MAVs need to fly in complex terrains under a range of turbulent atmospheric winds. This poses control challenges which even experienced pilots find difficult to cope with. In our previous work we documented the typical turbulent wind environment of MAVs and provided data on spectral density levels, turbulence intensities, length scales and angle-of-attack fluctuations. We also performed initial open-loop flight trials under replicated turbulent conditions in a very large wind tunnel. Sensitivity to disturbance was found to be highly coupled to the MAV configuration. The most benign responses were observed in the rotary wing cases and the most violent in the fixed-wing cases. Here we detail initial flight tests of a fixed-wing aircraft under a variety of constraints designed to limit the degrees-of-freedom to the test craft. Two purpose-designed rigs are described that; 1) permit the craft to perform pure roll, at adjustable angles of attack, and; 2) permit pitch and heave with minimal roll, lateral and fore-and-aft translations. These rigs were used to simplify the tuning of an autopilot system that could include six DOF inertial inputs, pressure sensing (via wing dynamic pressure taps) and strain measurements from spars. The results demonstrated that with no autopilot enabled control was extremely challenging, resulting in some terminal departures. However, relatively steady flight was achieved with a degree of autopilot input via roll rate tracking and damping. A series of relatively small, rapid inputs to the ailerons (at higher frequencies than could be achieved by an experienced human pilot) greatly assisted overall controllability. Furthermore the system demonstrated an ability to hold reasonably straight and level flight in relatively homogenous turbulence (approximately 8% turbulence intensity with 1 m length scale) and when more discreet gusts were generated via upstream bluff bodies.
展开▼
