Caltech gives drones legs: seamless switching between walking and flying, skateboarding, tightrope walking｜Sicence

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This bipedal robot is a little different.

The most eye-catching thing is the slender high heels, and then the propeller thrusters on the arms.

What is this unusual combination for?

First perform a Wuhu takeoff, then land gracefully, transitioning smoothly between walking and flying.

In addition to serving as thrusters for flight, the four propellers are also responsible for controlling the robot's posture in all directions on the ground to maintain balance.

So this robot can hold the recently popular "Slackline" sport , which is similar to tightrope walking.

You can also challenge yourself by going around the slalom on a skateboard.

The robot is nicknamed Leo and its full name is Leonardo. The name is actually a play on words played by the researchers, abbreviated from LEgs ONboARD drOne .

LEO is from California Institute of Technology, and the related paper also appeared on the cover of the latest issue of Science Robotics, a subsidiary of Science.

High voltage line maintenance

In addition to the showmanship in the display effects, the development purpose of LEO is actually aimed at specific application scenarios.

That is, tasks that are difficult for ground robots and drones to complete independently, typical examples of which include high-voltage line maintenance and viaduct inspection.

These tasks are dangerous for humans to perform, as traditional bipedal robots cannot reach them, and drones are not stable enough when facing air disturbances when hovering.

LEO relies on the coordination of his legs and propellers to remain stable as long as he is given a flat surface to stand on, even a slippery surface sprinkled with oil.

Compared with commercial drones, drones will be blown away when the wind comes, but LEO can still stay in place and continue to work.

Increase the wind speed? No problem.

How does LEO achieve such a balance?

Inspired by birds

Soon-Jo Chung, corresponding author of the paper and a professor at Caltech, said the design of LEO was inspired by the way birds move and jump between wires.

What robots need to learn from birds is the correct switching between flying and walking modes .

The LEO robot maintains a smooth trajectory while flying, and when it reaches the landing point, it adjusts its flying speed to the same walking speed after landing.

This way, after one foot lands and switches to walking mode, you can continue walking smoothly at the same speed.

These controls are accomplished by the state machine circuits on the robot and the sensors on its feet.

In addition, in order to fly, it must be lightweight. The main part of LEO is made of carbon fiber . It is 0.75 meters tall and weighs only 2.58 kilograms.

The integrated DC brushless motor controls the movement of the legs and is installed close to the waist to reduce the inertia of the legs.

The toe part is made of hemispherical polyurethane rubber, which has a high friction coefficient and can prevent slipping.

High heels are also designed to minimize area and weight while maintaining stability when standing still.

There are four tilted propeller thrusters on the arms, which can bear part of the weight of the fuselage through thrust when not flying, and can control the robot's posture in any direction.

This lightweight design also comes at a price, such as low walking efficiency .

Of the total 544 watts of power used when walking, 445 watts are used to control the propeller thrusters for balance, while the legs and other electronic devices consume only 99 watts in total.

If we use the CoT (Cost of Transportation) indicator to measure the energy consumption during movement , the CoT value of LEO when walking at a speed of 20 cm per second is 10 8, and the CoT value can be reduced to 15 when flying at a speed of 3 meters per second .

In comparison, the CoT value of bioenergy used by humans is far less than 1, and the CoT value of Boston Dynamics' bipedal robot when walking is around 20.

Currently, the battery on LEO can only sustain it for 100 seconds of flight or 3.5 minutes of walking.

In response, the researchers explained that efficiency optimization is not the highest priority task at present , and they plan to implement all the necessary functions first before considering it.

To actually get the job done, it is also necessary to expand LEO's short propeller arms into real arms, and use visual algorithms and machine learning to increase the robot's autonomy.

The researchers plan to build two LEO robots for their next demonstration and have them play badminton and tennis against each other.

It would be exciting to imagine a robot like this flying up and spiking the ball.

Paper address:
https://www.science.org/doi/10.1126/scirobotics.abf8136

Demo video:
https://www.youtube.com/watch?v=h3bkvVXsVFM

References:
[1] https://spectrum.ieee.org/bipedal-drone-robot-caltech
[2] https://www.caltech.edu/about/news/leonardo-the-bipedal-robot-can-ride-a-skateboard-and-walk-a-slackline