We aim at developing autonomous miniature hovering flying robots capable of navigating in unstructured GPS-denied environments. A major challenge is the miniaturization of the embedded sensors and processors that allow such platforms to fly by themselves. In this paper, we propose a novel ego-motion estimation algorithm for hovering robots equipped with inertial and optic-flow sensors that runs in real-time on a microcontroller and enables autonomous flight. Unlike many vision-based methods, this algorithm does not rely on feature tracking, structure estimation, additional distance sensors or assumptions about the environment. In this method, we introduce the translational optic-flow direction constraint, which uses the optic-flow direction but not its scale to correct for inertial sensor drift during changes of direction. This solution requires comparatively much simpler electronics and sensors and works in environments of any geometry. Here we describe the implementation and performance of the method on a hovering robot equipped with eight 0.65 g optic-flow sensors, and show that it can be used for closed-loop control of various motions.
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The authors thank the Parc Scientifique office of Logitech at EPFL for providing the bare mouse chips. The authors also thank Przemyslaw Kornatowski for helping designing and manufacturing the flying platform. We also thank Ramon Pericet-Camara, Felix Schill and Julien Lecoeur for their help. We thank Auke Ijspeert for giving us access to some motion capture equipment. Finally, we thank the anonymous reviewers for their contribution in improving the manuscript. The method described in this paper has been submitted for patenting (European patent filing number EP12191669.6). This research was supported by the Swiss National Science Foundation through the National Centre of Competence in Research (NCCR) Robotics.
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Briod, A., Zufferey, JC. & Floreano, D. A method for ego-motion estimation in micro-hovering platforms flying in very cluttered environments. Auton Robot 40, 789–803 (2016). https://doi.org/10.1007/s10514-015-9494-4
- Aerial robotics
- Sensor fusion
- Ego-motion estimation