Helping Soldiers Take a Load Off

November 2010
By Rita Boland


The U.S. Army is looking into the Human Universal Load Carrier (HULC) as part of the solution to reduce the weight of the loads troops have to carry in theater.

Wearable device is capable of carrying hundreds of pounds, transferring that bulk off of people and onto the ground.

The great green Hulk of comic-book lore becomes superstrong when angered. Now, the U.S. Army is investigating a tool with a similar name that will allow warfighters to extend their strength, enabling them to carry heavy weights without straining their bodies—and without the need to take on a broccoli-like hue. By equipping troops with an exoskeleton, developers believe they can help reduce military members’ burdens and assist them in better conducting their missions.

This robotic exoskeleton is called HULC, for Human Universal Load Carrier, and it is designed to augment soldiers’ strength and endurance while reducing load carriage injuries and exhaustion. HULC takes the weight off of troops and transfers it to the ground through the robotic legs of the lower-body exoskeleton. The Army’s Natick Soldier Research, Development and Engineering Center awarded $1.1 million to Lockheed Martin Corporation to develop further the early version of the exoskeleton and to test an advanced ruggedized design.

Upgrades as part of this contract will include optimized control software, extended battery life and enhanced efficiency as well as human factors improvements. Developers also are looking to make enhancements for quicker and easier sizing of the devices for individual users and to increase the overall durability of the system. The untethered, battery-powered, hydraulic-actuated anthropomorphic exoskeleton facilitates deep squats, crawls and upper-body lifting with minimal human exertion. HULC has an advanced onboard microcomputer to help ensure that it moves in concert with the operator. The batteries power the hydraulic system that controls the motion of the robotic legs of the lower-body exoskeleton, and they power a variety of sensors that are processed through an advanced algorithm to discern what the user intends to do. Scheduled improvements also include better control software for enhanced tracking of the user’s movements.

At its most basic level, HULC is intended to help carry loads and reduce fatigue. “One of the big terms we’re using these days is ‘unburden,’” says David Audet, team leader of the Soldier Mobility and Mission Enhancement Team at the Natick Soldier Research, Development and Engineering Center. Soldiers in theater are carrying loads ranging from 50 pounds up to approximately 140 pounds. Transporting that type of weight for any length of time is physically exhausting, especially in extreme heat. That problem is not one to take lightly, Audet states. According to him, Natick has been interested in exoskeletal technologies for several years and believes that HULC is a possible solution toward unburdening soldiers and addressing their loads in general. The device is currently capable of carrying up to 200 pounds.

Even with HULC, users would have to carry some of their equipment on their bodies in case they have to desert the device for reasons such as it running out of power, the need to move quicker or health and evacuation issues. Soldiers also will need to wear issued body armor on their persons as well as other protective equipment, weapons, ammunition and communications devices.

Who exactly will use HULC and what form the exoskeleton will take are factors that will be fleshed out during testing and development. In the current phase of the project, the Army is determining which types of warfighter would benefit from HULC. The military branch does not intend to field the device to infantry troops, but instead to specialty occupations. Audet explains that potential recipients include the chemical community, military police, explosive ordnance disposal personnel, and logistics and sustainment support troops. The soldier center is working with personnel at the Army Maneuver Center of Excellence at Fort Benning, Georgia, to make decisions about the best fit for the technology.

Lockheed Martin HULC Program Manager Jim Ni says that his company will work with individual customer communities to tailor the exoskeleton for their specific needs. “The HULC can be used as a backbone for integrated systems, such as armor, sensors, heating or cooling,” he says. Lockheed Martin also is exploring industrial and medical applications for the HULC and other ground soldier technologies.

In addition to examining which military occupations would derive the most value from a load-bearing exoskeleton, developers are looking into different variations of the devices themselves. One aspect experts are evaluating is how to provide the necessary power and energy to HULC. Audet shares that converting power to actual soldier-helping activities includes different factors. “Energy isn’t free,” he explains, meaning that to obtain power from the exoskeleton, power must be put in. Developers have to come up with a marriage between the device and the soldier that provides the help troops need with energy that can last a long time.

Project personnel are experimenting with different power sources, including the military-standard rechargeable batteries, which are expected to increase operational runtime. Lockheed Martin is partnering with Protonex Technology Corporation to develop fuel-cell power sources in an effort to find more options for HULC. The different variants of the device require different amounts of power, and the versions also require different strength augmentations depending on the amount of equipment carried by the soldiers who would use them. Lockheed Martin additionally is working on a lift assist device attachment that could help users pick up heavy objects.

Audet says that as the Army determines the best fit for the exoskeleton in the field, the lifting capability is a piece of equipment it might fund. But, he says, much fundamental development remains to ensure soldier safety and value added to the warfighter. “That’s something we don’t take lightly here at Natick,” he states, adding that “It’s not a given [HULC] will be fielded.”

In addition to the other requirements that must be reached for the system to succeed, HULC also has to be universal, meaning it would be applicable in all environments. In the current version’s development, Natick personnel are working on requirements from Fort Benning such as studying how the device handles submersion, high humidity, abrasion and impact after being dropped from several feet high. Though the current manifestation of  HULC is called a version, no exoskeletal device has been fielded to troops.


A lift assist device that could be added to HULC helps warfighters lift heavy items without restricting normal range of motion.

Ni explains that the previous HULC design was a laboratory prototype, and that the new ruggedized version incorporates multiple design changes to increase reliability and performance in operational environments. New environmental sealing and packaging give the system’s electronics increased protection from natural and battlefield elements.  HULC’s form and fit have been further refined as well, allowing the operator to adapt to the exoskeleton in a shorter period of time. “The ruggedized structure allows for rapid, repeatable and tool-less adjustments to the torso and thigh length to better suit a wider variety of users,” Ni says. The new ruggedized design also enables users to evaluate the system in operational environments. Additional benefits include HULC’s ability to conform to the body and the incorporation of lumbar padding for comfort and support.

Lockheed Martin is working with Berkeley Bionics to develop HULC, building on the smaller company’s experience creating exoskeleton systems. Using a more rugged design than previous versions, the team members intend to introduce the concept of an anthropomorphic exoskeleton for experiments and evaluations. Through testing, the military can determine the advantages of the device for particular missions.

The private sector and Army personnel involved with the project are working hand-in-hand to advance HULC in a way that will benefit troops. Developers are measuring and comparing the physiological effort required for soldiers to walk two miles with 100-pound loads with and without the devices. They also are observing the exoskeletons from the biomechanical perspective to see how HULC interacts with soldiers such as how gait affects the impact of the device and how it rubs or creates fatigue in the soldiers. Audet says that through the work, Natick can tell Lockheed Martin about improvements the Army would like to see.

Audet’s colleague Dr. Jeffrey Schiffman, the team leader of the biomechanical team at Natick, explains that the center is performing many laboratory-based studies to evaluate straightforward walking with and without the device and with and without some sort of load as well as to monitor oxygen consumption and heart rate. Ni says that treadmill testing will measure anticipated decreases in metabolic cost as HULC assists the user with heavy loads. The necessary wind, rain, temperature and humidity testing will replicate harsh environments and verify combat durability. The information is provided to HULC engineers so they can tweak the device’s power system. Hard scientists and engineers also interact with experts in human factors to incorporate information from those fields.

Studies are run under two-tier Institutional Review Board (IRB) oversight. First, studies go through the local Natick IRB and then to the “Big Army” board. Natick’s partnership with Fort Benning helps the research and development center determine valid tests that could run in a laboratory to equate to field conditions. A field test that will include soldiers and Marines is scheduled for next summer at Fort Benning. Through the various studies, scientists can compare past data to that coming out of the laboratory to identify the necessary steps forward.

If the tests go well, a joint decision to field HULC likely will be made among Natick, the Maneuver Center of Excellence and the user community, Audet says. However, estimating an eventual rollout date would be premature. Much will depend on soldier feedback and the field evaluations that will be done at the end of the current phase. Other determining factors include how HULC performs in the laboratory and whether developers see a significant advantage for soldiers using the devices versus those without them. Audet says Lockheed Martin’s approach going forward also will influence eventual fielding.

Actual acquisition and distribution to combat troops probably would be conducted through one of the Army’s program executive offices. Audet explains that Natick would work with the office to transfer the technology to the next phase of the development.

Natick Soldier Research, Development and Engineering Center:
Army Maneuver Center of Excellence:
Lockheed Martin:
Berkeley Bionics:


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