Sense This

Sensors get smarter and more powerful and learn to share.

They're everywhere. Tiny wireless microelectromechanical sensors—also known as "smart dust" or "motes"—are monitoring temperature, humidity, stress and motion in settings as diverse as crop fields, bridges, factories, warships and the branches of Northern California's mighty redwood trees.

Now, imagine these so-called MEMS implanted in your body, periodically sending joint-load alerts to the orthopedic surgeon who performed your knee or hip replacement. Given extremely rapid advances in the intelligence and flexibility of sensor-based microcontrollers, such "smart implants" aren't all that far-fetched, experts say.

But up until the past year or so, such a scenario was implausible because of limitations in both the power supply and the programmability of most sensors and sensor networks. Sensors normally produce an overwhelming flood of data in a constant stream that steadily depletes their battery power.

With funding from the U.S. Navy, Williston, Vt.-based MicroStrain Inc. is experimenting with piezoelectric materials, which generate electricity as they undergo stress. This way, sensors could collect the power they need from vibrations on a factory floor or from the movement of the person they're implanted in.

Researchers are also fine-tuning software so that sensors deliver summary information, such as alerts or alarms, rather than a steady stream of raw data. This also conserves power.

At Palo Alto Research Center Inc. in California, a team led by principal scientist Feng Zhao is experimenting with an energy-saving "information-driven sensor-querying" algorithm, which would enable sensors to autonomously task themselves to collect and transmit information based on the usefulness of the information.

"It's quite similar to the way humans track information," Zhao says. "You can't pay attention to all stimuli. What we're building is distributed attention for sensor networks. It's the ability to shift and focus attention when new stimuli of interest emerge."

Meanwhile, working with researchers at the University of California, Berkeley, Intel Corp. has created an open-source operating system called TinyOS, which, among other things, enables sensors and sensor networks to report summaries of data or various classifications of information.

"TinyOS renders sensors into programmable routers. You can program what happens close to the sensor and what happens on the network," says David Culler, a Berkeley computer science professor.

This real-time information is then stored in TinyDB, which "can make the physical world like a database," Culler says. "Rather than issue SQL queries to get information out of a database, you issue queries to data streaming from the real world. If you look at the power industry, there's equipment throughout the country that's quite aged, and the ability to watch that equipment would be a huge benefit."

The implications of these advancements for corporate IT departments are huge, Culler adds. "They have to realize there's a new class of computer system emerging, and five years from now, the vast majority of devices in their companies will be these kinds of [sensor-based, networked] devices," he says.

As a result, IT shops will face tough new demands on network bandwidth, data storage and data management.

For example, a typical semiconductor fabrication plant is home to more than 5,000 sensors. "Today, there are electricians who visit the sensors and milk data from them. In very short order, that data will stream in real time," Culler predicts. "That's a whole new kind of IT asset that IT will need to deal with. It allows you to monitor spaces in ways that you couldn't before and to look at interactions between different things."

Remote Control

Increasingly, sensor networks will also be able to share information and be queried and programmed remotely over the Internet to perform certain tasks. This will be possible in large part because of emerging standards developed by Open GIS Consortium Inc., a Wayland, Mass.-based international organization that aims "to make all types of Web-resident sensors, instruments and imaging devices, as well as repositories of sensor data, discoverable, accessible and, where applicable, controllable via the World Wide Web."

"Right now, specific groups in vertical markets develop sensor webs that they know how to communicate with in their own language. All of these webs are independent and can only be used by a particular group," explains Michael Botts, a professor at the University of Alabama in Huntsville and the principal architect of the Sensor Model Language, or SML, a standard XML encoding scheme for metadata that describes sensors and sensor data.

"We're trying to make it easy by setting up standardized [SML] interfaces that would wrap around existing hardware and software," says Carl Reed, executive director of Open GIS's specification program.

"A vision for the future is more autonomous sensor webs that can act on their own and communicate," says Botts. Eventually, he says, Open GIS officials envision users combining data from different sensor networks and arranging it in a spatial display. For example, the U.S. Environmental Protection Agency could combine real-time sensor data collected from near a chemical spill with sensor-based wind data to determine the size and direction of a chemical plume caused by the spill.

And a company might combine data from sensors on cargo containers in transit to a factory with production data so that it can operate continuously at the lowest possible inventory level.

"The standards all started to develop a level of interoperability that doesn't exist today," says Reed. "The impact on corporate IT is that companies can benefit from information throughout the decision cycle. They will have an ability to insert new plug-and-play technologies to synthesize data. This will also bring down the cost of accessing information."

Sensors for Biomechanics
Source: Microstrain Inc.

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Copyright © 2004 IDG Communications, Inc.

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