ABERDEEN PROVING GROUND, Md. (April 10, 2018) - - The Army's target for missions to last 72 hours and beyond without battery resupply may someday get a boost from Soldiers' footsteps.
The U.S. Army's Communications-Electronics Research, Development and Engineering Center, or CERDEC, is developing energy-harvesting technologies that will convert Soldiers' natural movements into usable energy that could soon power Soldier-wearable electronic devices, night vision goggles and radios. By harvesting kinetic energy, Soldiers will require fewer batteries and achieve lighter loads to conduct modern expeditionary warfare.
"Our future forces will require power and energy technologies that are lighter weight and longer lasting for enhanced mobility, Soldier lethality and energy independence," said Beth Ferry, Power Division chief for CERDEC's Command Power and Integration directorate, or CP&ID.
"Many of our science and technology investments aim to provide continuous power for Soldiers and small units operating dismounted in remote areas, for multiple days and under harsh environments."
As the Army's applied research and advanced technology development center for command, control, communications, computers, cyber, intelligence, surveillance and reconnaissance - or C5ISR - innovation, CERDEC develops and matures capabilities that support Army Modernization priorities and enable tactical overmatch for the joint warfighter.
"CERDEC's state-of-the-art power technologies align with the Army's modernization priorities, which aim to leverage innovative science and technology prototypes, demonstrators and Soldier feedback," Ferry said.
No single human motion produces enough excess power, without injury, to charge MIL-STD batteries in a reasonable amount of time, so CERDEC is investigating an entire suite of alternative energy options that will work in tandem to achieve tactical energy independence for the Soldier and small unit. These include efforts to leverage standard Soldier equipment, such as combat boots and rucksacks.
"We embedded an energy-harvesting mechanism into a combat boot heel insole so that each time a Soldier's heel strikes it activates a generator, which spins to produce energy," said Nathan Sharpes, CERDEC CP&ID engineer.
Sharpes recently engineered two improvements to the heel-strike insole harvester, which are under patent pending.
"We improved the mechanism by making each step feel more natural versus the slight sinking motion Soldiers experienced when using our previous version," Sharpes said.
Engineers also examined the counter-torque forces produced from the generator's spinning mechanism, and produced a user-friendly design that works with the body to offset the counter-torque for a more comfortable step, Sharpes said.
"We also sped up the generator's timing mechanism to produce energy for longer than the previous version, which is a positive direction to achieve harvester efficiency," Sharpes said.
CERDEC's Energy Harvesting Assault Pack, or EHAP, is another CERDEC technology that converts Soldier movement into power. The EHAP consists of a rack-and-pinion generator with a spring-loaded, double-frame suspension system attached to a standard rucksack.
With each step, the rucksack glides up and down while the generator captures small amounts of kinetic energy and converts it into useable electrical energy that would otherwise be lost.
"Soldiers must be able to quickly move, shoot and communicate, hauling anywhere from 35 -- 135 pounds in their rucksacks, so energy-generating packs shouldn't add to the Soldiers' fatigue or decrease their maneuverability," said Julie Douglas, CERDEC CP&ID engineer.
Energy generated from the EHAP is typically harvested into the Integrated Soldier Power & Data System, or ISPDS, which charges the conformal wearable battery - a lightweight wearable, flat and flexible battery also developed by CERDEC.
"The ISPDS is a power hub; it is to Soldier power as the Atlanta airport is to travel," Sharpes said. "It routes power in and out to wherever is needed. Used with the EHAP, it distributes the energy stored in the conformal wearable battery to all the Soldier-wearable electronic equipment."
Future iterations are focusing on lessening the Soldier's load, and CERDEC is committed to reducing the EHAP's weight by at least half, Douglas said.
Sharpes is also developing a boot-mounted technology to harvest energy from the torque around the ankle. The harvester is embedded into the midsole of a combat boot and includes a bracing structure that goes up the boot top.
"The body does not produce enough excess motion energy at any one location, so we have to look to other areas of the body to find more energy," Sharpes said. "The ankle experiences the largest torque of any joint in your body, so it is a great source for an energy harvester."
The harvested energy from the boot-mounted harvester could eventually be used locally on the boot to power the next low-power iteration of the Micro-Inertial Navigation Technology, or MINT, which is a dead-reckoning navigation device for GPS-denied environments such as inside buildings, forests and tunnels. CERDEC's positioning, navigation and timing, or PNT, subject matter experts partnered with the Defense Advanced Research Projects Agency and Carnegie Mellon National Robotics Engineering Center to perform initial testing on the boot, which is still under research and development.
CERDEC has also teamed with biomechanical engineering experts at the Army Research Lab Human Research and Engineering directorate to determine how much energy the body produces for these energy-harvesting devices. Soldier volunteers undergo tests on instrumented treadmills to capture motion, document joint angles and measure breathing to determine how much effort they would expend while carrying weapons.
"We hope that our science and technology advances will eventually generate as much power as Soldiers need for their missions," Douglas said. "When this net-zero energy solution also takes the weight off of the Soldier, our Army will be even better equipped to deploy an expeditionary, mobile force."