—by Richard Mandel

Supported by a contract with the Office of Naval Research, Penn State engineers have optimized an energy harvesting circuit that can generate 50 milliwatts of electrical power out of vibration — the ordinary shakes and rattles generated by human motion or machine operation. Although they haven’t tried it, they believe the motion of a runner could be harnessed to generate enough power to run a portable electronic music device. By comparison, simple, un-optimized energy harvesting circuits — for example, the type used to power LEDs on “smart” skis — can only generate a few milliwatts. The researchers say the new circuit offers an alternative to disposable batteries for wearable electronic devices or for wireless communication systems. Dr. George A. Lesieutre, professor of aerospace engineering and associate director of the Penn State Center for Acoustics and Vibration, explains that, like other energy harvesting circuits, the device depends on the fact that piezo-electric materials, when flexing through vibration, produce AC current and voltage. This electrical power must be rectified into DC for use or storage in a battery. Dr. Heath Hofmann, assistant professor of electrical engineering, adds that the magnitude of the piezoelectric material’s vibration determines the magnitude of the voltage. “In operation,” says Hofmann, “the amount of vibrations can vary widely, so a way needed to be found to adapt and improve power flow as well as convert it from AC to DC.” Using an approach similar to one used to maximize power from solar cells, the team developed a circuit for their analytical model that includes an AC-DC rectifier and a switch-mode DC-DC converter to control the energy flow into the battery. An adaptive tracking feature allows the DC-DC converter to continuously implement optimal power transfer, achieving about 80% of the theoretical maximum — well above the operating output of simple energy harvesting circuits Penn State University AG or connect directly at www.rsleads.com/211df-122

Mechanics may have less work inspecting aircraft for corrosion if they implement technology being developed by a Northrop Grumman Corporation-led team. Wide-area Non-Destructive Inspection (NDI) imaging technology will allow inspectors to image surface corrosion beneath paint, rapidly characterizing large aircraft parts quantitatively in a single session while easily documenting the results for comparison with future inspections. Northrop’s Integrated Systems is working with Thermal Wave Imaging, Inc, a supplier of active thermography inspection systems, and with the Naval Air Warfare Center in Patuxent River, MD. “We believe this technology could eliminate two weeks from each cycle’s time and labor associated with the paint removal process,” said Robert Klein, VP, Engineering, Logistics and Technology, Airborne Early Warning & Electronic Warfare (AEW&EW) Systems. “It is an expansion of the thermographic NDI technology we are already applying at St. Augustine, FL.” Integrated Systems’ AEW&EW Systems business area has been developing this imaging technology to scan rapidly painted structures for surface and subsurface corrosion, part of a program that intends to combine multiple methods for wide-area nondestructive aircraft inspection into a single measurement system. Northrup Grumman Corp, or connect directly at www.rsleads.com/211df-123