News | Apr 8, 2019

Army researchers are inventing ways to self-right robotic tanks

Will the Army's robotic tanks be able to self-right if they tip over or flip?

An M2A3 Bradley Fighting Vehicle crew changes position on the range during gunnery training in 2018. The Army is developing a new Next Generation Combat Vehicle as part of a concerted modernization strategy.

Winifred Brown/Army

The U.S. Army is studying how to flip robotic tanks and is making the technology available to industry partners.

In late March, the U.S. Army issued a request for proposals for an Optionally-Manned Fighting Vehicle, a potential replacement for the tracked Bradley Fighting Vehicle.

“Our combat vehicles will have the ability to transition through those disruption zones with lethality and survivability … [and] mobility, to be able to fight the enemy on our terms, and become victorious,” said Brig Gen. Ross Coffman, director of the Next-Generation Combat Vehicle Cross-Functional Team.

While the Army plans to down-select to two prototypes this fall, which it can evaluate and start buying off the shelf, its own researchers have for years been inventing tools and software necessary to keep smaller tracked robots right-side up, with hopes the technological advances will apply to larger robots.

In 2011, Dr. Chad Kessens, a scientist at the U.S. Army Research Laboratory, took a training course with soldiers in which they learned how to use relatively small tracked robots for finding and identifying roadside bombs.

“Through my interactions with the trainers who had actually used robots in Iraq and Afghanistan, I found out that one of the major problems they have is the robots they’re using for this turn over more often than they would like—even once is a problem,” Kessens said in a recent report by the U.S. Army Acquisition Support Center.

One of the soldiers that Kessens worked with said that after 20 minutes of trying and failing to right his robot—which was potentially near an IED—he got out of his vehicle, hustled over to the robot, and rescued it because he valued the robot so much.

And autonomous robots are almost always unable to reorient themselves after falling into a ditch or being knocked over.

So, Kessens developed a two-part software package, referred to as self-righting software, to give the robots that ability. The first part of the software is for analyzing the robot’s structure, while the second part is for planning and executing self-righting maneuvers.

“My job as an Army researcher is to really understand the entire problem,” Kessens said.

His main goal is to understand the robot’s physical structure using the analytical part of the self-righting software— where its joints are and how they are oriented in relation to one another, how heavy the limbs are relative to one another, and all the other different parameters that go into the physical makeup of a robot. The goal of the software is to encompass as many varieties of robotic systems as possible; therefore, the research has to be relatively generic.

However, all research has to start with a set of control parameters: Kessens and the research team assume that the software will be used for robots with rigid bodies, and that have sensors that can determine what configuration the robots are in and in what direction gravity is acting.

“So we need something, a sensor like an IMU—inertial measurement unit—or we could use just accelerometers or inclinometers. There are different ways to get that information,” he said.

An IMU is a common, relatively inexpensive sensor in a smartphone that changes the screen from vertical to horizontal, and vice versa, when the phone is turned sideways—as when you flip your phone to look at a photo, for instance.

The robot used in the team’s research is made of a shoebox-sized blue base, two white, tapered arms on each side, and a red, jointed appendage that carries a counterweight. (All the parts were 3D-printed on the team’s own printer.) It can sense its own orientation and send a signal back to the researcher asking permission to self-right.

However, this robot is just a research platform, said Geoff Slipher, chief of the lab’s Autonomous Systems Division. The research is still in the early stages, and the test robot’s capabilities aren’t what the team envisions for final systems.

“It’s not intended to be anything that the Army would ever intend to field…It allows us to ask and answer research questions. So, our product is not a robotic system; our product is knowledge about how to make robotic systems perform better,” Slipher said.

The research team is also considering the size of the robot in its analysis. Larger robots tend to have more computing power but robots that could fit in the palm of your hand are limited in how much memory they have and how much processing they can do in real time, he said.

“When I talk about having these two pieces [of software], the analysis piece can happen before the robot ever hits the field, and it will generate maps for the robot that can be stored fairly compactly, in terms of memory … but [the robot will] still be able to use [the maps] without requiring a great deal of processing,” Kessens said.

The idea is to use the analytical side of the software to thoroughly assess the robot’s morphology beforehand and then capture that information in a compact form to run as a separate piece of software on the robot that the robot would then use to navigate and self-right. The assessment determines all of the orientations a robot could stably sit in for a given joint configuration on a given ground angle, Kessens said.

The software figures out how those states connect with one another, forming the map—kind of like the way a human remembers how to get up a certain way from a particular starting position, such as lying on your back. “Once you’ve done it, you know how. You don’t have to think about it much because you can access that knowledge,” he said.

The software being developed at ARL can help the Army create its own robotic systems and help the Army purchase commercial systems, Kessens said. Understanding the self-righting abilities of commercial systems gives the Army a reference point for comparing robots, he explained.

The self-righting software is relevant to the development of the Next Generation Combat Vehicle—some of these vehicles will be optionally manned or fully autonomous in the future.

“We can envision a circumstance where those robots are out in a situation far away from help, either human or other robotic partner help, where they would roll over or need to right themselves,” Slipher said. “And so the basic research that Chad [Kessens] is doing is laying the groundwork for a transition path into larger robotic systems so we understand the physics and how the autonomy and the physical substantiation of the robot, how those two things interact, so that when … we actually have a design for a vehicle … then we can understand, OK, here are the requirements that would feed into that in order to build a self-righting capability.”

In 2015, the Army protected some of Kessen’s self-righting invention for small tracked robots in U.S. Patent 8,977,485, titled “Methods for Robotic Self-Righting.”

Now, in cooperation with the Army technology transfer program, TechLink, the Department of Defense’s national partnership intermediary for technology transfer, is helping qualified industry partners take advantage of the research through patent licensing agreements or cooperative research and development agreements.

Through technology transfer, private industry can license and use Army-developed technology in new products sold to military or civilian customers.

Inquiries from interested businesses can be sent to Joan Wu-Singel, a senior technology manager at TechLink, by email at jwu-singel@montana.edu or 406-994-7705.


This story contains reporting from “I’ve fallen and can’t get up,” first published by the Army’s AL&T magazine.