Army Wants to Equip Soldiers with a Mechanical Arm to Reduce Fatigue

Army Research Lab engineer Dan Baechle demonstrates how to strap on a mechanical arm designed to reduce soldier fatigue and improve weapon’s accuracy. (Photo: U.S. Army) | By

Army scientists are testing a mechanical "third arm" that they hope will help reduce fatigue and make soldiers more effective with larger weapons.

Engineers at the Army Research Lab have been working the project since 2015 and plan to hold a second round of tests with soldiers this spring, according to a recent Army press release.

The device currently attaches to equipment on the user's back hip and is intended to redistribute weight onto the soldier's abdomen.

"We started out with just trying to think of a way to help improve the lethality for the dismounted soldier," mechanical engineer Dan Baechle said in the release. "

Baechle continued that improving lethality generally means stabilizing the soldier's weapon or giving the soldier a more powerful weapon.

"But also if we're stabilizing the weapon and taking the load off of the soldiers' arms, does that improve the soldier's readiness?" Baechle said. "Does it also improve the soldier's accuracy with the weapon?"

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Last summer, six soldiers volunteered to take part in a pilot study, where researchers placed electromyography sensors to measure muscle activity, according to the release.

Electromyography measures the electrical activity of muscle tissue using electrodes that touch the skin.

Soldiers were tested with and without the mechanical arm.

"We found that it reduced the fatigue and reduced the muscle activation for some soldiers," Baechle said.

Soldier feedback led to design changes such as an extendable hinge plate, so that a single plate can fit soldiers of different sizes and body types. The current prototype weighs 3.5 pounds and can now support weapons such as the M249 squad automatic weapon, according to the release. The SAW weighs about 27 pounds.

"Right now we have a prototype that's essentially a research platform that we're using to investigate different types of materials -- how materials and structures can stabilize a weapon or a shield, reduce fatigue on the soldiers' arms, but also improve accuracy," Baechle said.

Researchers are also testing to see if the device can help reduce recoil on more powerful weapons, the release states.

"You have a lighter-weight weapon but potentially a higher-caliber weapon which normally would increase the recoil on your shoulder," Baechle said. "Could you use third arm and some clever materials on the arm to redirect that recoil back toward the body and thus allow the soldier to wield a higher-energy weapon without necessarily burdening the soldier more?"

Researchers hope to further improve the device to make it more comfortable and further reduce fatigue. The current plan is to test the device this spring in an evaluation involving 15 soldiers, the release states. Baechle said further research must be completed before the device can be fielded.

-- Matthew Cox can be reached at