Multi-Legged Robot to Replicate Cockroach Locomotion

Cockroaches are commonly looked upon as ugly, unhealthy pests when they invade restaurant kitchens or pantries. Researchers at Johns Hopkins, in the name of science, have put these unwelcome bugs to work.

In a crowded, windowless lab, scholars and students are persuading the bugs to divulge some crucial locomotion tips that could aid future robotic vehicles to navigate treacherous terrain. In the aftermath of an earthquake or on the uncharted, alien surface of another planet, for instance, a cockroach could persist where humans think twice to go.

For missions like these, the Johns Hopkins team wants to construct robots that act more like cockroaches. The team's primary findings are the subject of two interrelated research papers published this month in the journal Bioinspiration & Biomimetics.

Sean W. Gart, a postdoctoral fellow who puts the roaches through their paces, was the chief author of the two papers. The senior author of both papers was Chen Li, an assistant professor of mechanical engineering who directs the Terradynamics Lab. It centers on movement science at the interface of robotics, biology, and physics.

Inside the lab, the cockroaches hurry along tracks containing two types of obstacles: large "bumps" and equally large "gaps." These mimic the barriers and holes the roaches—a Central American species with bodies around two inches long—might come across in their rugged natural habitat, normally a rainforest region tangled with vegetation. The insects contort their torsos, heads, and legs until they discover a way to get themselves across or over the obstacles in order to stay on course.

High-speed cameras capture the roaches' leg and body motions. The videos can later be slowed down to help the researchers understand the precise tactics that small robots might use to overcome the same types of obstacles.

"Where they live, you have all sorts of stuff around you, like dense vegetation or fallen leaves or branches or roots. Wherever they go, they run into these obstacles. We're trying to understand the principles of how they go through such a complex terrain, and we hope to then transfer those principles to advanced robots.

Chen Li, Assistant Professor of Mechanical Engineering​

A few of these roach-inspired improvements are even now being put into action. Li's team built a multi-legged robot to duplicate the insect's running patterns. After meticulously reviewing their bug videos to detect the underlying physics principles, the researchers incorporated a "tail" to help the robots replicate body positions that aided the real roaches to move past the large bumps and gaps on the lab track. This simple modification enlarged the largest gap size that the robot could traverse by 50% and the largest bump size it could traverse by 75%.

"We're just beginning to understand how these critters move through a cluttered 3-D terrain where you have obstacles that are larger than or comparable to the animal or robot's size," says Li, who has been exploring cockroaches since 2012, when he became a UC Berkeley postdoctoral fellow exploring animal locomotion.

The following step will be to establish whether their findings also apply to movement through more haphazardly scattered terrain, such as debris from a demolished building.

Co-authors on the journal article about traversal of large gaps were graduate students Changxin Yan and Ratan Othayoth and undergraduate Zhiyi Ren, all from the Department of Mechanical Engineering.

The study was funded by a Burroughs Wellcome Fund Career Award at the Scientific Interface, a U.S. Army Research Office Young Investigator Award, and Johns Hopkins University's Whiting School of Engineering.

Video credit: LEN TURNER AND DAVE SCHMELICK