External Wrench Estimation, Collision Detection, and Reflex Reaction for Flying Robots

• Published in: IEEE transactions on robotics Vol. 33; no. 6; pp. 1467 - 1482
• Main Authors: Tomic, Teodor, Ott, Christian, Haddadin, Sami
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Collision avoidance; Collision detection; Collision dynamics; Computational geometry; Computer simulation; Convexity; Drones; Electrical impedance; Estimation; flying robots; Hulls; Impedance; Inertial platforms; interaction control; Mobile robots; Obstacle avoidance; reflex reaction; Robot sensing systems; Robots; Robustness; Unknown environments; Weight
• ISSN: 1552-3098; 1941-0468
• DOI: 10.1109/TRO.2017.2750703

Flying in unknown environments may lead to unforeseen collisions, which may cause serious damage to the robot and/or its environment. In this context, fast and robust collision detection combined with safe reaction is, therefore, essential and may be achieved using external wrench information. Also, deliberate physical interaction requires a control loop designed for such a purpose and may require knowledge of the contact wrench. In principle, the external wrench may be measured or estimated. Whereas measurement poses large demands on sensor equipment, additional weight, and overall system robustness, in this paper we present a novel model-based method for external wrench estimation in flying robots. The algorithm is based on the onboard inertial measurement unit and the robot's dynamics model only. We design admittance and impedance controllers that use this estimate for sensitive and robust physical interaction. Furthermore, the performance of several collision detection and reaction schemes is investigated in order to ensure collision safety. The identified collision location and associated normal vector located on the robot's convex hull may then be used for sensorless tactile sensing. Finally, a low-level collision reflex layer is provided for flying robots when obstacle avoidance fails, also under wind influence. Our experimental and simulation results show evidence that the methodologies are easily implemented and effective in practice.