October 2008 Mechanical Engineering Departments: Tech Focus, Pt. 2

This section was edited by Associate Editor Jeffrey Winters.

Technology Focus part 2:
Instrumentation and Control

Adding Some 'Vroom' to EVs

Forget never having to head to the gas station: One of the best possible benefits of driving an electric vehicle is the quietness of the car. Imagine driving down the highway accompanied only by the sound of the wind whistling by.

But all that silence does come at a potential cost. Engineers at Lotus Cars Ltd. in Norfolk, England, have been working on aspects of the Tesla electric sports car, due to reach the market before the end of the decade. As they have driven around the test site in electric prototypes, the engineers have had some near-misses when people have stepped into the path of the oncoming vehicle.

Spurred by these near-accidents—and by concerns from advocates for the blind, who worry that visually impaired people may be endangered by hybrids and electric vehicles—engineers at Lotus have done something both simple and counterintuitive: They have added the sound of engine rumble to an otherwise quiet car.

“Some people have said that this is a perverse thing to do,” said Colin Peachey, chief engineer at Lotus. “We’ve gone to a lot of trouble to make a quiet electric car. And that’s one of the things people like about electric vehicles. Noise from cars can be seen as noise pollution.”

Electric cars, such as this Tesla prototype, run so quietly that they sneak up on pedestrians.

For many years, of course, automakers have striven to make their cars quieter. Lotus, for one, has developed a noise cancellation technology that actively measures road noise from sensors mounted on the suspension. Combined with data from the engine, the system creates a model of the noises entering the passenger compartment. Using the speakers of the car stereo, an out-of-phase soundwave of that model is piped into the car’s interior, interfering destructively with the environmental noise. The effect cancels out much of the outside noise.

But a completely quiet ride may not be to everyone’s taste. For sports car drivers, the sound of a large engine is part of the attraction. So Lotus also developed synthetic engine noises that can be piped into the interior, providing simulated sounds of, say, a V8 engine.

Beginning earlier this year, that technology has been adapted for use in electric vehicles. Front-mounted speakers will project a narrow beam of typical car noise ahead of the vehicle; visually impaired (or simply inattentive) people can use this sound information to gauge the distance and speed of the oncoming automobile. “A normal car can be heard from about 36 feet away,” Peachey said. “But a hybrid can be heard from only 11 feet.”

Because the sound is directed forward, an electric car using the system will seem noisy only to people in front of it. “Once it’s gone past,” Peachey said, “it sounds as quiet as an ordinary hybrid electric vehicle.”

The system is so simple, Lotus engineers say, that automakers could retrofit it onto existing models. Soon, perhaps, anyone will be able to drive a car that sounds like a Lamborghini, even if it’s really a Prius.

Acid Test

The chemistry of Earth’s oceans is changing: In recent decades, the average level of acidity has increased, a trend that has the potential to endanger many sea animals. Reports in the journal Science suggest that acid from dissolved carbon dioxide is found in upwelling ocean water and that such upwellings could corrode the shells of sea urchins, abalone, and other sea creatures.

To get a better feel for how serious this problem is, marine chemists are investing in a new sensor array designed to monitor the ocean’s pH balance. Sunburst Sensors, a Missoula, Mont.-based technology firm, has developed a device known as the Submersible Autonomous Moored Instrument. The SAMI will hang suspended from buoys in several hundred feet of water. According to University of Montana researcher Mike DeGrandpre, who developed the concept with Sunburst, the sensors will enable marine scientists to monitor pH levels for months at a time, and help them understand both the natural range of variability in acid levels and the processes working to change them.

Sunburst and the University of Montana were awarded a grant from the National Science Foundation, NASA, and the Office of Naval Research in June in conjunction with the SAMI technology. The $980,000 grant is intended to help promote design changes in the ocean monitoring system to make it more available commercially.

Robotic Taster

As any wine snob will tell you, it takes years to train a palate refined enough to fully appreciate the difference between a Château Mouton Rothschild and Two-Buck Chuck. But researchers in Spain and Germany may have found a way to automate the process. Using a six-sensor array, the team has developed a method that not only can tell the difference between a Chardonnay and a Malvasia, but can even identify the vintage.

Artificial tongues have been developed over the past decade, and Anritsu Corp. of Japan has a commercial version that uses potentiometric sensors to discern the five basic tastes: sweetness, saltiness, bitterness, sourness, and umami, which is a taste associated with meat and cheeses. Engineers have held out great hope that such sensors would enable greater quality control in food processing facilities, enabling technicians to “taste” the ingredients or even the final products without introducing subjective human factors.

According to Cecilia Jiménez-Jorquera, an engineer at the Barcelona Institute of Microelectronics, and her colleagues, the wine industry has a great need for a lightweight, automated sensor that can distinguish subtle differences in flavor. Not only could such a device help in the production of wines, but it could help catch frauds trying to pass off inferior varieties as superior vintages.

The researchers used an array of ion-sensitive field-effect transistors incorporated into a single silicon chip. The array was tuned so that it could detect relative levels of substances, such as sodium, potassium, calcium, copper, and silver. Then the team ran analyses of nine samples of four different kinds of wine. Based on the readings from the multisensor array, the researchers were readily able to distinguish among the varieties.

Various wines can be classified based on their principal components, using data from a multi-array sensor chip.

The key, of course, isn’t just the sensor, but the model created from the data of the tested samples. To demonstrate this, the researchers fed in data from a batch of 2004 vintages of various wines; once the distinguishing characteristics of 2004 wines were determined, data from the multisensor array could be used to easily discern any 2004 wine from a 2005 wine.

To be sure, such work could be done by sending wine samples to a laboratory. But the speed and accuracy of the multisensor array opens up all sorts of possibilities for creating hand-held wine-testing devices. Indeed, it’s not so far-fetched to think that in the future, instead of presenting a wine cork for inspection, a sommelier will instead offer the readout from a wine scanner.