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Optimal-time quadcopter descent trajectories avoiding the vortex ring and autorotation states

Talaeizadeh, A ; Sharif University of Technology | 2020

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  1. Type of Document: Article
  2. DOI: 10.1016/j.mechatronics.2020.102362
  3. Publisher: Elsevier Ltd , 2020
  4. Abstract:
  5. It is well-known that helicopters descending fast may enter the so-called Vortex Ring State (VRS), a region in the velocity space where the blade's lift differs significantly from regular regions and high amplitude fluctuations are often present. These fluctuations may lead to instability and, therefore, this region is avoided, typically by increasing the horizontal speed. This paper researches this phenomenon in the context of small-scale quadcopters. The region corresponding to the VRS is identified by combining first-principles modeling and wind-tunnel experiments. Moreover, we propose that the so-called Windmill-Brake State (WBS) or autorotation region should also be avoided for quadcopters, which is not necessarily the case for helicopters. A model is proposed for the velocity constraints that the quadcopter must meet in order to avoid these regions. Then, the problem of designing optimal time descent trajectories that avoid the VRS and WBS regions is tackled. Finally, the optimal trajectories are implemented on a quadcopter. The flight tests show that by following the designed trajectories, the quadcopter can descend considerably faster than purely vertical trajectories that also avoid the VRS and WBS. © 2020
  6. Keywords:
  7. Optimal trajectory design ; Quadcopter ; Quadcopter fast descent ; Vortex ring avoidance trajectory ; Vortex ring state ; Windmill brake state ; Rings (components) ; Vortex flow ; Wind tunnels ; Descent trajectories ; First principles models ; High amplitudes ; Optimal trajectories ; Paper research ; Velocity constraints ; Vortex ring state ; Wind tunnel experiment ; Trajectories
  8. Source: Mechatronics ; Volume 68 , 2020
  9. URL: https://www.sciencedirect.com/science/article/pii/S0957415820300428