June 25, 1999 "We are trying to imitate biological systems," says Professor Kumar Ramohalli pointing to a 12-inch-long box supported by what look like legs at the front and legs on wheels at the back.
Ramohalli, of the aerospace and mechanical engineering (AME) department at The University of Arizona in Tucson, calls this device BiRoD -- Biomorphic Robot with Distributed power. He hopes to send BiRoDs (pronounced BYE RODS) to Mars and other distant points in the solar system where they will probe, dig, photograph, analyze and generally explore the planets, moons and asteroids.
"BiRoDs are much simpler than robots you have seen in the past," Ramohalli explains.
Look under BiRoD's hood and you'll see it doesn't have gears, servos and other complex mechanical systems. Instead, you find shiny, thin wires and springs known as muscle wires and muscle springs. Hook these wires or springs to a battery and they contract, mechanically mimicking the actions of muscles. They contract because the current flowing through muscle wires causes their molecules to rearrange themselves in a smaller space.
Muscle wires respond in milliseconds or less, can carry 17,000 times their weight and will go through millions of cycles without failing.
Using muscle wires to animate robots has many advantages, Ramohalli notes.
First, getting rid of all those gears, servos and other mechanical parts makes BiRoDs both lighter and much less complex. That means they are less likely to fail and more BiRoDs can be sent in the cargo hold of a spacecraft. For example, 25 BiRoDs would occupy the same space and payload weight that the single Sojourner robot needed on the Mars Pathfinder mission. With more robots, planetary scientists can gather more data, and if one of the robots breaks down, others can take its place.
BiRoDs also are more reliable because they are not as sensitive to dust and other enemies of mechanical systems. "We don't have to provide the kind of protection from the fine, powdery dust found on Mars that is needed by gears and servos," says AME junior Doug Steibich, one of the students who is working on the BiRoD project.
"To me, the most important thing is that power is distributed," Ramohalli adds. "Everything doesn't depend on central control. So if one leg stops working, everything doesn't jam up and freeze. BiRoD can limp along on the other legs."
Currently, the BiRoD prototype has two front legs and two unpowered rear wheels that roll along as the front legs propel it. Soon, however, Ramohalli's BiRoD team plans to replace the rear wheel/leg combination with two more powered legs. This will allow it to walk over obstacles, turn within its own body length, and complete many maneuvers that leave wheeled vehicles in the dust.
The prototype BiRoD also has infrared vision that enables it to avoid obstacles even in complete darkness.
BiRoDs will change the way scientists think about robotic capabilities and how they use them in the field. Unlike most robots, BiRoD can produce bursts of power -- again like a biological systems, less like machines. "You can store energy slowly and expend it suddenly," Ramohalli says. "Cats do this, for instance. They lie around much of the time, but then expend short bursts of energy to catch prey. They eat, store energy, and then are ready for another surge of power. Robots with this kind of capability can hop over an obstacle, turn over a rock or crush a mineral sample. These are things that today's robots can't do."
The BiRoD research is being conducted in the Space Engineering Research Center, which Ramohalli directs. The new technology concept for BiRoD has been filed with NASA. It is protected under a NASA Novel Technology Report.
Related link: http://scorpio.aml.arizona.edu/projects.html
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