Now a group of researchers at Sandia National Laboratories in Albuquerque, N.M., have created a robot vehicle that can do just that. Of course, it's very small. "It's about the size of the last joint on your pinkie," said Doug Adkins, a mechanical engineer at Sandia's Sensor Technologies Department (and a longtime ASME member), part of the team that developed the device. Its constructors think it may be the world's smallest autonomous robot.

The device takes up a mere quarter of a cubic inch and weighs seven grams. The actual dimensions are 0.9-inch long, 0.7-inch high, and 0.5-inch wide, with a roughly triangular profile. It rides on track wheels, like a tiny tank, and can travel about 90 inches in 10 minutes or so and perch itself on a nickel.

The robot carries an 8K ROM processor, a PIC 16C77 from Microchip Inc. of Chandler, Ariz. This controls two Smoovy 3-mm-diameter motors, one for each track, made by RMB SA of Biel-Bienne, Switzerland. The motors are 13 mm long with a 125:1 gear-reduction ratio and are more usually found in such things as cameras and CD players. There is also a sensor for temperature. Three watch batteries, which account for half its weight. provide power to run the thing.

The work began as an effort in Sandia's Intelligent Systems Sensors and Controls Department to produce a Mini Autonomous Robot Vehicle, or MARV. Five years ago, researchers succeeded in producing a robot that contained all the power, sensors, and computing capacity necessary for mobility in a one-cubic-inch package, using commercially available, off-the-shelf parts and conventional machining techniques. But the robot builders wanted it smaller still.

Doug Adkins of Sandia National Labs contemplates a swarm of minirobots.

The solution came from teaming up with the lab's Sensor Technologies Department, whose members were familiar with the challenges of building sensors and other devices on small scales. The first step was to try to shrink the programmable integrated controller, or PIC, that runs the device.

"Eighty percent of these things is packaging," noted Adkins. So the engineers turned to Microchip, which sold the parts without the package. "We just put them on our little glass chip carrier," Adkins said. The carrier was custom-made for the project. A further reduction in size came from Adkins's idea to build the robot's body by stereolithography, a technique where a succession of thin polymer layers are laid down and cured by a laser, producing a strong, lightweight material that can take complex shapes.

Generally thought of as a rapid- prototyping technique, the method proved far quicker and more versatile than machining the parts. "They produced it in a day," Adkins said. "We didn't need the strength of metal. And you can make square holes and battery sockets," another advantage over machining, since, after all, "you can't drill a square hole."

Another idea from Adkins was to replace the robot's wheels, whose small size gave the device only limited mobility, with tiny treads modeled on those used by tanks. "I thought of how tanks with their track wheels can maneuver over many large objects and realized that the mini-robots could benefit from the same type of wheels," he said. With the treads, carpets and even nickels pose no terrors for the little beasties.

"We basically built it around the batteries," Adkins said. "The batteries are the governing limit now." The three 1.5-volt silver oxide batteries let the device operate for 15 minutes.

The operators now must preprogram the robots before sending them out on their missions, telling them where and how far to go. For the rest, they must rely on their sensors. The team would like to add radio communications, allowing a more interactive style of remote control. Chemical sensors, such as ones capable of detecting hydrocarbon compounds, video cameras, and minimicrophones, such as are found in hearing aids, are other possible new wrinkles.

These additions would help equip the little bug-bots for a wide array of possible tasks. They could be released to explore chemical spills, or detect chemical or biological weapons, crawling through pipes or cracks to check otherwise inaccessible areas. Detecting land mines is another possible application, as is military intelligence. And swarms of robots could range though a disaster site looking for human movement or dangerous substances.

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