Robust hover control of a tailsitter flying machine

[Airicist]

Researchers:

Robin Ritz

Raffaello D'Andrea

[Airicist]

Robust hover control of a tailsitter flying machine

Published on May 29, 2015

This video demonstrates a new algorithm for robust hover control of a tailsitter flying machine. The tailsitter is able to recover from any orientation, including upside down.

A tailsitter (https://en.wikipedia.org/wiki/Tail-sitter) provides hover capability by pointing the nose and thrust direction upwards. For fast forward flight, the vehicle tilts to a near-horizontal orientation, resulting in efficient lift production due to the conventional wing design. Compared to other fixed-wing, hover-capable aircraft such as tiltrotors and tiltwings, the major advantage of a tailsitter is its mechanical simplicity: No mechanism for changing the direction of the propulsion system has to be added, saving weight and increasing reliability.

The algorithm demonstrated in the video is based on Optimal Control. Optimal trajectories for a set of initial orientations are precomputed and the corresponding initial desired body rates are stored in a small lookup table (500 entries). An outer control loop running at 50 Hz reads the desired body rates for the current orientation from the lookup table, and feeds them to an inner control loop. The inner control loop runs at 1000 Hz and tracks the desired body rates with the two propellers and the two flaps using feedback from a rate gyroscope. The resulting real-time computational complexity is extremely low.

The algorithm is presented in research paper "A Global Strategy for Tailsitter Hover Control", submitted to International Symposium on Robotics Research (ISRR), 2015.

* Researchers
Robin Ritz and Raffaello D'Andrea
Institute for Dynamic Systems and Control (IDSC), ETH Zurich, Switzerland - https://idsc.ethz.ch

* Location
ETH Zurich, Flying Machine Arena - https://www.flyingmachinearena.org

* Technical details
Frame: Robbe Mini Wing RC styrofoam airframe
Electronics: Pixhawk PX4 Flight Management Unit
Battery: Thunder Power RC G6 Pro Lite 25C LiPo 350mAh 2S
Motors: Hacker A05-13S
Motor controllers: ZTW Spider 12A ESCs with SimonK firmware
Propellers: 5x3 GWS EP-5030
Flap servos: MKS DS65K
Infrastructure: Flying Machine Arena

* Acknowledgments
This work is supported by and builds upon prior contributions by numerous collaborators in the Flying Machine Arena project. See https://www.flyingmachinearena.org/people .
This research was supported by the Hans-Eggenberger Stiftung and the SNSF (Swiss National Science Foundation).