College of LAS « Illinois

Entomology

The Running of the Roaches

Cockroach research could lead to better robots.

cockroach

Lurking deep within the laboratories of the University of Illinois is a cockroach almost 2 feet long and 8 inches tall.

If this sounds like a nightmare to anyone who has battled 2-inch-long cockroaches in the kitchen, the good news is that this goliath-sized monster is not a living creature. It is a robotic cockroach, a gleaming metallic insect with six legs powered by pneumatic cylinders.

Although the U of I’s robotic cockroach has been idle in recent years, the research on insect walking, which underlies such robots, has not. The work continues in the laboratories of several LAS researchers in entomology, providing vital information to engineers who continue the quest for robots that can walk like insects.

With six legs, robotic insects would have a much easier time working their way through disaster sites and other rugged terrain than either wheeled robots or two-legged robots, explains LAS entomologist Fred Delcomyn. Equipped with cameras, they could also be invaluable exploratory tools in distant environments, such as Mars.

To break down the mechanics of insect walking, Delcomyn’s lab features an elevated, clear plexiglass walkway for roaches, with a camera pointed up from below to take rapid-fire images—roughly 250 images per second. Researchers have used this set-up to study a half-dozen insects, but Delcomyn has focused primarily on cockroaches.

“I picked the American cockroach,” he says, “because it is extremely well-adapted and specialized for high-speed locomotion.”

Most animals, such as dogs or horses, have different gaits—a different sequence of foot placements that depend on the animal’s speed. But insects typically maintain the same gait. It’s called the alternating triangle gait because they alternate three legs at a time. They raise two legs on one side of the body simultaneously with the middle leg on the opposite side, creating a triangular base of support.

“The center of gravity is always within the center of one of the triangles,” Delcomyn says. “This is one reason why insects are so elusive because they can literally turn on a dime.”

Delcomyn’s lab provides a unique opportunity for undergraduate students to perform research as they analyze how cockroaches adapt and change their walking under various situations. For example, what happens when one leg has added weight to it? Or how does the insect adapt when one of the six legs is missing?

“The problems that an animal faces in trying to control its limbs are the same that an engineer faces when developing control for the movement of a robot,” he says.

In addition to aiding engineers, this kind of research offers insights to neuroscientists who are trying to determine how various animals control leg movements. Delcomyn’s lab has shown that when an insect walks slowly, it pays a lot of attention to sensory feedback from the legs. But when moving fast, it “pretty much ignores sensory feedback.”

Understanding how animals use sensory feedback to alter motor output patterns such as walking can help in the development of neural prostheses. These are artificial limbs that use sensory feedback to move more naturally.

Winter 2008