Accurate autonomous landing of a fixed-wing unmanned aerial vehicle

[摘要] ENGLISH ABSTRACT: This thesis presents the analysis, design, simulation and practical implementation of acontrol system to achieve an accurate autonomous landing of a fixed-wing unmannedaerial vehicle in the presence of wind gust atmospheric disturbances.Controllers which incorporate the concept of direct-lift control were designed based ona study of the longitudinal dynamics of the UAV constructed as a testbed. Direct-liftcontrol offers the prospect of an improvement in the precision with which aircraft heightand vertical velocity can be controlled by utilising actuators which generate lift directly,instead of the conventional method whereby the moment produced by an actuatorresults in lift being indirectly generated. Two normal specific acceleration controllerswere designed. The first being a conventional moment-based controller, and the seconda direct-lift-augmented controller. The moment-based controller makes use of the aircraft'selevator while the direct-lift augmented controller in addition makes use of theflaps of the aircraft which serve as the direct-lift actuator.Controllers were also designed to regulate the airspeed, altitude, climb rate, and rollangle of the aircraft as well as damp the Dutch roll mode. A guidance controller was implementedto allow for the following of waypoints. A landing procedure and methodologywas developed which includes the circuit and landing approach paths and the concept ofa glide path offset to calibrate the touchdown point of a landing.All controllers and the landing procedure were tested in a hardware-in-the-loop simulationenvironment as well as practically in a series of flight tests. Five fully autonomouslandings were performed, three of these using the conventional NSA controller, and thefinal two the direct-lift-augmented NSA controller.The results obtained during the landing flight tests show that the project goal of a landingwithin five meters along the runway and three meters across the runway was achievedin both normal wind conditions as well as in conditions where wind gusts prevailed. Theflight tests also showed that the direct-lift-augmented NSA controller appears to achievea more accurate landing than the conventional NSA controller, especially in the presenceof greater wind disturbances. The direct-lift augmented NSA controller also exhibitedless pitch angle rotation during landing.

[发布机构] Stellenbosch University