Caltech and TII Debut X1: A Humanoid-Drone Team for Multimodal Robotics

A New Kind of Robotic Partnership

Researchers at Caltech and the Technology Innovation Institute (TII) in Abu Dhabi have demonstrated a novel robotic system named X1, which combines a bipedal humanoid robot with a multimodal drone that can both fly and drive. The project showcases a "system of systems" approach, where different types of robots collaborate to overcome complex environmental challenges that a single machine could not manage alone.

The demonstration, held on Caltech's campus, featured a modified Unitree G1 humanoid acting as a transport and deployment platform. Strapped to its back was M4, a compact, transforming drone developed at Caltech that can switch between flight and wheeled locomotion. In a simulated emergency scenario, the humanoid navigated through buildings and outdoor spaces before bending over to launch the M4 drone. The M4 then took flight, landed, converted to its driving mode to conserve energy, and later switched back to flight to overcome an obstacle, showcasing a seamless integration of ground and air capabilities.

Combining Strengths for Greater Versatility

The core idea behind X1 is to merge distinct forms of robotic movement—walking, driving, and flying—into a single, coordinated unit. "Right now, robots can fly, robots can drive, and robots can walk," said Aaron Ames, director of Caltech's Center for Autonomous Systems and Technologies (CAST). "But how do we take those different locomotion modalities and put them together into a single package, so we can excel from the benefits of all these while mitigating the downfalls that each of them have?"

This collaborative effort leverages the specialized expertise of several teams. The Ames lab at Caltech focuses on bipedal locomotion, developing control algorithms based on the physics of movement. This allows the humanoid to walk stably on varied terrain, even while carrying a payload like the M4, without relying on pre-recorded human motion data. "The robot learns to walk as the physics dictate," Ames noted.

The M4 transforming drone was developed in the lab of Caltech professor Mory Gharib. For the X1 project, it was upgraded with Saluki, a secure flight controller and computing technology developed by TII, which is designed to provide robust autonomy and protection from cyber threats. TII's team is also leading the development of the system's perception capabilities, using sensors like lidar and cameras to enable the robots to navigate autonomously. A team from Northeastern University, led by Alireza Ramezani, contributed to the morphing design of the M4 robot.

More Than a Tech Demo

While the campus demonstration highlights a potential use case in emergency response, the underlying goal of the collaboration is broader. The teams aim to create foundational technologies for safe, reliable, and trustworthy autonomous systems that can operate in complex, real-world environments.

"In order to have robots all around us, we need these robots to be reliable," said Claudio Tortorici, a director at TII.

The project is still in development. Future work will focus on giving the entire X1 system a higher degree of autonomy, using model-based algorithms and machine learning to allow it to perceive, navigate, and adapt to its surroundings in real time without human intervention. The successful demonstration marks a significant step, but the teams acknowledge that building truly robust and safety-critical systems for widespread use remains a long-term challenge.