Flight control system for an autonomous parafoil

[摘要] ENGLISH ABSTRACT: This thesis presents the development of a flight control system (FCS) for an unmanned,unpowered parafoil and the integration with an existing parafoil system in collaboration witha team at the University of Cape Town (UCT). The main goal of the FCS is to autonomouslyguide the parafoil from an arbitrary deployment position to a desired landing target. A nonlinear8 degrees of freedom (8-DOF) parafoil model by C. Redelinghuys is incorporated into aMATLAB Simulink simulation environment. The non-linear model is numerically linearisedand modal decomposition techniques are used to analyse the natural modes of motion. Allmodes are determined to be stable but a poorly damped lateral payload relative twist modeis present which causes large payload yaw oscillations. The FCS is divided into stabilityaugmentation, control and guidance subcomponents. Stability augmentation is proposed inthe form of a yaw rate damper which provides artificial damping for the oscillatory payloadtwist mode. For control, a yaw rate controller is designed with the aim of a fast responsewhile not exciting the payload twist oscillation. Subsequently, an existing guidance methodis implemented for path following. Autonomous path planning and mission control logic iscreated, including an energy management (EM) method to eliminate excess height and aterminal guidance (TG) phase. The TG phase is the final turn before landing and is thelast chance to influence landing accuracy. A TG algorithm is implemented which generatesan optimal final turn and can be replanned en route to compensate for unknown windand other disturbances. The FCS is implemented on existing avionics, integrated with theparafoil system and verified with hardware in the loop (HIL) simulations. Flight tests arepresented but are limited to remote control (RC) tests that verify the integration of theavionics and the parafoil system and test preliminary FCS components.

[发布机构] Stellenbosch University