LAKE WALES, Fla. — DARPA is working on a new way to power war-zone sensors that watch over roads U.S. armed forces travel. The U.S. Defense Advance Research Project Agency's (DARPA) Troy Olsson described its Near Zero Power Radio Frequency and Sensor Operations (N-Zero) in a keynote (Monday Oct. 31) at the IEEE Sensor 2016 conference in Orlando, Florida (Oct.30-Nov.2).
By 2018 the DARPA's N-Zero initiative aims to have deployable sensor networks that require near-zero standby-power, a goal the team quickly found that was impossible without microelectromechanical systems (MEMS). In addition the teams discovered an extra benefit of MEMS — an advantage the team had never imaged possible. MEMS provides not just near-zero standby power, but can be configured for absolute zero standby power by using the power from the signal to be detected itself to power-up the transmitter. And in some situations, the transmitter too can be powered without a battery, by storing up energy on a super-capacitor from renewable sources — from solar to vibration harvesters.
"We wanted to learn how to reduce our sensors power envelope so that we could deploy them right at the tactical edge with a battery that does not need to be replaced for a long period of time," said DARPA program manager Roy (Troy) Olsson in his keynote address titled Event Driven Persistent Sensing: Overcoming The Energy And Lifetime Limitations In Unattended Wireless Sensors obtainable by subscribers to the IEEE Sensors Journal after the conference.
Defense Advanced Research Projects Agency (DARPA) program manager Troy Olsson describers its Near-Zero project to reduce the power to zero standby when deploying tactical sensor networks.
"Now we want the signals themselves to actually power the processing before waking up a more powerful signal-processor and transmitter," said Olsson.
Today U.S. soldiers are being killed because the Defense Department cannot deploy all the sensors it would like to. For instance it could detect when a bad guy is burying an improvised explosive device (IED) if there were power lines along the roads in these foreign countries in which U.S. soldiers fight. DoD could tap their power to deploy sensors every few yards to detect someone digging in the middle of the road to plant an IED. As it is, every sensor deployed today has to be battery powered, so even if vast sensor nets were deployed it would put more soldiers in jeopardy by forcing them to expose themselves to ambush attacks while changing sensor batteries.
Here a widely deployed network of sensors only awaken to transmit the presence of a vehicle at a zero-standby power MEMS microphone detects a vehicle-like noise.
"In combat situations we can't endanger solders just to replace batteries," said Olsson.
Applications of zero-standby power unattended sensors, communications nodes and Internet of Things (IoT) devices perform perimeter monitoring, critical infrastructure protection and monitor battlefield engagements.
The N-Zero effort will enable super-small sensors built from hybrid MEMS and micro-electronics. Depending on the complexity of the sensor and its distance of the nearest high-power RF repeater, some sensors will be able to be sprinkled across the battlefield from drones for constant realtime situational awareness using energy harvesting. Others will have complex sensor arrays aboard and use coin-, AAA- or even AA-sized batteries to transmit a complete compliment of visual, audio, seismic and even radar signals back to home-base for up to 10 years without a battery change.
Zero power MEMS wakeup sensor uses just five mask layers on a silicon-on-insulator (SOI) wafer.
The trick that N-Zero researchers have discovered, is that MEMS sensors work to generate power from signals just by virtue of their microscopic moving internal mechanical parts. From their a hierarchy of MEMS subsystems can stimulate sub-one-volt electronics to process signals and determine if they are false alarms all before even turning on the N-Zero RF transmitter. The transmitter itself need only send a low-power "chirp" signal that identifies its findings without having to send power-consuming raw data.
As a consequence, the N-Zero initiative will not only save soldiers lives, but could drastically reduce the severed limbs suffered at the hands of a-proportional advisories deploying IEDs.
— R. Colin Johnson, Advanced Technology Editor, EE Times