Versatile, modular, extensible vtol aerial platform with autonomous flight mode transitions

This paper presents the Quadshot, a novel aerial robotic platform with Vertical Take-Off and Landing (VTOL) capability. Highly dynamic maneuverability is achieved via a combination of differential thrust and aerodynamic surfaces (elevons). The relaxed stability, flying wing, tail-sitter configuration, Radio Controlled (RC) airframe is actively stabilized by onboard controllers in three complementary modes of operation, i.e. hover, horizontal flight and aerobatic flight. In hover mode the vehicle flies laterally, similar to a quadrotor helicopter, can maintain accurate position for aiming payload and land with pinpoint accuracy when equipped with a GPS unit. In horizontal and aerobatic modes it flies like an airplane to cover larger distances more rapidly and efficiently. Dynamic modeling and control algorithms have been discussed before for quadrotors [1]-[4] and classical aircraft configurations, as have other VTOL concepts such as tilt-rotors (eg. the V-22 Osprey) and tail-sitters (eg. the Sydney Univ. T-wing and the Convair XFY-1 Pogo) [5]-[6]. The important contributions of this paper are the combined use of differential thrust in multiple axes and aerodynamic surfaces for flight control, the assisted transition between hover and forward flight control modes with pitch rotation of the entire airframe and the elimination of failure-prone mechanisms for thruster tilting. The development and use of highly extensible Open Source Software and Hardware from the Paparazzi project in a transitioning vehicle is also novel. The vehicle is made highly affordable for both researchers and hobbyists by the use of the Paparazzi Open Source Software [16] and its Lisa embedded avionics suite. Careful attention to the mechanical design promotes large scale manufacturing and easy assembly, further bringing down the cost. The materials selected create a highly durable airframe, which is still inexpensive. Modular airframe design enables quick modification of actuators and electronics, allowing a greater variety of missions. The electronics are also designed to be extensible, supporting the addition of extra sensors and actuators. Custom designed airfoils provide good payload capacity while maintaining 3D aerobatic flight capability; the wing design ensures adequate stability for manual glide control in non-normal situations. This paper covers the software, mechanical and electronic hardware design, control algorithms and aerodynamics associated with this airframe. Experimental flight control results and the design lessons learned are discussed.