Science paper on our new DelFly

DelFly Nimble

Science paper on our new DelFly

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We have developed a new, highly agile flapping-wing robot, called the DelFly Nimble. It can mimic high-speed insect escape maneuvers so accurately, that it exhibited very similar motion as fruitflies when performing these same maneuvers.

Interestingly, the robot turned around an axis that was not controlled during the escape maneuver. In particular, it would turn towards the flight direction. A fruit fly does the same, but it was not clear if it did this on purpose or not. Namely, it is not possible to look inside such an insect’s brain during flight. For the robot, however, we know exactly what happens inside its brain. We completely determine its control system and can log all its senses and motor actions during flight.

We found that the turn is due to an aerodynamic mechanism. When flying faster, the moments around the roll and pitch axis of the robot start to become coupled with the yaw axis. We modeled this effect, and the predictions of the model nicely capture the robot and fruitfly data.

The article can be found here: A tailless aerial robotic flapper reveals that flies use torque coupling in rapid banked turns, by Matěj Karásek, Florian T. Muijres, Christophe De Wagter, Bart D. W. Remes, and Guido C. H. E. de Croon, in Science, 14 Sep 2018, Vol. 361, Issue 6407, pp. 1089-1094.


We think that this new robot is an important step towards real-world applications of flapping wing robots. The previous DelFly versions were very sensitive to wind gusts or even strong drafts, such as from a zealous air conditioning system. These older designs had airplane-like tails for steering, which was not sufficient in such situations. Steering with the wings is a solution to this problem.

Given the light weight of flapping wing robots as the DelFly Nimble (weighing 29 grams), they are very safe for flight in indoor spaces and around humans. Applications may include having them fly in greenhouses for monitoring crop or in warehouses for checking stock.

See our press release here.

self-supervised learning of depth estimation

TOP grant on self-supervised learning

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The Dutch Science Foundation (NWO) has granted me a personal grant on the topic of self-supervised learning. The grant, named TOP grant, is intended for researchers who obtained their PhD maximally 10 years ago.

A structured study on self-supervised learning

In the proposal, I forward self-supervised learning (SSL) as a reliable mechanism to have robots learn in their own environment. In SSL, robots have a baseline perception and behavior module, which allows for initial operation. In the same time this module provides supervised targets to a learning process that extends the robot’s capabilities. Where previous work has shown the potential of SSL in isolated case studies, I will now perform – together with the PhD student funded by the project – the first structured study of SSL. The key innovation is the extension of SSL with novel elements and identify and propose solutions to fundamental challenges in the way of its widespread usage.

This image shows a self-supervised learning setup in which a robot with a stereo system uses the stereo-based distance estimates to learn how to estimate distances also with only one camera. After learning, fusion of the distances from the stereo algorithm and the monocular distance estimation lead to more reliable distance estimates. This setup is described in an article that is to be presented at ICRA 2018, in Australia.

In the TOP grant project, we will study fundamental aspects of self-supervised learning, such as the guarantee of a baseline performance and the fusion of baseline and learned perceptual capabilities. If successful, the research will have an impact on many different types of robots, which will be able to significantly improve their perceptual capabilities over time.

Read more on the NWO web site.


First lecture at the world horti center

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Today I gave the first lecture at the World Horti Center (WHC). The WHC is going to be an important international hub for innovations in the horticulture sector. During the lecture, I explained my vision on how swarms of drones will be able to contribute to precision agriculture indoors. Hopefully this is the first step on the way to having drones contribute to important matters such as the reduction of water and pesticide use in horticulture.

First lecture at the world horti center

First lecture at the world horti center

drone learns to see in zero gravity

Drone learns “to see” in zero gravity

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Last few years, I worked together with ESA and MIT on an experiment, in which a drone learns to see in zero gravity. Yesterday, ESA presented our joint work at the International Astronautical Congress in Mexico. In the experiment, the drone started to fly based on stereo vision with two cameras, but learned online to also see distances with a single camera. Already after a few minutes, the drone was able to predict distances with a single camera, which would allow it to keep navigating if one camera broke down. This type of “self-supervised learning” is very promising for future robot exploration in space.

We have also extensively tested the same learning algorithms on a drone on earth (see this article), but on earth it is easier to see distances, since gravity provides a nice reference frame and adds a lot of structure to the environment. In zero gravity, a drone can move in a full 6 degrees of freedom, so it can look at objects in many different ways.

See the news on the ESA page.

First drone day

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Yesterday I went to the first Dutch drone festival to talk about (and demonstrate) small autonomous flying robots. This weekend the festival in Hilv ersum Media Park continues, for instance with FPV drone racing workshops!

Antoni van Leeuwenhoeklezing

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Today I gave a lecture on smart robots at the Delft Science Center, discussing the intelligence of big robots such as self-driving cars and small robots, such as lightweight drones. Great to see such a mix of young and old people interested enough in this topic to sacrifice a sunny Sunday morning for it :)

New theory of seeing distances with one eye

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Today, the journal of Bioinspiration and Biomimetics published my article on seeing distances with one eye.

Please see my web page for more information.

DelFly book published!

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This month, Springer published our DelFly book!

Aerial Robotics symposium in Paris

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Yesterday I gave a keynote speech on tiny autonomous drones at the Aerial Robotics symposium in Paris. The symposium featured some very interesting talks, ranging from how a drone can fly endlessly like an albatross (by exploiting the wind gradient close to the ocean surface) to drones that can eject themselves from the water in a similar manner as flying squids do!

Web site renewed

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Just renewed my web site, making it more accessible and more suitable for viewing on mobile platforms!