Vanderbilt engineers build robotic 'bugs' that can go the distance

April 30, 2000

Mechanical engineers at Vanderbilt University have designed and constructed a small robotic "bug" that can scuttle more than half a mile on a single battery charge.

The leader of the project, Michael Goldfarb, reported on the development of what may be the smallest-sized robot capable of traveling significant distances at a special workshop on mobile micro-robots being held on Friday, April 28 at the IEEE Conference on Robotics and Automation in San Francisco.

"We set out to determine just how small we can make viable robotic technology, and we've done that," says Goldfarb, an assistant professor in mechanical engineering.

Although they started out with even tinier versions, the smallest practical robot that the researchers could produce turned out to be about the size of one of those giant rhinoceros beetles found in the tropics. It is about three inches long and weighs about two ounces.

The two-and-a-half year program to develop the robotic bugs is part of a larger program funded by the Defense Advanced Research Projects Agency (DARPA) that is exploring the use of mobile micro-robots for military reconnaissance and intelligence gathering. The basic idea is that soldiers could carry large numbers of these lightweight, mechanical scouts and use them to investigate the terrain ahead, detecting enemy troops, minefields and other hazards.

The Vanderbilt design was one of three micro-propulsion systems developed as part of the program. Researchers at Los Alamos National Laboratory developed small robots using batteries and electric motors. A team at Sandia National Laboratory built a robotic hopper powered by gasoline. But the other two micro-robots measure between 10 to 12 inches in length and are substantially larger than Vanderbilt's.

To achieve a minimum size, Goldfarb and Ephrahim Garcia, a professor of mechanical engineering who took a leave of absence from Vanderbilt more than a year ago to work at DARPA, took a different approach. They decided to combine batteries with an unusual material called piezoelectric ceramic (PZT) that physically expands when an electrical voltage is applied to it.

For locomotion at this scale PZT had a number of potential advantages, the researchers figured. "It can be made in one piece," says Goldfarb. "There are no significant lower limits to the size of the actuators that you can make. They are also very energetically conservative: They don't throw away a lot of energy, so most of the electrical energy comes out as mechanical energy." In this respect PZT is 90 percent efficient, compared to about 60 percent for DC electric motors.

"Two-and-a-half years ago, when we began this project, we did not know whether this alternative design paradigm would work," he says. In fact, Goldfarb and his research team, which consists of research engineers Mike Gogola and Dan Monopoli plus four graduate and undergraduate students, went through more than 10 prototypes before achieving an optimal design. One of their major challenges was creating a mechanism that would travel at a reasonable speed. "The first few designs that we came up with had maximum speeds of about a millimeter per second, about one three-hundredths of what we can do now," Goldfarb says.

Their final design can cover about a foot per second and carry a one-ounce payload. That allows it to tote a battery that can keep it running for 45 minutes, long enough to cover about a half mile. The lightest chip video cameras available commercially weigh about half an ounce, so the insectile robot is perfectly capable of carrying one, although the researchers haven't done so.

With a second DARPA grant, the Vanderbilt researchers have been attempting to apply this same approach to create flying robotic bugs, micro-ornithopters that fly by flapping their wings. But here the engineers may have run into a fundamental obstacle. PZT ceramics are highly efficient but they are also relatively heavy. The critical factor in mechanical flyers is not energy efficiency, but energy density-the amount of energy that a device can develop per ounce.

Goldfarb's group has designed and tested a number of different micro-ornithopters. But so far none of them has been able to lift its own weight. For the last few months, the researchers have been doing experiments to determine exactly how much power PZT actuators can deliver and to see if there are any tricks they can use to make them deliver more. So far, none the tricks they've tried have worked.

While the Vanderbilt group has concentrated on the issue of locomotion, other research groups are looking at controllers that allow them to navigate and give them some degree of artificial intelligence. Still others are exploring different kinds of payloads that they could carry-such as motion sensors, video cameras, microphones and other sensor-packs to detect land mines, toxic gases and biological weapons.

Proponents point out that robotic creepy-crawlers of this sort might also find a number of non-military applications in law enforcement, security, and inspection of pipes, ducts and other inaccessible or hazardous areas.
For more info:

Vanderbilt Center for Intelligent Mechatronics:

DARPA's Microsystems Technology Office Distributed Robotics program:

Prof. Michael Goldfarb's home page

Vanderbilt Register article on project (Dec 1997)

Vanderbilt University

Related Energy Articles from Brightsurf:

Energy System 2050: solutions for the energy transition
To contribute to global climate protection, Germany has to rapidly and comprehensively minimize the use of fossil energy sources and to transform the energy system accordingly.

Cellular energy audit reveals energy producers and consumers
Researchers at Gladstone Institutes have performed a massive and detailed cellular energy audit; they analyzed every gene in the human genome to identify those that drive energy production or energy consumption.

First measurement of electron energy distributions, could enable sustainable energy technologies
To answer a question crucial to technologies such as energy conversion, a team of researchers at the University of Michigan, Purdue University and the University of Liverpool in the UK have figured out a way to measure how many 'hot charge carriers' -- for example, electrons with extra energy -- are present in a metal nanostructure.

Mandatory building energy audits alone do not overcome barriers to energy efficiency
A pioneering law may be insufficient to incentivize significant energy use reductions in residential and office buildings, a new study finds.

Scientists: Estonia has the most energy efficient new nearly zero energy buildings
A recent study carried out by an international group of building scientists showed that Estonia is among the countries with the most energy efficient buildings in Europe.

Mapping the energy transport mechanism of chalcogenide perovskite for solar energy use
Researchers from Lehigh University have, for the first time, revealed first-hand knowledge about the fundamental energy carrier properties of chalcogenide perovskite CaZrSe3, important for potential solar energy use.

Harvesting energy from walking human body Lightweight smart materials-based energy harvester develop
A research team led by Professor Wei-Hsin Liao from the Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong (CUHK) has developed a lightweight smart materials-based energy harvester for scavenging energy from human motion, generating inexhaustible and sustainable power supply just from walking.

How much energy do we really need?
Two fundamental goals of humanity are to eradicate poverty and reduce climate change, and it is critical that the world knows whether achieving these goals will involve trade-offs.

New discipline proposed: Macro-energy systems -- the science of the energy transition
In a perspective published in Joule on Aug. 14, a group of researchers led by Stanford University propose a new academic discipline, 'macro-energy systems,' as the science of the energy transition.

How much energy storage costs must fall to reach renewable energy's full potential
The cost of energy storage will be critical in determining how much renewable energy can contribute to the decarbonization of electricity.

Read More: Energy News and Energy Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to