Researchers at the Singapore University of Technology & Design have achieved a breakthrough in the flight capabilities of drones. They have developed a drone that can change flight modes in mid-air: from vertical to horizontal and vice versa.
New approach
Small drones typically come in two variations: with wings, which are more suitable for flying long distances and carrying heavy payloads and the drones with rotors, which are more agile in take-off but less energy-efficient. There are already several drone makers who have tried to combine these flying techniques in one design, but no one so far took the approach of the makers of the so-called THOR drone.
THOR stands for Transformable HOvering Rotorcraft. THOR achieves very high structural efficiency by using all its aerodynamic surfaces and components in both vertical and horizon flight modes. The drone can transform itself in the air from a flying wing into a kind of spinning bicopter, almost like a spinning 'helicopter seed'. The wings transform into wings while flying.
At first glance, THOR is very similar to monocopters; these use a single rotating blade and a motor that causes the monocopter to soar. THOR builds on that idea by employing two flight modes: hover mode and cruise mode. In hover mode (which the researchers call H-MOD), THOR spins in place with its carrier wings rotating 180 degrees apart, like the rotors of a helicopter. In cruise mode (C-MOD), the hydrofoils align in the same direction and the drone turns into a flying wing. The creators took inspiration for the design from Samara fruit, or winged nut, which makes the same rotational motion to detach from a tree.
Acceptable altitude
"During the transition between C-MOD and H-MOD, we noticed that by putting C-MOD in a climb, the drone was able to maintain an acceptable altitude while the wings switched to the H-MOD configuration. We expect that, given its strong engines, the drone will operate as a bicopter during the transition step, after which the rotary wings will take over as the primary source of lift. In the transition from H-MOD to C-OD, the initiation of an upwind C-MOD was again useful for maintaining a good altitude during the transition. Indeed, the engines were strong enough to immediately take the vehicle out of H-MOD rotation and push it into translational flight."
When the drone is in hover mode, it can rotate its two servo mechanisms sitting in the middle by about 90 degrees to reorient itself for cruise mode. And when it is in cruise mode, it can do the reverse and switch back to hover mode.
Applications
The developers of the THOR drone see many possible applications. "Anything that requires both long range and agile hovering. And because of its inherent potential to scale up, it can be made smaller than other hybrid platforms. That will open up a lot of opportunities as current hybrid UAVs are too big or bulky to operate. You can think of applications like agriculture, surveillance and parcel delivery, all major themes in drone development right now."
Nevertheless, they are still working on improvements, such as of the hardware and software. They are also working on a security element so that eventually the drone can actually start being used. "Safety is an important issue for drones and if we can prove that this system is safe to use in crowded areas, I think the ball will start rolling for further development of this platform."
In case you still can't really imagine how the drone works, the video below might shed some light on it:
By: Kelly Bakker
Source: IEEE/Singapore University of Technology & Design
