Design and Flight Testing of a Convertible Quadcopter for Maximum Flight Speed

摘要

Quadcopters are currently experiencing a resurgence made possible with low cost access to commercial off-the-shelf (COTS) electronics and lightweight, high-discharge rate, high capacity lithium batteries driving ever-more efficient electric motors. The use of multiple differential motors at the small scales ideal for remote control flight, makes flying a helicopter approachable to the uninitiated due to the automatic feedback control provided by onboard sensors. But in the more than 100 years since the quadcopter's inception, the problem of achieving high speed has never been solved. This project's goal was to revive an alternative method with clear advantages in the unmanned aerial vehicle (UAV) world: the "tailsitters," combined with the modern capabilities of the quadcopter architecture to unlock the hidden top speed of these aircraft. The patented XQ-139 aircraft that resulted, lifts itself vertically using four independent rotors driven by electric motors and remote controlled with augmented stability. Unlike conventional quadrotors, it pitches over to horizontal "missile mode" flight using four fixed wings and a cross-tail to provide lift and flight control. In this way, the onboard power necessary to hover is fully available to drive the aircraft's top speed. Included is a thorough discussion of the theory, this new aircraft's design features, the tradeoffs involved, its stability, and the resulting performance characteristics based on static testing and flight test data. The potential applications of the vehicle specific to its transitioning capability in private consumer, commercial, industrial, government, and military applications conclude the paper.