Corvus Robotics’ Autonomous Drones Tackle Warehouses

Flying robots can do warehouse inventory way faster than humans

5 min read

Evan Ackerman is IEEE Spectrum’s robotics editor.

Drone flying in a warehouse

Corvus' warehouse inventory tracking system involves autonomous drones that can fly unattended for weeks on end.

Corvus Robotics

Warehouses offer all kinds of opportunities for robots. Semi-structured controlled environments, lots of repetitive tasks, and humans that would almost universally rather be somewhere else. Robots have been doing great at taking over jobs that involve moving stuff from one place to another, but there are all kinds of other things that have to happen to keep warehouses operating efficiently.

Corvus Robotics, a YC-backed startup that's just coming out of stealth, has decided that they want to go after warehouse inventory tracking. That is, making sure that a warehouse knows exactly what's inside of it and where. This is a more complicated task than it seems like it should be, and not just any robot is able to do it. Corvus' solution involves autonomous drones that can fly unattended for weeks on end, collecting inventory data without any human intervention at all.

Many warehouses have a dedicated team of humans whose job is to wander around the warehouse scanning stuff to maintain an up to date list of where everything is, a task which is both very important and very boring. As it turns out, autonomous drones can scan up to ten times faster than humans—Corvus Robotics' drones are able to inventory an entire warehouse on a rolling basis in just a couple days, while it would take a human team weeks to do the same task.

Inventory is a significant opportunity for robotics, and we've seen a bunch of different attempts at doing inventory in places like supermarkets, but warehouses are different. Warehouses can be huge, in every dimension, meaning that the kinds of robots that can make supermarket inventory work just won't cut it in a warehouse environment for the simple reason that they can't see inventory stacked on shelves all the way to the ceiling, which can be over 20m high. And this is why the drone form factor, while novel, actually offers a uniquely useful solution.

It's probably fair to think of a warehouse as a semi-structured environment, with emphasis on the "semi." At the beginning of a deployment, Corvus will generate one map of the operating area that includes both geometric and semantic information. After that, the drones will autonomously update that map with each flight throughout their entire lifetimes. There are walls and ceilings that don't move, along with large shelving units that are mostly stationary, but those things aren't going to do your localization system any favors since they all look the same. And the stuff that does offer some uniqueness, like the items on those shelves, is changing all the time. "That's a huge problem for us," says Mohammed Kabir, Corvus Robotics' CTO. "Being able to do place recognition at the granularity that we need while everything is changing is really hard." If you were looking closely at the video, you may have spotted some fiducials (optical patterns placed in the environment that vision systems find easy to spot), but we're told that the video was shot in Corvus Robotics' development warehouse where those markers are used for ground truth testing.

In real deployments, fiducials (or anything else) isn't necessary. The drone has its charging dock, and the initial map, but otherwise it's doing onboard visual-inertial SLAM (simultaneous localization and mapping), dense volumetric mapping, and motion planning with its 10 camera array and an autonomy stack running on ROS and PX4 for real time flight control. Corvus isn't willing to let us in on all of their secrets, but they did tell us that they incorporate some of the structured components of the environment into their SLAM solution, as well as some things are semi-static—that is, things that are unlikely to change over the duration of a single flight, helping the drone with loop closure.

One of the big parts of being able to do this is the ability to localize in very large, unstructured environments where things are constantly changing without having to rely on external infrastructure. For example, a WiFi connection back to our base station is not guaranteed, so everything needs to run on-board the drone, which is a non-trivial task. It's essentially all of the compute of a self-driving car, compressed into the drone. -Mohammed Kabir

Corvus is able to scan between 200 and 400 pallet positions per hour per drone, inclusive of recharge time. At ground level, this is probably about equivalent in speed to a human (although more sustainable). But as you start looking at inventory higher off the ground, the drone maintains a constant scan rate, while for a human, it gets exponentially harder, involving things like strapping yourself to a forklift. And of course the majority of the items in a high warehouse are not at ground level, because ground level only covers a tier or two of a space that may soar to 20 meters. Overall, Corvus says that they can do inventory up to 10x faster than a human.

With a few exceptions, it's unlikely that most warehouses are going to be able to go human-free in the foreseeable future, meaning that any time you talk about robot autonomy, you also have to talk about safety. "We can operate when no one's around, so our customers often schedule the drones during the third shift when the warehouse is dark," says Mohammed Kabir. "There are also customers who want us to operate around people, which initially terrified us, because interacting with humans can be quite tricky. But over the last couple years, we've built safety systems to be able to deal with that." In addition to the collision avoidance that comes with the 360 degree vision system that the drone uses to navigate, it has a variety of safety-first behaviors all the way up to searching for clear flat spots to land in the event of an emergency. But it sounds like the primary way that Corvus tries to maintain safety is by keeping drones and humans as separate as possible, which may involve process changes for the warehouse, explains Corvus Robotics CEO Jackie Wu. "If you see a drone in an aisle, just don't go in until it's done."

We also asked Wu about what exactly he means when he calls the Corvus Robotics' drone "fully autonomous," because depending on who you ask (and what kind of robot and task you're talking about), full autonomy can mean a lot of different things.

For us, full autonomy means continuous end to end operation with no human in the loop within a certain scenario or environment. Obviously, it's not level five autonomy, because nobody is doing level five, which would take some kind of generalized intelligence that can fly anywhere. But, for level four, for the warehouse interior, the drones fly on scheduled missions, intelligently find objects of interest while avoiding collisions, come back to land, recharge and share that data, all without anybody touching them. And we're able to do this repeatedly, without external localization infrastructure. -Jackie Wu

As tempting as it is, we're not going to get into the weeds here about what exactly constitutes "full autonomy" in the context of drones. Well, okay, maybe we'll get into the weeds a little bit, just to say that being able to repeatedly do a useful task end-to-end without a human in the loop seems close enough to whatever your definition of full autonomy is that it's probably a fair term to apply here. Are there other drones that are arguably more autonomous, in the sense that they require even less structure in the environment? Sure. Are those same drones arguably less autonomous because they don't autonomously recharge? Probably. Corvus Robotics' perspective that the ability to run a drone autonomously for weeks at a time is a more important component of autonomy is perfectly valid considering their use case, but I think we're at the point where "full autonomy" at this level is becoming domain-specific enough to make direct comparisons difficult and maybe not all that useful.

Corvus has just recently come out of stealth, and they're currently working on pilot projects with a handful of Global 2000 companies.

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