Energy Harvesting Backpack with High Specific Power and Broadband using a Dual Mass-Inerter and Mechanical Motion Rectification
Abstract
With the ever-rising need of electronic equipment in modern warfare, a typical dismounted Marine need to carry 16-20 lbs. of batteries on a 72-hour mission. Demonstrated by the US Army, energy harvesting using a suspended-load backpack provided the largest power than wearable solar panels and knee kinetic energy harvesting devices during the Maneuver Fires Integration Experiment held in 2014. However, traditional energy harvesting backpacks are facing three longstanding challenges: (1) narrow operation bandwidth, (2) low specific power (power per unit load), and (3) large stroke. First, traditional energy harvesting backpacks rely on resonance to achieve maximum power. To harvest large power, the mechanical damping of the backpack is kept low, resulting in a high quality factor and consequently high stroke and narrow resonance. Once the wearer s stride frequency lowers by 20%, the power can decrease by more than 90%, leading to narrow-band and large-stroke energy harvesting. Prof Lei Zuo invented the mechanical motion rectification (MMR), a smart mechanism that converts oscillatory vibration into unidirectional rotation, for which he was awarded the 2018 ASME Leonardo da Vinci Medal. By taking advantages of the unidirectional motion and nonlinear inertia effect in the MMR mechanism, a non-resonance design of packpack energy harvesting has been built at Virginia Tech, which can adaptively adjust the natural frequency to some extent as the stride frequency changes. As a preliminary result, it showed a much broader operation bandwidth during experimental testing: achieving 1.8-4.1 W electricity, at 30 lbs load and 2-3.5 mph, in comparison with the 0.2-2.8 W at 44lbs load and 2-3.5 mph, published in Science. The Virginia Tech’s packpack also shows 3-10 times more specific power than the state-of-the-art energy harvesting backpacks: 0.12W/lb vs 0.01 ~0.04 W/lb at 3 mph in the Science paper and Army CEDEC Ligning backpack. In this project, we propose to investigate and develop a new generation of harvesting backpack, using a dual mass-inerter and mechanical motion rectification, (1) to increase specific power by reaching 0.2-0.26 W/lb (15-20W at 75 lb load) in treadmill tests without increasing the motion stroke, (2) to broaden the bandwidth by achieving 6~28 W of power during the walking speed interval of 2.5~3.5 mph, and (3) to reduce the human fatigue and metabolic cost while harvesting the energy. These goals will be achieved with the four innovations: Increasing the power and reduce the load using dual mass-inerter and MMR, broadening the bandwidth by using the nonlinear mass, modelling the human biomechanics for adaptive harvesting tuning, establishing the human comfort and fatigue criteria. This project will be completed under the lead of energy harvesting expert Prof Lei Zuo (PI) and biomechanics expert Prof Robin Queen (co-PI), with participation of a postdoc and two graduate students.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 26, 2018
- Source ID
- N000141812190
Entities
People
- Lei Zuo
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech