October 2006 Mechanical Engineering Departments: Tech Focus, Pt. 2

This section was written by Associate Editor Jeffrey Winters.

Technology Focus part 2:
Instrumentation and Control

Sky Eye

Back in the go-go days of the 1990s, some bright people had the idea of mounting telecommunications equipment on a blimp and tethering it miles over a city. From such a height, one airship could blanket a large region with cellular telephone or other wireless services.

It takes but a moment's glance at the sky to see that the scheme never made it off the ground. In fact, the antennas needed to send and receive data were too heavy for an economically sized airship to carry aloft. But now engineers in North Carolina have devised a new type of antenna that not only makes airship-based communications or monitoring platforms feasible, but might also find its way into unmanned aerial vehicles or even unmarked police cars.

Researchers in Nevada used a spherical airship (seen in the upper left of the image) to test a new, painted-on communications antenna.

"If you want to be covert, you can use an antenna that's integrated into the vehicle," said Chi Nguyen, an engineer with RTI International, a technology company in Research Triangle Park. "Or by painting an antenna onto a tank, it helps deter an enemy force from disabling the communications system."

Using a conducting polymer first developed by NASA, Nguyen and his colleagues have devised an antenna that is painted onto the skin on their airship. The original polymer, called RP-46, was improved upon by chemists at Unitech, a technology company based in Hampton, Va.

The idea of using this conductive polymer as an antenna is only a couple of years old; indeed, the polymer was developed by Unitech primarily as a shield against electromagnetic radiation. RTI and another Virginia company, Applied EM, were first able to incorporate the polymer into a working receiver just last year.

For a test flight outside of Reno, Nev., in June, the team painted an Iridium antenna on an airship that also carried a standard antenna. Once the craft was aloft, the researchers received GPS signals using each antenna.

"We also made calls to several dignitaries and supporters," Nguyen said. "We basically said, 'Hey, we're using your money wisely. This thing works.' "

The airship group plans to build on this success. Depending on the level of interest, airships using painted-on antennas could be used for tracking illegal migrants crossing the border from Mexico or monitoring tropical weather systems from a position far above the cloud tops. Such a weather-monitoring platform would combine the advantages of spotter planes and satellites, being able to get close to a storm and stay in position for days at a time.

There are uses for the technology beyond surveillance, however. Nguyen said that standard automobiles could use antennas painted on the roof under the exterior coat to pick up the signals from satellite and terrestrial radio and navigation systems. "There's a couple of antennas sticking up there that could be incorporated into the body," Nguyen said.

Hugging the Highway

It may be easy to dismiss newfangled electronic systems on high-end cars as simple sales gimmicks. But a recent study suggests that one new technology now in expensive BMWs and Porsches could prevent as many as 10,000 fatal crashes a year if it were standard in all cars.

Electronic stability control—a system that constantly monitors and reacts to how well the car responds to movements of the steering wheel—is a relatively new technology. It was first offered in 1995 and is standard on less than 40 percent of car models sold in the United States. That means it's only in the last year that enough cars with ESC have been on the road to allow for meaningful statistical comparisons.

Fatal accidents such as this crash in Oregon can be avoided by advanced electronic systems that detect slipping and hydroplaning.

The Insurance Institute for Highway Safety looked at federal and local crash data from 10 states between 2001 and 2004, focusing on the differences in crash rates and fatalities between models with ESC standard and the same models from previous years without it.

Electronic stability control
systems reduced single-car
crashes by 33 percent.

The research found that electronic stability control was found to reduce single-car crashes by 33 percent. For sport utility vehicles, the effect was even greater, cutting such crashes in half. What's more, the reduction in fatalities from single-car crashes was an astonishing 50 to 60 percent.

The way electronic stability control works plays a part in crash reductions. When the ESC's sensors detect that the vehicle is straying from the driver's intended line of travel—due to hydroplaning, say, or slipping on icy roads—the system brakes individual wheels automatically in an attempt to keep the car or truck under control. In some cases, especially those involving excessive speed, the automatic response extends to cutting back on the throttle.

High speeds have been associated with rollovers in SUVs, and that is where ESC really shines. According to the Insurance Institute study, fatalities from single-vehicle rollovers in SUVs equipped with ESC are reduced by 80 percent compared to similar vehicles without the system.

Maximizing Wind

If you're an engineer trying to uncover the most efficient design for wind turbines, there's a lot conspiring against you.

"It's a pretty nasty environment out there," said Jose Zayas, an engineer at the wind technology department of Sandia National Laboratories in Albuquerque, N.M. "The units get struck by lightning, and they're out in the rain and snow 24/7."

That's not the only factor working against data acquisition. Zayas and his Sandia colleagues found that the data was coming in so fast that the information soon filled the recording device, which then had to be switched off and downloaded. This meant that the data series was discontinuous and that it could be collected only when an engineer was on site. Potentially useful readings—especially those from the middle of the night—were unavailable.

To improve on this situation, Zayas and his colleagues, Wesley Johnson, Perry Jones, Dale Berg, and Juan Ortiz, began in 1999 to create a new device that would collect a continuous stream of data on weather conditions, turbine function, and blade performance. Their resulting device, called the Accurate Time Linked Data Acquisition System, would then integrate this flow of sensor readings into a single data stream, compress it, and send the signal to an off-site data recorder. The goal: to provide a rich data set that would enable engineers at Sandia to validate the models used to design advanced wind turbine blades.

The guts of Sandia's ATLAS II wind turbine data acquisition system are housed in a durable, lightning-proof aluminum case.

In a test of the ATLAS II system (the current version is the second generation), the team fitted a 1.5-megawatt, 250-foot-tall turbine with four of the units. The units collected round-the-clock data on 67 separate measurements on both weather conditions and the response of the turbine itself—a GE Energy model in eastern Colorado.

The site was so remote, in fact, that the accumulated data—all 285 gigabytes of it collected over a four-month period ending in early 2005—was transmitted via satellite to the National Renewable Energy Laboratory in Boulder and then relayed to Sandia.

"We created different communication environments—both wireless and hard-wired," Zayas said. "If you're close to a generator, you want to get away from all the electrical noise."

This constant monitoring led to some unique data, Zayas said. At one point, in fact, the turbine tower was hit by lightning, a stress on a turbine that hadn't been recorded before. Fortunately for the ATLAS II, the system had been designed to be quite robust, with both lightning shielding and protection from the elements built in.

Another consideration was cost. The system was built with off-the-shelf components to keep it inexpensive. Even so, Zayas doesn't expect that most turbines will be fitted with such monitors any time soon.

"Wind energy is very cost-driven," Zayas said. "But I think we'll see manufacturers have more on-board data acquisition systems that provide a little more information on the health of the turbines. Maybe not as detailed as the ATLAS system, but I think it's part of the trend."