A prototype lifting-body tilt-rotor drone designed, built, and tested while at Mothership Aeronautics. About 40cm per side and weighs 1.3 kg, all the agility of a quadcopter with high speed forward flight.
LBTR: A New Class of Drone
Multicopters are inherently inefficient at forward flight because they tilt forward, with high drag and downwards lift preventing high speed or long range. A popular solution is the VTOL, great fixed wing performance but not manueverable when hovering. The interceptor is a Lifting Body Tilt Rotor quad with all the agility and function of a multicopter, but capable of long range and high speed flight.
How it Works
The Interceptor uses 2 servo motors to tilt the motor shafts forward or backward in unison, while the body is an airfoil shape with a 2 degree angle of attack. When in forward tilt mode, the body stays level and has massively less drag than a multicopter and even produces lift at high speed. It's also capable of locking the tilt, and flying in standard quadcopter mode.
The Lifting Body
The Airframe is constructed of carbon fiber plate ribs with a 3D printed NylonG leading edge, trailing edge, and skin. This innovative rib and skin method is unique to LBTR where body surface area is desired and the 3D printed components allow all the hardware mounting to be integrated into the physcical airframe. The top surface is 2 layers of NylonG and forms a flexible flap allowing for unprecedented ease of access to the entire drone. The leading edge of the drone contains the FPV camera and cooling fan intake.
The Tilt Rotor
Built around the Px4 Autopilot and Pixhawk flight controller, the Interceptor has a custom mixer written to handle tilting flight. This was developed on a test stand built to test the servo tilt mechanism and mixer controls. All of the gears and the servo mounts are 3D printed Nylon/NylonX and the motor shafts are press fit on two ball bearings each.
The Interceptor sucessfully flew indoors and outside, demonstrating high speed flight with rotor tilt and excellent manueverability in quad mode. The primary design flaw was weight, which limited flight time, however this can be readily resolved as the protoype servo and gear system could be massively shrunk, more batteries could be fit in the body, and the ribs and skin themselves were overbuilt for testing crashes (there were many).