agile like a helicopter - efficient like a plane - unique like a ufo
Classic rotorcrafts, such as helicopters, work due to complex mechanics and especially
the interaction between the main and the tail rotor. Small and light microcontrollers are
widely available today. Using them, concepts for rotorcrafts normally uncontrollable by
human pilots alone can finally be mastered. This can be achieved by combining aerodynamics and modern hard- and software. In my project I evaluated how to design and
build such a not yet documented and unconventional flying object from scratch.
The roflCopter is a rotorcraft working like a helicopter’s main rotor taken as a single
flying object on its own. This leads to a continuously spinning flying disk and therefore
several challenges in designing, building and especially controlling the copter and its electronics.
To spin, two motors with propellers installed at the end of a rod mounted perpendicular to two rotorblades drive the rotor up to 850rpm in average. Two servo motors
tilt the rotorblades to change the angle of attack during flight and thereby altering the
lift respectively. Aileron-like flaps at each rotorblade tip are pulled down by actuators in
2-3ms. They alter the lift force of each rotorblade to tilt the whole copter and make it
steerable in any direction.
The final goal is to build a copter which has the agility of a model helicopter but is
still mechanically simple. It could be used in various applications in which great agility
is needed but other drones would fail. Examples are indoor 3D mapping, cave exploring,
factory inspection or SAR applications.
The idea of rotorcrafts has been around for about 500 years with Leonardo da Vinci
being the first to imagine such an aircraft. While the early designs were based
on complex mechanics only, pilots in today’s rotorcrafts are supported by sensors and
computer systems. In other words, modern aircrafts could also be called "flying computers”. In recent years however, microcontrollers and flight computers have also been built into small model aircrafts. They enable to develop new concepts for flying objects, which have not been buildable by using mechanics only. I tried that with my concept, the roflCopter.
I got the idea to build the roflCopter back in September 2015, started to make the first drafts and build a prototype. The prototype was finished in April 2016 but it was too unable to fly due to various reasons. Despite generating enough lift to fly in theory, the rotor blade mounts were too unstable, the electric components not arranged symmetrically and the whole structure was not aerodynamic enough.
In September 2016 I started building a second prototype based on the insights I got building the first version. This time I didn't started by building the copter but by designing the whole prototype using CAD. By doing that I could manage to fit the design to the technical components and a compact and aerodynamically working model was built. Apart from that I checked which of the components I used in the first version had worked well and which ones I’d need to replace by other, better working components.
The first flight was on February 14th 2017 just four days before the local science fair “Jugend forscht” in Münster, Germany. After winning at the local fair and the science fair on the federal state level, I was awarded the second place in Germany and got the award for the best aerospace project from the German Aerospace Center “DLR” at “Jugend forscht”.
In late 2017 the roflCopter project was nominated by “Jugend forscht” to attend at the Intel International Science and Engineering Fair (Intel ISEF) 2018 where I was honored to win the “Intel ISEF first and best of category award” in “engineering mechanics”.
The working principle of the roflCopter is like the one of a helicopter, but without using a cabin, landing gear, tail rotor and everything else, which makes a helicopter a helicopter. Basically, the roflCopter is a single main rotor that flies. That means that not only the rotor blades are spinning, but instead the whole flying object spins in the air.
In order to spin, the roflCopter has got two brushless motors with two four blade propellers installed at the end of a carbon fiber rod. Lift is not controlled by spinning faster or slower, but instead the rotor blades can be tilted to different angles simultaneously so the roflCopter controls lift in the same way, a helicopter does: by using collective pitch.
However, by simply tilting the rotor blades, the copter cannot be controlled to fly forward, backward, left or right. For doing that the roflCopter has got two control flaps that are installed at each rotor blade tip like ailerons on a plane wing. These flaps can be pulled down for a specific amount of time to give one rotor blade some extra lift compared to the other one. By doing this, the whole flying object can be tilted and controlled in the way, a helicopter is controlled: via cyclic pitch.
Apart from the fact, that this special mode of operation is not realized in conventional aircrafts, it makes use of some of the techniques used in these. For example the concepts of the collective and the cyclic pitch. Furthermore, the roflCopter can detect its orientation to the pilot to know its flight direction. All the movements in flight are finally controlled by special software and algorithms.