UC Davis

This thesis presents a conceptual design for a tilted-airframe unmanned aerial vehicle (UAV) that aims to address the challenge of detecting infected citrus trees by Huanglongbing (HLB) using a remote air sampling method. The tilted-airframe UAV is capable of vertical take-off and landing (VTOL) which can vertically take off and land in an orchard between trees and deploy an extendable boom to collect an air sample for HLB disease detection. The tilted-airframe UAV design is based on a tri-copter airframe with three key modifications: tilted-airframe, a novel moment (yawing and rolling) governing system, and a fixed-wing. When the UAV operates in VTOL mode, the airframe of the UAV is pitched up 45 degrees from the horizontal direction. The tilted-airframe concept simplified the UAV’s mechanism design, with all motors fixed relative to the airframe and the whole airframe tilting during the flight mode transition. Furthermore, the tilted-airframe UAV utilizes a butterfly flap system on each side of the wing to control attitude and allows for constant RPM with fixed-pitch propellers during both hovering and the transition to cruise mode. The addition of a fixed-wing increases flight endurance, range, and cruise performance compared with a conventional multi-copter UAV. However, the tilted-airframe with a fixed-wing brings potential challenge for a stable hovering under wind disturbance and the power efficiency is not as good as a conventional fixed-wing UAV. Overall, this thesis explores the development of a tilted-airframe UAV for air sampling and HLB detection in citrus trees, focusing on the transition from hover to cruise mode, flight motion prediction, data collection, comparison, and cruise performance estimation.