From Back to the Future hoverboards to Star Wars floating speed bikes, floating vehicles have captured the dreams of nerds for decades. And while anti-gravity remains in the realm of fiction, we’re now getting closer to it being a reality. Palletrone, a flying cart developed by researchers at SeoulTech university is not quite the floating platforms seen in sci-fi movies, ferrying boxes of stuff from some storage room to the Millennium Falcon. But it does offer a glimpse into the wild future of shopping, where a hovering cart can push your shopping bags or Ikea furniture without wheels or tracks.

The Palletrone is a drone-based floating cart, designed to hover and transport goods over any terrain and topography, including carting bags of groceries across a flat supermarket floor and lifting mail and packages up office stairs. It remains level while airborne, even when loaded unevenly, and responds to human input through a simple handle like that of a shopping cart. “It’s a flying cart designed for human-robot interaction-based aerial cargo transportation,” say the researchers behind the prototype, which was recently featured in a study recently published in IEEE Robotics And Automation Letters.

The system uses internal propeller arms equipped with vector rotors. These are capable of generating thrust in different directions, allowing the Palletrone to control itself in the air, hovering, turning, and moving without effort or tipping over at any point. “The Palletrone will try to keep its roll and pitch at zero, to make sure that there’s a flat and stable platform for your preciouses,” according to the research paper.

In its current incarnation, it can theoretically carry loads up to 25 pounds (11.45 kg) with its current propellers but has only been tested with just under 6.5 pounds (2.93 kg) of cargo, barely enough to carry the office mail or some daily groceries. This load capacity is quite modest, but the Palletrone is a proof of concept; an essential step in exploring how drone-based transport could work in real-world settings.

Critical first version

Much of the Palletrone’s success lies in something called its admittance control system. This is basically a set of controls and sensors that adjusts the drone’s response to forces exerted by both the human operator and the cargo itself. Simply put, admittance control means the drone modifies how it moves based on how much force the human exerts on the handle. For instance, if you push the handle forward, the drone moves forward. This system also reacts to the shifting weight of the cargo to ensure smooth movement. And it constantly changes the vector thrust of each of its four engines, much like a Segway constantly moves the wheels to keep its passenger stable.

According to Seung Jae Lee, one of the researchers involved in the project, one of the project’s critical innovations is its ability to distinguish between the weight of the cargo and the force applied by the human operator. According to Lee, they developed a “simple but effective method” to ensure that the drone knows when it’s being guided by a human and when it’s responding to cargo weight shifts. This is crucial for safe operation, preventing the drone from interpreting unintentional weight distribution changes as human input.

To further stabilize its flight, the Palletrone uses a device called Q-filter, an engineering tool that helps smooth out unwanted “motion noise” (which has nothing to do with the actual sound produced by the propeller), or disturbances in the system. In practical terms, it prevents the drone from reacting to tiny, insignificant movements that could make the flight bumpy or unstable. By filtering out this noise the Palletrone can focus on larger, intentional inputs, such as a push from the operator or a significant shift in cargo weight. It’s the Q-filter that makes it possible for the Palletrone to move smoothly, even when carrying irregular loads.

Heir of the Harrier

The Palletrone’s control system is built around eight actuators—four propellers that generate thrust and four servo motors that control the direction of the thrust. Servo motors are small electric motors that can rotate and control parts of a machine with extreme precision. In the case of the Palletrone, the servo motors adjust the angle of the propellers to direct thrust in different directions. This configuration allows the drone to operate with six degrees of freedom, meaning it can independently control both its rotation (tilting or spinning) and its linear movement (up, down, forward, backward) in any direction.

This works very much like two key military airplanes: the iconic Harrier jet and the F-35B, which use vertical takeoff and landing (VTOL) capabilities?. These jets create lift using vectored exhaust to move from a stationary position on the ground into the air, and back again, always keeping themselves leveled and stable. The Palletrone applies a similar principle, using rotors to lift off the ground vertically, then moving in any direction still with the vectoring engines. 

This flying cart can hover in place when left alone, but its flight time is limited by battery life. A docking system is in development to allow one Palletrone to recharge another in mid-flight, offering a potential workaround for this issue.

The Palletrone is a proof-of-concept prototype and still has a lot of challenges ahead before it becomes a product. The drone is not powerful enough to haul heavier loads over long distances, the researchers say. While its hovering capabilities are impressive, the device requires human input for operation. The dream is to have this thing follow you around, carrying your stuff, something the military is also working on to carry injured soldiers or fighting equipment. 

The future

Lee envisions other applications for the Palletrone beyond logistics. “It could serve as a flying tripod or even act as a dolly, allowing for flexible camera movements and angles,” he says. The ability to hover and move precisely could make it valuable in filmmaking and other industries that require mobile platforms for equipment. In spaces where traditional filming tools would be cumbersome or impossible to use, the Palletrone’s agility could offer filmmakers new possibilities for capturing difficult shots, by placing their cameras on top.

For now, the floating cart remains an early-stage prototype with serious limitations in power, noise, and payload. But you have to start somewhere, and the potential for the future is compelling. I love the idea of a levitating shopping cart, yes, but I’m here for the real prize: Marty McFly’s hoverboard.