U.S. Army
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Army Converts Heat to Electricity for Robots

May 4, 2020
Robotic systems may eventually replace human soldiers in the field—if they can efficiently and effectively be supplied with suitable power supplies under stressful operating conditions.

Robotic systems will one day serve as invaluable warfighting partners in the field if they do not run out of power. Fortunately, U.S. Army researchers may have found a way to keep autonomous vehicles and other robotic systems charged using an energy-efficient generator initially intended for private residences. The U.S. Army Combat Capabilities Development Command’s (CCDC) Army Research Laboratory (ARL) at Aberdeen Proving Ground, MD, and a team of research partners, is evaluating the Stirling cycle generator as the solution for providing rechargeable energy to robots in the field.

The researchers are exploring how to convert all possible energy sources, including wood and fossil fuels, into electricity in the field. Justin Shumaker, the ARL’s lead researcher on the project, believes that thermal differences can also be turned into electricity and that it is the first time a Stirling generator of this scale has been used for propulsion on an autonomous ground vehicle (see the figure). “For a Stirling engine to operate, there needs to be a temperature difference between the hot and cold ends,” Shumaker said. “The cooling loop removes heat from the cold end to keep it cold.”

To transform power from the Stirling generator to the autonomous vehicle, the researchers have experimented with several technologies, including a DC-DC power converter that efficiently transforms electrical power from the Stirling generator to the vehicle’s electrical bus. The research has also involved massive modification of a warthog unmanned ground vehicle (UGV) from Clearpath Robotics for use with the Stirling power supply. Only the chassis and wheels remained after the modifications on the large all-terrain UGV which is designed to travel on land and in water.

The new power supply includes a novel battery for energy storage, based on lithium-titanate cells, a battery management system, and a cooling loop to enhance reliability. According to Shumaker, “This all has to be done in a way that integrates well with the vehicle, is reliable, has enough headroom to operate on very hot days, and uses very little electricity for the pumps and fans.” He added, “One day, autonomous robots will outperform soldiers at certain tasks and do so without the requirement of eating, sleeping, or resting. This has the greatest potential benefit to the soldier, removing them from harm’s way.”

U.S. Army Research Laboratory, https://www.arl.army.mil/

About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

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