Cockroaches gait informs search-and-rescue robot design

detailed picture than just measuring the timing of footfalls — a common metric used today to study gait.

In kinematic phase analysis, the signals are converted into a wave graph that illustrates the insect’s movement pattern. The pattern only changes when the nervous system kicks in. How do the researchers know this? In a separate but similar experiment, they implanted electrodes into the legs of seven cockroaches to measure nerve signals.

The nervous-system delay the researchers observed is substantially longer than scientists expected, Revzen said. And it runs contrary to assumptions in the robotics community, where computers stand in for brains and the machines’ movements are often guided by continuous feedback to that computer from sensors on the robots’ feet.

Revzen said the new findings might imply that the biological brain, at least in cockroaches, adjusts the gait only at whole-step intervals rather than at any point in a step. Periodic, rather than continuous, feedback systems might lead to more stable (not to mention energy-efficient) walking robots — whether they travel on two feet or six.

Robot makers often look to nature for inspiration. As animals move through the world, they have to respond to unexpected disturbances like rocky, uneven ground or damaged limbs. Revzen and his team believe that patterns in how they move as they adjust could give away how their machinery and neurology work together.

The fundamental question is, ‘What can you do with a mechanical suspension versus one that requires electronic feedback?” Revzen said. “The animals obviously have much better mechanical designs than anything we know how to build. But if we could learn how they do it, we might be able to reproduce it.”

The release notes that more than 70 percent of Earth’s land surface is not navigable by wheeled or tracked vehicles, so legged robots could potentially bridge the gap for ground-based operations like search and rescue and defense.

For human gait analysis, Revzen and colleagues said their noninvasive, high-resolution kinematic phase approach could be valuable in the biomedical community.

Falls are a primary cause for deterioration in the elderly,” Revzen said. “Anything we can do to understand gait pathology and stabilization of gait is very valuable.”

These experiments were conducted at the University of California, Berkeley, before Revzen came to U-M. The work was funded by the National Science Foundation (NSF).

— Read more in Shai Revzen et al., “Instantaneous kinematic phase reflects neuromechanical response to lateral perturbations of running cockroaches,” Biological Cybernetics(February 2013)