Researchers have created a remarkable drone that is capable of walking, hopping, and leaping into the air, thanks to its bird-inspired legs. This innovation greatly enhances the types of environments that unmanned aerial vehicles can explore.
EPFL researchers have developed a drone that can walk, hop, and leap into flight using birdlike legs, significantly widening the scope of accessible environments for unmanned aerial vehicles.
The saying “as the crow flies” refers to the most direct path between two locations. However, at EPFL’s School of Engineering, the Laboratory of Intelligent Systems (LIS), led by Dario Floreano, has embraced this concept literally with the creation of RAVEN (Robotic Avian-inspired Vehicle for multiple ENvironments). This unique drone is modeled after perching birds, like ravens and crows, which often transition between flying and walking. Its multifunctional robotic legs enable it to take off in areas where traditional winged drones cannot operate.
“The idea of flight was inspired by birds, and the Wright brothers turned this vision into reality. Yet, current aircraft still fall short compared to what birds can achieve,” explains LIS PhD student Won Dong Shin. “Birds can move from walking to running to flying without needing a runway or a launch pad. Robotics has not yet provided a platform to replicate this kind of movement.”
RAVEN is designed to optimize movement diversity while keeping its weight low. Drawing from the structure of bird legs and extensive observations of campus crows, Shin developed custom, multifunctional bird-like legs for a fixed-wing drone. He employed mathematical modeling, computer simulations, and hands-on testing to find the ideal balance between the complexity of the legs and the drone’s overall weight (0.62 kg). The leg construction secures heavier parts close to the drone’s body, and a mix of springs and motors mimics the strong tendons and muscles found in birds. The lightweight, bird-inspired feet feature two articulated sections that utilize a passive elastic joint, enabling various movements for walking, hopping, and jumping.
“Creating a lightweight robotic system inspired by bird legs and feet came with design, integration, and control challenges that birds have elegantly resolved through evolution,” Floreano mentions. “This project led us to develop the most versatile winged drone thus far and provided insights into the energetic advantages of jumping for take-off in both birds and drones.” The findings have been published in Nature.
Enhanced access for deliveries and emergency support
Previous robots designed for walking were typically too heavy to jump, and those made for jumping lacked suitable feet for walking. The innovative design of RAVEN allows it to walk, navigate uneven terrain, and even jump onto surfaces that are 26 centimeters high. The researchers explored various methods for initiating flight, including taking off while standing and during free fall, discovering that jumping into flight uses kinetic energy (speed) and potential energy (height) most effectively. The LIS team collaborated with Auke Ijspeert from EPFL’s BioRobotics Lab and Monica Daley’s Neuromechanics Lab at the University of California, Irvine, to integrate bird biomechanics into robotic movement.
In addition to shedding light on the pros and cons of powerful legs in birds that commonly switch between flying and walking, these findings suggest a lightweight design for winged drones capable of navigating rough terrains and taking off from cramped spaces without human help. This versatility opens up possibilities for their use in inspections, disaster response, and deliveries in tight locations. The EPFL team is also focusing on refining the design and control of the legs to improve their ability to land in diverse environments.
“Bird wings are akin to front legs in land-based quadrupeds, yet little is known about how birds coordinate their legs and wings — a gap that also exists for drones. These findings mark an initial step towards understanding the design and control mechanisms of versatile flying creatures, and how these insights can be applied to create agile and energy-efficient drones,” Floreano adds.
