Bipedal walking has worked out pretty well for humans. I guess. We’re kind of stuck with it until someone comes up with something better. And the really frustrating part is that all kinds of animals have already come up with better ways of getting around: specifically, birds and insects, who use wings to fly as well as legs and feet to walk. This multimodality makes birds and insects inherently versatile and adaptable, which is why you can find them doing quite well just about everywhere.
Some of the most versatile and adaptable robots also exhibit multimodal characteristics: they can fly and climb, or jump and glide, or even fly and swim. But flying and walking seems to be by far the most useful combination, as evidenced by the variety of animals that can do it, and researchers at the University of Pennsylvania’s GRASP Laboratory have designed a new robot called Picobug that can fly, walk, and even (soon) grab on to stuff.
This lovechild of a quadrotor and a UC Berkeley’s DASH robot displays agility in both terrestrial and aerial operations. The flying bit is straightforward: most of the robot consists of a 22-gram Dragonfly picoquadrotor with a custom autopilot. Underneath is an eight-footed, symmetrical adaptation of DASH, which has the advantage of making sure that the robot is supported by four feet at all times with minimal deformation. The motor that drives these feet can only get them going forwards or backwards, but the Dragonfly’s rotors can yaw the robot to steer it left and right.
In terms of performance, Picobug can fly with a top speed of 6 m/s, and crawl at up to 0.16 m/s on a flat surface. It weighs a total of 30 grams, which is a whole lot of not much: it’s about a third battery, a third motors and props, and the rest is the crawler, frame, and electronics. The big question is, as always, battery life: how much of a difference does the crawling actually make? The simple answer is that the robot uses 10.6 watts while hovering, and 0.6 watt while crawling, resulting in a flight time of 10 minutes and a crawl time of 45 minutes. But since flying is much faster than crawling, the complicated answer involves calculating cost of transport, a dimensionless measurement of how much energy the robot expends to move itself a given distance. The cost of transport while flying works out to be about 36, but just 14 while crawling, meaning that the robot is more than twice as efficient while toddling along on the ground.
It’s important to keep in mind that the whole point of having a multimodal robot, though, is that you can use different modes of locomotion depending on where your robot is and what it’s trying to do: you’re not just restricted to one thing. As the video shows, you can hop into the air to jump over obstacles or rough terrain, while crawling is best for delicate positioning on the ground. And for traveling through tight spaces, using flying and crawling at the same time might be the most effective technique.
The addition of a gripper to the robot (even though it seems to be a bit of a work in progress) is what has the potential to make this robot even more amazing, as the researchers speculate in an upcoming ICRA paper:
The Picobug can easily pick up small objects (on the order of 6mm and 1-2g), although a larger and stronger gripper should enable it to pick up even larger objects. With its multi-modal capabilities, the Picobug can pick up an object while in crawler mode, deliver it to its destination by air, and then return to crawler mode to deposit the object. These capabilities make the flying monkey a powerful tool for object retrieval/delivery and, when coordinated in swarms, for the construction and disassembly of structures.Furthermore, since the gripper is not an integral part of the Picobug’s structure, it can be replaced by mechanisms with other functions, such as a mating device that allows it to couple with another robot or to latch onto a wall or branch.While the three capabilities enabled in the Picobug are sufficient to complete a variety of tasks as listed above, we envision the next generation of such devices to include other abilities, such as cutting /milling/machining, heating/cooling, deposition of glue, etc to facilitate a wider set of applications. Future work must draw from research in swarms as such functionality will only be achieved through the coordination and cooperation between groups of devices with different sets of abilities.
Imagine a huge swarm of these robots, each with a different attachment, all working together to accomplish tasks that no one robot could do by itself. It’s quite a vision, and we like it.
For more details, we spoke with Yash Mulgaonkar, first author on the paper on Picobug and PhD student at GRASP Lab:
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