Autonomous Flight in Hover and Near-Hover for Thrust-Controlled Unmanned Airships

The ability of airships to fly in hover is a major plus of this category of flying vehicles. However, especially for the case of autonomous flight, this feature can be exploited only recurring to a carefully designed layout of the thrusters on board. Furthermore, the thrusters need to be suitably governed by a dedicated control algorithm. This paper explores a scheme for the control in hover of a thrust-controlled airship without thrust vector control, also assessing its effectiveness in near-hover positioning problems. The control scheme proposed herein extends the capability of a stability augmentation and guidance controller for forward flight, previously introduced by the authors for a conceptually similar airship. A control action based on a system of thrust forces required for hover, and additional thrust components for stabilizing and steering the airship in slow (near-hover) navigation, is thoroughly described. The ensuing control suite is applied and tested in the present paper on the high-fidelity virtual model of a five-thruster airship, showing reasonable stability levels and navigation accuracy of the controlled system.