Digital hormones for robots

As in a growing child, a flood of hormones will make robots bigger, stronger and more independent. By including hormone-like messaging in a robotic control system, a team at the University of Southern California's Information Science Institute in Marina del Rey has managed to overcome a problem that has been dogging robotics.

Until now, no one has known how to enable a robot to add new parts to itself-a process called "scaling". Robots with this ability could explore deep space independently: shipped to distant planets as a mass of tiny dumb units, they would build themselves into whatever kind of machinery proved appropriate on arrival. One of the advantages of these reconfigurable modular robots would be a high level of "redundancy"-bits could break off without wrecking the whole machine.

Behnam Salemi and his colleagues at the ISI have found a way to make such resourceful robots. These include walking creations that will adapt their gait if you break a leg off, and others that inch along like a caterpillar regardless of what length they have become. Both use software inspired by biological hormones. The team will report on their work at a conference on robotics and automation in Seoul next month.

In nature, hormones trigger events in different parts of the body simultaneously. "For example, when a human experiences sudden fear, a hormone is released by the brain, causing different actions," says Salemi. Fear releases hormones that might make your mouth open and your leg muscles twitch into action. Although the hormone is triggered by the brain, the muscle control is located in the mouth and legs, Salemi says.

Project supervisor Peter Will says: "Hormones are propagated signals that can be modified or delayed-or which can even disappear along the way." This adaptability lets hormones accomplish tasks that a single-destination message could not.

In a segmented or multi-module robot, a message based on digital hormones will reach all connected sections. The hormone message tells all modules about the condition of the others without carrying specific commands. Each module can then interpret this knowledge in its own way.

Each module is an autonomous unit, with its own on-board power supply and motors. The modules connect via simple two-pronged plugs through which the hormones propagate. "You don't even give it information about what gait it should adopt," says Salemi. The human "operator" just tells the robot which direction to move and the robot will figure out the best gait, given its current configuration.

Author: Duncan Graham-Rowe

New Scientist issue: 14th April 2001

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