Typically, quadcopter drones need to tilt their front end down when flying forward. This increases their frontal area and drag. An experimental new drone overcomes this limitation by only tilting its rotors.
Developed by a team at the University of California – Berkeley, the aircraft is called QUaRTM, which stands for “QUadcopter with an unactuated Rotor Tilting Mechanism.” It has a rectangular body with four arms, each arm incorporating a rotor/motor module at the end. Instead of being rigidly joined to the main body, the arms are connected to it through spring-loaded hinges.
In this setup, modest amounts of thrust are produced, and the springs hold the rotors horizontally in line with the body. Once a high enough level of thrust is produced, however, the rotor arms overcome the force of the springs, temporarily tilting into the forward flight direction by up to 20 degrees relative to the rest of the drone.
This allows the copter to move forward while keeping its body horizontal, cutting down aerodynamic drag. Also, unlike some other tilt-rotor drones, its tilting mechanism does not require powered actuators – the thrust that’s already being produced by the rotors does all the work.
In outdoor test flights, the QUaRTM drone autonomously flew both with and without its tilting mechanism activated. It was observed that when the mechanism was enabled, the aircraft was able to reach a 12.5% higher top speed, plus it showed better high-speed agility (its maximum “crash-free cruise speed” was 7.5% higher). Its power consumption was over 20% lower in the speed range of 15 to 20 meters (49 to 66 ft) per second.
A paper on the research – which was led by Jerry Tang, Karan P. Jain, and Mark W. Mueller – was recently published in the journal Frontiers.