It’s Like an Airborne Vegas Sphere
Imagine if the Vegas Sphere was a bit smaller and also that it could fly, and you’ve got a pretty good grasp of Erik’s most recent project.
Sphere at the Venetian Resort might just be single-handedly responsible for restoring Las Vegas as the world capital of glitz and glam in the 21st century. People can’t help but stare, which makes Sphere incredibly valuable advertising space. Most cities, however, can’t afford to drop billions of dollars on such a project and most advertisers can’t to rent the space. But it isn’t necessary to bring people to a giant sphere if you can bring a small sphere to people instead. That’s why Erik put a persistence of vision display on a drone to create an airborne sphere.
This is a drone carrying a large persistence of vision (PoV) display, which is a ring-shaped strip of RGB LEDs spinning fast enough to trick human eyes into seeing a solid spherical screen. Such displays normally rest on shelves and transitioning to the air presented a serious challenge: physics.
As you hopefully learned in school, every action has an equal and opposite reaction. So, spinning the ring of LEDs produces torque that causes the entire drone to spin. That exact problem is why helicopters have tail rotors to counteract the torque of the main rotors and keep the fuselage stable. In this case, Erik’s solution was to add something akin to a tail rotor to push in the opposite direction as the spinning PoV display.
To do that, Erik first had to determine how much force the PoV display was exerting. He then measured the force of a pair of drone motors with rotors to see if they could exceed that. They couldn’t, so he increased the size of the rotors until they could. He then mounted those inside the “sphere” of the PoV display, oriented so they’re counteracting its rotation.
Despite using lightweight components and frame parts, the drone was getting pretty heavy and so Erik used a total of eight motors to provide lift. He doesn’t give any detail about the flight controller or algorithms involved, but they must be fairly sophisticated for the “tail rotors” to respond in real-time with the exact amount of force necessary to counteract spinning — but not so much that they end up causing the drone to spin the opposite direction.
Whatever control magic Erik invoked, it worked. The drone is able to fly while spinning the PoV display up to full speed, so it can show full-color imagery just like Vegas’s Sphere.