Multi-Lifting-Device UAV Autonomous Flight at Any Transition Percentage

Hybrid UAVs with hovering as well as fast forward flight capability or enhanced maneuverability are expected to become increasingly important. To approach the complex problem of autonomous flight in the full flight envelope of these transitioning or reconfiguring vehicles, a simple but powerful approach is presented. A traditional rotorcraft control strategy consisting of an attitude innerloop and position outerloop is enhanced with a lift allocation controller in between. By running several sub-controllers per lift-device, simplicity is kept while allowing sustained flight at any transitioning percentage for any number of lifting devices. The applications of this approach range from hover of fixedwings, or allowing easier fast forward flight of conventional rotorcraft to autonomous flight of most types of hybrid or reconfiguring UAV. Flight test results are presented using the ATMOS hybrid UAV.