It was shown that an autonomous trajectory generation and autonomous flight along the calculated trajectory is possible for different flight states and scenarios. First possible stationary operating points for autorotation were calculated for the modeled rotorcraft using the blade element theory and the additionally needed power in curves was estimated. Based on these information an existing concept for trajectory generation was adapted for helicopter autorotation flights and integrated into the existing simulation. The simulation was adapted to cope with autorotation flights as well as normal flights. A robust H-infinity controller was developed and a module commanding the velocity controller during trajectory following was implemented. Furthermore a trajectory compliance controller to control the vertical and lateral deviation from the trajectory was included. The calculated stationary operating points showed that steering and thus flying along a trajectory in autorotation is possible. Through variation of the forward velocity or the collective pitch the sink rate can be varied. The results also show that during stationary autorotation the flight of curves does not pose a problem. The trajectories were generated using simple segments, such as straight lines and curves. The path angles of the segments were adapted to the specific flight envelope and wind conditions. The deviations arising due to transitions between these segments can be controlled by the introduced compliance controller. The trajectory generation as well as the adapted controlling and commanding structure were tested with different scenarios. Different topographies, wind conditions and rotor moments of inertia were investigated in this paper. The results show that all the components work robustly for the set tasks. The controller manages to keep the rotorcraft stable during initiation of autorotation as well as during the transitions between the different trajectory segments. The lateral and vertical deviations from the trajectories are controlled by the additional compliance controller and lie within a few meters. The vertical deviation can be controlled by the collective pitch or by adjusting the forward velocity. The collective pitch is the more direct measure but also influence the rotor rotational speed. The controller introduced in this paper mainly works with the collective pitch as control input, but future works should include a blended controlling using the forward velocity as well. The flare only was investigated exemplarily in this contribution. It was shown that a flare maneuver as in theory can be realized with the used controller and that the forward and vertical velocity as well as the pitch can be controlled to zero at one point. Future research in our group will investigate the possible commanding structure for the flare depending on different forward velocities and positions to the landing sites further.


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    Title :

    Autonomous autorotation flights of helicopter UAVs to known landing sites


    Additional title:

    Autonome Flüge mit Autorotation von unbemannten Hubschraubern zu bekannten Landeplätzen


    Contributors:

    Published in:

    Publication date :

    2010


    Size :

    22 Seiten, 59 Bilder, 13 Quellen


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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