In the effort to enhance robot movements, scientists seem to have taken inspiration from a very unlikely yet common source. Researchers at the Case Western Reserve University Cleveland are studying the movement of cockroaches in an attempt to replicate the roaches’ excellent mobility in irregular ground terrain (through a reflex mechanism), in robots.
The team hopes their research could one day enable robots to engage in more extensive exploration of the planets and more successful search and rescue missions on Earth. Successful replication will also mean better robotic ability in scaling rough terrain during rescue missions.
"Cockroaches are essentially survivalists," said John Bender, a Case Western research associate and lead author of the study. "Our goal is to understand how they're doing it."
What makes the roaches truly unique is their ability to move independently of the brain. Hair-like sensors on the cockroach's back that sense changes in air patterns, a signal that a predator is approaching.
Cockroaches walk by planting three of their legs on the ground for support while manoeuvring the other three feet, said Joseph Kunkel, a biologist at the University of Massachusetts, Amherst. "They actually respond to irregularities in the ground through a reflex mechanism," Kunkel said. "All of this automated movement is controlled through the thorax ganglia."
The thorax ganglia are nerve sensors separate from the brain that detect changes in the amount of stress put on leg joints, Kunkel said. He added that reflex-based movement is commonplace among insects.
"You can take a cockroach, remove the head and it can still walk," said Kevin Rust, an entomologist at the University of California, Riverside. "I show it to my classes all the time."
"They've been around for hundreds of millions of years and that basic body plan hasn't changed much," Rust said. "Obviously, it's been pretty successful."
The cockroach researchers and engineers at Case Western are collaborating to build robotic models of individual legs, as well as full-scale cockroach robots.
This biological reverse-engineering, which Bender called "bio-inspiration," requires a true understanding of how the cockroaches operate.
"You can mimic something without understanding it," Bender said. "But if we build it and it can do all of the same things, then that means we understand it." Bender's study used Central and South American cockroaches, which are bigger and slower than the ones you might find crawling across your kitchen floor. He keeps them in buckets in his lab.
Using high-tech, motion-capture cameras and custom-built software, the team has plotted how the insect's six legs and 26 leg joints work. The hope is to mimic that movement in robots that can or explore other planets.
Bender, used synchronized digital high-speed cameras to produce 3-D images of the leg joints. To enable capturing this movement in detail, Bender's team placed the cockroaches on a slick glass plate and shot high-speed frames of each leg through the glass. In all, the software analysed 106,496 individual 3-D points. Bender’s software helped the team analyse the images in hours instead of weeks.
The study provided the first detailed look at how the cockroach uses its spring-like trochanter-femur joint to distribute its weight as it walks forward.
The joint reduces bouncing as the body's weight shifts forward, then rolls to lift the tibia off the ground as the leg begins its forward swing.
The next step will involve figuring out how cockroaches configure their legs while turning, and segregating brain decisions from instant reflexes in the critters. Depending on the desired motion, cockroaches rotate the legs they use for balance - two on one side of the body and one on the other side."We've figured out forward walking," Bender said. "Now, we want to understand how they're controlling it."
For the next experiment, the cockroaches will be placed on a rotating foam ball in front of three computer screens. The screens will show a small black box that "moves" as the cockroach runs toward it. The team is at least a year from publishing its next study, which aims to shed light on the extent of cockroach brain involvement(I million neurons) in its simple leg reactions.
Once this is successfully replicated in robots, it will hopefully help overcome the mobility barrier robots are up against, as the one faced by the wheel-based NASA rover Spirit, which is stuck in the Martian sand.
The Air Force has funded the leg research at Case, while National Science Foundation grants fund most of the brain research. The team recently was awarded an additional grant from the Defence Advanced Research Projects Agency, an arm of the Department of Defence.
The research is published in the online journal PLoS ONE.