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A Real-Time Game Theoretic Planner for Autonomous Two-Player Drone Racing

Authors: Spica, Riccardo; Falanga, Davide; Cristofalo, Eric; Montijano, Eduardo; Scaramuzza, Davide; Schwager, Mac

 

  • Published in: Proceedings Robotics: Science and Systems 2018
  • Pittsburgh, PA, USA, June 26-30, 2018

To be successful in multi-player drone racing, a player must not only follow the race track in an optimal way, but also compete with other drones through strategic blocking, faking, and opportunistic passing while avoiding collisions. Since unveiling one’s own strategy to the adversaries is not desirable, this requires each player to independently predict the other players’ future actions. Nash equilibria are a powerful tool to model this and similar multi-agent coordination problems in which the absence of communication impedes full coordination between the agents. In this paper, we propose a novel receding horizon planning algorithm that, exploiting sensitivity analysis within an iterated best response computational scheme, can approximate Nash equilibria in real time. We demonstrate that our solution effectively competes against alternative strategies in a large number of drone racing simulations.

Reference

Posted on: January 3, 2019

Fast, Autonomous Flight in GPS-denied and Cluttered Environments

Authors: Mohtam, Kartik; Watterson Michael; Mulgaonkar, Yash; Liu, Sikang; Qu, Chao; Makineni, Anurag; Saulnier, Kelsey; Sun, Ke; Zhu, Alex; Delmerico, Jeffrey; Karydis, Konstantinos; Atanasov, Nikolay; Loianno, Giuseppe; Scaramuzza, Davide; Daniilidis, Kostas; Jose Taylor, Camillo; Kumar; Vijay

 

  • Published in: Journal of Field Robotics

One of the most challenging tasks for a flying robot is to autonomously navigate between target locations quickly and reliably while avoiding obstacles in its path, and with little to no a priori knowledge of the operating environment. This challenge is addressed in the present paper. We describe the system design and software architecture of our proposed solution and showcase how all the distinct components can be integrated to enable smooth robot operation. We provide critical insight on hardware and software component selection and development and present results from extensive experimental testing in real‐world warehouse environments. Experimental testing reveals that our proposed solution can deliver fast and robust aerial robot autonomous navigation in cluttered, GPS‐denied environments.

Reference

Posted on: January 3, 2019

Computing The Forward Reachable Set for a Multirotor Under First-Order Aerodynamic Effects

Authors: Kim, Suseong; Falanga, Davide; Scaramuzza, Davide

 

Collision avoidance plays a crucial role in safe multirotor flight in cluttered environments. Even though a given reference trajectory is designed to be collision free, it might lead to collision due to imperfect tracking caused by external disturbances. In this work, we tackle this problem by computing the forward reachable set (FRS), which is the set of positions and velocities that a multirotor can reach while following a reference trajectory due to tracking errors. Hence, if the FRS is computed before flight, we can utilize it to check the safety of a given trajectory in terms of collision avoidance. To compute a realistic FRS that covers an agile flight envelope, we consider first-order aerodynamic effects, which have the most salient influence on the vehicle. For computing FRS, we conduct a thorough stability analysis including these aerodynamic effects. Then, we present an FRS computation method that can easily be adapted to newly given reference trajectories. The presented method is validated by comparing the FRS with real flight data collected during agile and high-speed flight. In addition, we compare the FRS computed with and without compensating for first-order aerodynamic effect to highlight their significance on the trajectory tracking performance. To the best of our knowledge, this is the first attempt to compute FRSs by incorporating first-order aerodynamic effects for multirotors.

Reference

Posted on: January 3, 2019

Asynchronous, Photometric Feature Tracking using Events and Frames

Authors: Gehrig, Daniel; Rebecq, Henri; Gallego, Guillermo; Scaramuzza, Davide

 

  • Presentet at: European Conference on Computer Vision (ECCV), Munich, 2018

We present a method that leverages the complementarity of event cameras and standard cameras to track visual features with low-latency. Event cameras are novel sensors that output pixel-level brightness changes, called “events”. They offer significant advantages over standard cameras, namely a very high dynamic range, no motion blur, and a latency in the order of microseconds. However, because the same scene pattern can produce different events depending on the motion direction, establishing event correspondences across time is challenging. By contrast, standard cameras provide intensity measurements (frames) that do not depend on motion direction. Our method extracts features on frames and subsequently tracks them asynchronously using events, thereby exploiting the best of both types of data: the frames provide a photometric representation that does not depend on motion direction and the events provide low-latency updates. In contrast to previous works, which are based on heuristics, this is the first principled method that uses raw intensity measurements directly, based on a generative event model within a maximum-likelihood framework. As a result, our method produces feature tracks that are both more accurate (subpixel accuracy) and longer than the state of the art, across a wide variety of scenes.

Reference

    • Date: 2018
Posted on: January 3, 2019

A reconfiguration strategy for modular robots using origami folding

  • Authors: Yao, Meibao; Belke, Christoph H.; Cui, Hutao; Paik, Jamie

  Published in: The International Journal of Robotics Research, 027836491881575 Reconfigurability in versatile systems of modular robots is achieved by changing the morphology of the overall structure as well as by connecting and disconnecting modules. Recurrent connectivity changes can cause misalignment that leads to mechanical failure of the system. This paper presents a new approach …

Posted on: December 7, 2018

A Variable Stiffness Catheter Controlled with an External Magnetic Field

  • Authors: Chautems, Christophe; Tonazzini, Alice; Floreano, Dario; Nelson, Bradley

  Published in: Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) Vancouver, Canada, 2017 Remote magnetic navigation of catheters is a technique used to perform radiofrequency ablation of heart tissue in order to treat cardiac arrhythmias. The flexible magnetic catheters used in this context are in some cases not sufficiently dexterous …

Posted on: November 26, 2018

Optimal Distribution of Active Modules in Modular Robots

  • Authors: Yao, Meibao; Xiao, Xueming; Belke, Christoph H.; Cui, Hutao; Paik, Jamie

  Published in: Journal of Mechanisms and Robotics Reconfigurability in versatile systems of modular robots is achieved by appropriate actuation of their modular units. Optimized distribution of active modules in the modular architecture can significantly reduce cost and energy in the reconfiguration tasks. This paper presents methodology for distribution planning in modular robots that results …

Posted on: November 19, 2018

Differential contributions of subthalamic beta rhythms and 1/f broadband activity to motor symptoms in Parkinson’s disease

  • Authors: Martin, Stephanie; Iturrate, Iñaki; Chavarriaga, Ricardo; Leeb, Robert; Sobolewski, Aleksander; Li, Andrew M.; Zaldivar, Julien; Peciu-Florianu, Iulia; Pralong, Etienne; Castro-Jiménez, Mayte; Benninger, David; Vingerhoets, François; Knight, Robert T.; Bloch, Jocelyne; Millán, José del R.

  Published in: npj Parkinson’s Disease, 4, 1, 32 Excessive beta oscillatory activity in the subthalamic nucleus (STN) is linked to Parkinson’s Disease (PD) motor symptoms. However, previous works have been inconsistent regarding the functional role of beta activity in untreated Parkinsonian states, questioning such role. We hypothesized that this inconsistency is due to the …

Posted on: November 7, 2018

Closed-loop electrical neurostimulation: Challenges and opportunities

  • Authors: Iturrate, Iñaki; Pereira, Michael; Millán, José del R.

  Published in: Current Opinion in Biomedical Engineering, 8, 28-37 Non-invasive and invasive electrical neurostimulation are promising tools to better understand brain function and ultimately treat its malfunction. In current open-loop approaches, a clinician chooses a fixed set of stimulation parameters, informed by observed therapeutic benefits and previous empirical evidence. However, this procedure leads to …

Posted on: November 7, 2018

Probabilistic Terrain Mapping for Mobile Robots With Uncertain Localization

  • Authors: Fankhauser, Peter; Bloesch, Michael; Hutter, Marco

  Published in: IEEE Robotics and Automation Letters, 3, 4, 3019-3026 Mobile robots build on accurate, real-time mapping with onboard range sensors to achieve autonomous navigation over rough terrain. Existing approaches often rely on absolute localization based on tracking of external geometric or visual features. To circumvent the reliability issues of these approaches, we propose …

Posted on: September 21, 2018