flying robot controlled through bio-inspired motion changes of its flapping wings. Despite being 55 times the size of a fruit fly, the robot can accurately mimic the rapid escape maneuvers of flies, including a correcting yaw rotation toward the escape heading. Because the robot's yaw control was turned off, we showed that these yaw rotations result from passive, translation-induced aerodynamic coupling between the yaw torque and the roll and pitch torques produced throughout the maneuver. The robot enables new methods for studying animal flight, and its flight characteristics allow for real-world flight missions.{\textless}/p{\textgreater}},
  author = {Kar{\'{a}}sek, Mat{\v{e}}j and Muijres, Florian T. and {De Wagter}, Christophe and Remes, Bart D. W. and de Croon, Guido C. H. E.},
  doi = {10.1126/science.aat0350},
  issn = {0036-8075},
  journal = {Science},
  month = {sep},
  number = {6407},
  pages = {1089--1094},
  publisher = {American Association for the Advancement of Science},
  title = {{A tailless aerial robotic flapper reveals that flies use torque coupling in rapid banked turns}},
  url = {http://www.sciencemag.org/lookup/doi/10.1126/science.aat0350},
  volume = {361},
  year = {2018}
  }