A team of researchers at Seoul National University of Science and Technology (Seoul Tech) has developed an innovative transport drone that operates on multiple flexible rotors, making it capable of self-correcting in flight to remain level.
This new drone, which has been dubbed the “Palletrone,” is designed to carry goods over uneven terrain such as stairs, and it shows promise for a variety of potential applications, including human-transporting flying taxis and drones that can be refueled mid-air.
The prototype features a cargo platform mounted on top of a multi-rotor drone, allowing it to hover steadily while being guided by a person. Using gentle physical interaction, the drone responds to human control as a “flying shopping cart,” an analogy made by the research team. However, while the Palletrone was demonstrated in this form, the researchers say their ambitions extend far beyond simple cargo transport.
The Seoul Tech team, led by Professor Lee Seung-jae from the Department of Mechanical System Design Engineering, recently showcased their hovering platform. In a live demonstration, the drone was equipped with a handlebar, much like the ones found on conventional shopping carts. The system allowed users to load boxes onto the hovering platform, which maintained its balance mid-air, even as it moved up and down stairs. This capability is made possible by the drone’s unique design, which utilizes a center-of-mass estimation algorithm to ensure stability.
As Professor Lee explained, the platform’s main goal is to carry objects across environments where traditional wheeled carts would struggle, particularly on uneven surfaces or stairs. This is achieved through a method the team calls “physical human-robot interaction” (pHRI), which allows the drone to anticipate and respond to human intentions, resulting in a smoother flight experience.
“The drone uses an intuitive interaction technique to predict how the person wants to move,” said Lee. “This results in a seamless human-machine collaboration, even in challenging environments.”
One of the key innovations behind the Palletrone is its ability to maintain horizontal stability without needing to pitch or roll, as traditional drones do when changing direction. This advancement makes it easier to transport sensitive or fragile payloads, as the drone can adjust its path without tilting, which could otherwise disrupt the cargo’s position or damage the items being carried.
“Multi-rotor drones typically bank and roll when they turn or adjust their path, which creates challenges for safely transporting fragile items,” Lee explained. “Our drone, on the other hand, can shift directions while keeping the platform level, minimizing the risk to the cargo.”
The Palletrone has demonstrated its ability to carry objects weighing up to 3 kg (6.6 lbs), but Lee acknowledged that commercial applications at such a low weight limit remain limited. Even though humans could easily carry such loads, the flexibility and stability of the drone are what make it a valuable contribution to cargo transport technologies.
While the Palletrone’s initial design appears to be aimed at assisting with cargo transport over obstacles like stairs, the research team envisions a far broader range of potential applications. As Professor Lee noted, the Palletrone could be used for high-value industries where maintaining horizontal stability is crucial, including:
Medical Supply Delivery: Drones are already being used to transport critical medical supplies, such as blood samples or medications, to remote locations. The Palletrone’s ability to maintain a level flight path could make it a valuable tool for safely delivering delicate medical materials that could be harmed by too much vibration or tilting.
Fragile Payload Transport: From electronics to glassware, the Palletrone’s stability could be leveraged to transport items that are vulnerable to sudden movements or shifts in orientation.
Disaster Relief: The drone could assist in delivering food, water, or medical equipment to areas affected by natural disasters, where uneven terrain or damaged infrastructure would make it difficult to use conventional delivery vehicles.
Additionally, the technology could extend beyond cargo transport entirely. The Seoul Tech team is already exploring the possibility of using the drone’s technology for uncrewed aerial vehicles (UAVs) in urban air mobility solutions, such as flying taxis capable of carrying humans. These UAVs would benefit from the same self-correcting, level-flight characteristics as the Palletrone, offering passengers a smoother and more stable ride.
“The Palletrone can be more than a flying shopping cart,” said Professor Lee. “We see its potential in numerous industries, including urban air mobility and even in military applications where drones could be used to deliver supplies in the field.”
While multi-rotor drones offer excellent control and maneuverability, they are typically constrained by two major factors: speed and range. Unlike fixed-wing drones, which are capable of flying long distances at high speeds, multi-rotor drones—like the Palletrone—are better suited to shorter trips that require precision, such as hovering in place or navigating obstacles.
One of the primary limitations for multi-rotor drones is battery life. The energy demands of hovering, combined with the need to carry a payload, significantly shorten the drone’s flight time. In commercial applications, this is a major challenge, especially for companies looking to use drones for delivery services across longer distances or with heavier payloads.
“Currently, the weight limit is one of the barriers to broader commercial adoption,” Lee admitted. “The drone can carry about 3 kg, which is enough for many smaller tasks, but it’s not sufficient for larger-scale logistics operations.”
One potential solution to this limitation is the idea of mid-air refueling. Lee’s team is researching ways to swap out batteries while the drone remains airborne, allowing it to continue its journey without needing to return to a base station for a fresh charge. This could extend the drone’s operational range and make it feasible for longer deliveries, even in rural or hard-to-reach areas.
Despite the current limitations, the Seoul Tech team’s work is an important step forward in addressing the challenges faced by multi-rotor drones, particularly in achieving greater stability and control during flight. By maintaining a level platform without banking or rolling, the Palletrone opens up new possibilities for using drones in situations where fragile goods or complex environments must be navigated with precision.
For now, the technology is still in the research phase. However, the team’s findings were published in the prestigious IEEE Robotics and Automation Letters, a journal produced by the Institute of Electrical and Electronics Engineers (IEEE), headquartered in New York. This publication places their work at the cutting edge of robotics and automation research, indicating its potential significance for the future of drone-based transport.
As the technology evolves, it’s likely that the Palletrone—or similar drones—will begin to see more widespread use in industries that rely on delicate cargo, humanitarian aid, or even urban transport. And as researchers continue to explore ways to improve battery life, speed, and payload capacity, the future of drone technology looks more exciting than ever.
South Korean researchers at Seoul National University of Science and Technology have developed a groundbreaking drone with flexible rotors that can self-correct mid-flight, offering a stable platform for carrying goods over uneven terrain. Dubbed the Palletrone, this prototype has the potential to revolutionize cargo delivery, particularly in environments where traditional wheeled carts struggle to perform.
Though currently limited by battery life and payload capacity, the drone’s self-leveling technology is a game-changer for transporting fragile goods and promises to have far-reaching implications for the future of drone technology, including human transport and mid-air refueling capabilities.
