The Italian Institute of Technology (IIT) has successfully demonstrated the first flight of iRonCub3, marking a milestone in humanoid robot technology. iRonCub3 is the world's first jet-powered humanoid robot designed specifically for operation in real-world environments.

The research team investigated the complex aerodynamics of artificial bodies and developed advanced control models for systems composed of multiple interconnected components. The overall development of iRonCub3, including actual flight testing, took approximately two years. In the latest experiment, the robot was able to lift off the ground by about 50 cm while maintaining stability. This achievement lays the foundation for a new generation of flying robots capable of operating in complex environments while retaining a humanoid structure.

A paper describing the aerodynamics and control research was published in Communications Engineering.

The study was conducted in collaboration with robotics experts from IIT in Genoa, Italy; the team of Alex Zanotti from the DAER Aerodynamics Laboratory at Politecnico di Milano, who conducted a series of comprehensive wind tunnel tests; and the team of Gianluca Iaccarino from Stanford University, who used deep learning algorithms to identify aerodynamic models. This robot flight demonstration represents the latest milestone for the Artificial and Mechanical Intelligence (AMI) Laboratory at IIT in Genoa, led by Daniele Pucci. Their research aims to push the boundaries of multimodal humanoid robots by combining ground mobility with aerial maneuverability, developing robots that can operate in unstructured and extreme environments.

iRonCub3 is a technological upgrade of previous prototypes, based on the latest generation of the iCub humanoid robot (iCub3), designed for remote operation. It integrates four jet engines: two mounted on the arms and two on a jetpack attached to the robot's back.

To support the external engines, the iCub's hardware design required modifications, such as developing a new titanium alloy spine and adding heat-resistant shields. The jet-powered robot weighs about 70kg, with the turbines providing over 1,000N of maximum thrust. This configuration enables the robot to hover and perform controlled flight maneuvers even in the presence of wind disturbances or environmental uncertainties. Exhaust temperatures can reach up to 800°F (approximately 477°C).

"This research is fundamentally different from traditional humanoid robotics, forcing us to make substantial leaps at the technical level," explained Daniele Pucci. "Here, thermodynamics plays a key role—the turbine exhaust gases reach temperatures up to 700°C with flow speeds approaching sonic velocities. Aerodynamics must be evaluated in real time, and the control system must simultaneously handle slow joint actuators and fast jet turbines. Testing these robots is both exciting and dangerous, with no room for improvisation."

The AMI research team focused on the platform's dynamic balance, which is particularly complex due to the robot's humanoid form. Unlike traditional drones with symmetric, compact structures, iRonCub3 has an elongated shape with mass distributed across movable limbs and a variable center of gravity. This required developing advanced flight balance models that account for the robot's multi-body dynamics and the interactions between jet propulsion and limb movements.

Additionally, the movable limbs significantly increase aerodynamic complexity, as every movement of the robot's limbs alters the aerodynamics.

The researchers conducted extensive wind tunnel experiments, advanced computational fluid dynamics (CFD) simulations, and developed AI-based models capable of real-time aerodynamic estimation.

"Our model includes neural networks trained on simulation and experimental data, integrated into the robot's control architecture to ensure flight stability," explained Antonello Paolino, the paper's first author and a PhD student in a joint program between IIT and the University of Naples, who served as a visiting researcher at Stanford for one semester.

Thus, iRonCub3 is equipped with an AI control system that enables it to handle high-speed turbulent airflow, extreme temperatures, and the complex dynamics of multi-body systems during flight.

The advanced aerodynamic models developed by IIT demonstrate that posture and stability can be maintained even during non-stationary maneuvers, such as sequential engine ignition or changes in body geometry.

These studies can be transferred to other robots with unconventional morphologies—a unique situation compared to traditional drones, whose balance relies on symmetry and simplified control strategies that often overlook the robot's own aerodynamics and thermodynamics.

The final design of iRonCub3 is the result of an advanced co-design process specifically for integrating AI and multiphysics into flying robot design. These technologies are innovative in robotics, simultaneously optimizing the robot's morphology and control strategies while considering the complex interactions between aerodynamics, thermodynamics, and multi-body dynamics.

We used co-design to determine the optimal placement of jet turbines to maximize controllability and stability during flight. We also employed advanced design techniques to manage heat dissipation from the engines, ensuring structural integrity even under extreme operating conditions.

The robot underwent a thorough redesign to withstand the harsh conditions associated with aerial maneuvers and introduced major improvements focused on precise actuation, enhanced thrust control through integrated sensors, and advanced planners for coordinated takeoff and landing.

Throughout the design process, we conducted multiple iterative adjustments based on high-fidelity simulations and experimental tests, finalizing the robot's current configuration. This approach allowed the team to overcome limitations of traditional methods, marking a significant step in the automation and integrated design of complex robotic systems.

iRonCub3's first flight test was conducted in IIT's small flight test area, where the robot lifted off the ground by about 50 cm. In the coming months, prototype testing will continue and will be further refined through collaboration with Genoa Airport (Aeroporto di Genova), which will provide a dedicated area set up and equipped by IIT in accordance with all necessary safety regulations. This area will be used for future experimental activities.

It is anticipated that flying humanoid robots like iRonCub3 will be applied in various scenarios in the future, such as search and rescue operations in disaster areas, inspections in hazardous or hard-to-reach environments, and exploration tasks where both manipulation capabilities and aerial maneuverability are crucial.