Caltech’s LEO Flying Biped Can Skateboard and Slackline



Again in February of 2019, we wrote a few form of humanoid robotic factor (?) beneath improvement at Caltech, known as Leonardo. LEO combines light-weight bipedal legs with torso-mounted thrusters highly effective sufficient to elevate the complete robotic off the bottom, which might handily deal with on-ground dynamic balancing whereas additionally enabling some slick aerial maneuvers.

In a paper printed right this moment in Science Robotics, the Caltech researchers get us caught up on what they have been doing with LEO for the previous a number of years, and it may now skateboard, slackline, and make dainty airborne hops with exceptionally elegant landings.


These heels! Looks like an actual sponsorship alternative, proper?

The model of LEO you see right here is considerably totally different from the model we first met two years in the past. Most significantly, whereas “Leonardo” used to face for “LEg ON Aerial Robotic DrOne,” it now stands for “LEgs ONboARD drOne,” which often is the first even reasonably profitable re-backronym I’ve ever seen. In any other case, the robotic has been fully redesigned, with the model you see right here sharing zero components in {hardware} or software program with the 2019 model. We’re informed that the previous robotic, and I am quoting from the researchers right here, “sadly by no means labored,” within the sense that it was rather more restricted than the brand new one—the previous design had promise, however it could not actually stroll and the thrusters have been solely helpful for leaping augmentation versus sustained flight.

To allow the brand new LEO to fly, it now has a lot lighter weight legs pushed by light-weight servo motors. The thrusters have been modified from two coaxial propellers to 4 tilted propellers, enabling perspective management in all instructions. And all the pieces is now onboard, together with computer systems, batteries, and a brand new software program stack. I notably love how LEO lands right into a strolling gait so gently and elegantly. Professor Quickly-Jo Chung from Caltech’s Aerospace Robotics and Management Lab explains how they did it:

Creatures which have greater than two locomotion modes should be taught and grasp correctly change between them. Birds, as an example, endure a fancy but intriguing conduct on the transitional interface of their two locomotion modes of flying and strolling. Equally, the Leonardo robotic makes use of synchronized management of distributed propeller-based thrusters and leg joints to comprehend clean transitions between its flying and strolling modes. Particularly, the LEO robotic follows a clean flying trajectory as much as the touchdown level previous to touchdown. The ahead touchdown velocity is then matched to the chosen strolling pace, and the strolling part is triggered when one foot touches the bottom. After the landing, the robotic continues to stroll by monitoring its strolling trajectory. A state machine is run on-board LEO to permit for these clean transitions, that are detected utilizing contact sensors embedded within the foot.

A black bipedal robot with a round head and four thrusters standing on the ground

It’s extremely cool how Leo neatly solves a few of the most troublesome issues with bipedal robotics, together with dynamic balancing and traversing massive adjustments in peak. And Leo may also do issues that no biped (or human) can do, like truly fly quick distances. As a multimodal hybrid of a bipedal robotic and a drone, although, it is essential to notice that Leo’s design consists of some vital compromises as properly. The robotic must be very light-weight with a view to fly in any respect, which limits how efficient it may be as a biped with out utilizing its thrusters for help. And since a lot of its balancing requires energetic enter from the thrusters, it’s totally inefficient relative to each drones and different bipedal robots.

When strolling on the bottom, LEO (which weighs 2.5kg and is 75cm tall) sucks down 544 watts, of which 445 watts go to the propellers and 99 watts are utilized by the electronics and legs. When flying, LEO’s energy consumption virtually doubles, however it’s clearly a lot sooner—the robotic has a price of transport (a measure of effectivity of self-movement) of 108 when strolling at a pace of 20 cm/s, dropping to fifteen.5 when flying at 3 m/s. Examine this to the price of transport for a median human, which is properly beneath 1, or a typical quadrupedal robotic, which is within the low single digits. Probably the most environment friendly humanoid we have ever seen, SRI’s DURUS, has a price of transport of about 1, whereas the rumor is that the price of transport for a robotic like Atlas is nearer to twenty.

Long run, this low effectivity may very well be an issue for LEO, since its battery life is nice for less than about 100 seconds of flight or 3.5 minutes of strolling. However, explains Quickly-Jo Chung, effectivity hasn’t but been a precedence, and there is extra that may doubtlessly be carried out to enhance LEO’s efficiency, though at all times with some compromises:

The acute balancing capability of LEO comes at the price of constantly working propellers, which ends up in increased vitality consumption than leg-based floor robots. Nevertheless, this stabilization with propellers allowed the usage of low-power leg servo motors and light-weight legs with flexibility, which was a design selection to attenuate the general weight of LEO to enhance its flying efficiency.

There are doable methods to enhance the vitality effectivity by making totally different design tradeoffs. For example, LEO may stroll with the diminished help from the propellers by adopting finite toes for higher stability or increased energy [leg] motors with torque management for joint actuation that may permit for quick and correct sufficient foot place monitoring to stabilize the strolling gait. In such a case, propellers might have to activate solely when the legs fail to take care of stability on the bottom with out having to run constantly. These options would trigger a weight improve and result in the next vitality consumption throughout flight maneuvers, however they’d decrease vitality consumption throughout strolling. Within the case of LEO, we aimed to attain balanced aerial and floor locomotion capabilities, and we opted for light-weight legs. Attaining environment friendly strolling with light-weight legs just like LEO’s continues to be an open problem within the subject of bipedal robots, and it stays to be investigated in future work.

A rendering of a future version of LEO with fancy yellow skins
A rendering of a future model of LEO with fancy yellow skins

At this level in its improvement, the Caltech researchers have been focusing totally on LEO’s mobility techniques, however they hope to get LEO doing helpful stuff out on the planet, and that nearly definitely means giving the robotic autonomy and manipulation capabilities. In the meanwhile, LEO is not notably autonomous, within the sense that it follows predefined paths and would not determine by itself whether or not it must be utilizing strolling or flying to traverse a given impediment. However the researchers are already engaged on methods during which LEO could make these selections autonomously via imaginative and prescient and machine studying.

As for manipulation, Chung tells us that “a brand new model of LEO may very well be appended with light-weight manipulators which have comparable linkage design to its legs and servo motors to develop the vary of duties it may carry out,” with the objective of “enabling a variety of robotic missions which are onerous to perform by the only use of floor or aerial robots.”

Maybe probably the most well-suited purposes for LEO could be those that contain bodily interactions with buildings at a excessive altitude, that are normally harmful for human staff and will use robotic staff. For example, excessive voltage line inspection or monitoring of tall bridges may very well be good purposes for LEO, and LEO has an onboard digital camera that can be utilized for such functions. In such purposes, standard biped robots have difficulties with reaching the location, and customary multi-rotor drones have a difficulty with stabilization in excessive disturbance environments. LEO makes use of the bottom contact to its benefit and, in comparison with a normal multi-rotor, is extra immune to exterior disturbances akin to wind. This might enhance the security of the robotic operation in an outside atmosphere the place LEO can keep contact with a inflexible floor.

It is also tempting to have a look at LEO’s capability to kind of simply bypass so most of the challenges in bipedal robotics and take into consideration methods during which it may very well be helpful in locations the place bipedal robots are likely to wrestle. Nevertheless it’s essential to keep in mind that due to the compromises inherent in its multimodal design, LEO will probably be finest suited to very particular duties that may most immediately leverage what it is notably good at. Excessive voltage line and bridge inspection is an efficient begin, and you may simply think about different inspection duties that require stability mixed with vertical agility. Hopefully, enhancements in effectivity and autonomy will make this doable, though I am nonetheless holding out for what Caltech’s Chung initially promised: “the final word type of demonstration for us will likely be to construct two of those Leonardo robots after which have them play tennis or badminton.”



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