Robust control system development forVTOL-to-fixed wing flight transition withthe EcoSoar UAV : A masters thesis in Automatic Control
Abstract: A non switching, non linear, quaternion based attitude P2 controller, together with a sensitivitynormalizing function for the control surfaces has been simulated and implemented on a flying fixedwing with non vectored engines. In simulations the controller worked well in all flight modes,hovering, transition and flying, and also rejected a simple wind disturbance in all modes. Thefirst implementation on hardware did not work due to programming errors causing crashes withunrepairable damages. The second aircraft was built out of a piece of plywood to further simplifythe testing and tolerate more crashes. A flat plate, a flying piece of plywood, is not a proper airfoiland so has no effects due to camber. It is therefore easier to both simulate and tune. The controllerworked acceptable in reality, but does need further tuning. Due to time constraints the weighingof airflow inside and outside the propeller wash could not be fully determined resulting in differentgain in the different flight modes, but initial estimation of the parameters were enough to achieverobust, stable hovering transitioning and flying even in winds stronger than 5m/s.The controllerwas not implemented on an EcoSoar due to time constraints, but the proof of concept flying pieceof plywood proved the controller feasible for future embedding in a modified EcoSoar. A VTOLcapable EcoSoar could be used for critical deliveries in for example the medical field in Malawiwhere suboptimal infrastructure is hindering progress. The need for medical supplies around therural parts of Malawi is great but roads and services are not capable yet. Since a VTOL flyingwing with delivery capabilities can be both cheap to build, and deliver supplies to areas withoutan airfield, it could accelerate development in Malawi and thus greatly increase quality of life forhumans.
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