Kinematic analysis and control design for a nonplanar multirotor vehicle

A new class of nonplanar multirotor rotary vehicle is introduced that has the capability of independent control of both thrust and torque vectors in three dimensions. The vehicle configuration is based around the use of six thrustproducing rotors arranged in pairs on three separate reference planes. Variable thrust can be provided via fixedpitch/variable-speed rotors or variable-pitch/fixed-speed rotors. The orientation of rotor reference planes affects the orthogonality of force and torque control, and it is shown how maneuverability can be traded with propulsive efficiency. The static mapping between force and torque control outputs and rotor inputs is derived from rotor geometry and a simple rotor aerodynamic model that does not include interference between rotors or fuselage drag and does not explicitly include induced-velocity effects. Controllers are synthesized for both position and attitude control, with acceptable stability demonstrated via Lyapunov analysis. Vehicle closed-loop dynamic response is investigated in simulation, and controller performance is shown to meet design requirements in the presence of unmodeled rotor inertia effects. Experimental results on a static test rig confirm that the simplified rotor aerodynamic modeling used for control synthesis is adequate for symmetric flight conditions around hover. A free flying prototype has been flight-tested in hover, showing that practical vehicles are possible, accepting the fact that increased control capability comes at the expense of reduced payload and duration, compared with a conventional helicopter. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.