Take a Load Off

Military service members, firefighters and people with mobility disorders will soon be leaning on new innovations to help them achieve their goals. Exoskelton research in robotic technology has long been considered science of the future but is proving to be very much in the present. HULC, which stands for Human Universal Load Carrier, is the latest of a series of exoskeletons being created by Berkeley Bionics, a start up originating from the University of California (UC) Berkeley.

What began with a grant from the Defense Advanced Research Projects Agency (DARPA) in 2000 has produced four prototype exoskeletons that seek to augment human performance. According to the company Web site, researchers at Berkeley Bionics analyze human motions in real-life environments and employ “non-traditional approaches to electromechanical design, control sciences, and power delivery systems to design and build state-of-the-art load-carrying, computer controlled exoskeletons for applications that demand robustness and performance.”

Berkeley Bionics founder, Homayoon Kazerooni, PhD, professor at UC Berkeley, director of the Berkeley Robotics and Human Engineering Laboratory and one of the world’s leading experts on Robotic Human Augmentation spoke to O&P Business News about the advancements they are making in exoskeleton technology.


Exoskeleton technology
All images reprinted with the permission of Berkeley Bionics.

There are many purposes that an exoskeleton aims to fulfill but in its infancy, exoskeleton technology was developed to literally “take a load off” of the wearer’s back.

Kazerooni explained that biomechanics research suggests that people should carry no more than one-third of their own weight on their back in a backpack or other carrying device. Looking at military applications of exoskeleton technology, it became evident that the average service member carries loads upwards of 130 pounds, Kazerooni explained at a presentation of the American Academy of Orthotists and Prosthetists earlier this year.

“These machines allow you to carry much more than that because you won’t feel the load,” Kazerooni told O&P Business News. “The machine takes the load.”

Beyond the military application, Kazerooni also explained two additional applications of the prototype technologies including a civilian use for mountain climbers and firefighters as well as a medical application for people suffering with mobility disorders due to either a neurological or musculoskeletal disorder or for post-stroke patients.

Berkeley Bionics is currently exploring all three sectors for future implementation.


The evolution of exoskeleton technology at Berkeley Bionics began in 2003 with the development of a device called BLEEX.

“BLEEX was the very first internally powered robotic exoskeleton that we designed and built,” Kazerooni said of the technological breakthrough. “All our exoskeletons have on-board power sources. They don’t have any cables connected to them and they [are equipped] with power supplies.”

Although this first device was only laboratory evaluated, it paved the way for future evolution which led to the Exohiker in early 2005.

According to the Berkeley Bionics Web site, the Exohiker was developed for “carrying heavy loads on long missions.” It weighed only 31 pounds including the power unit, batteries and computer device and could carry 150 pounds while being virtually imperceptible in terms of noise output.

Kazerooni added that the device allowed the wearer to walk comfortably but was not designed to handle terrain changes such as steep hills.

“Exohiker still lets you carry loads on hills but primarily was designed for regular terrain, not steep [terrain] and not for stairs,” Kazerooni said. “It still allows you to do it but was not perfectly designed for [those situations].”

The successor to the Exohiker was a device called the Exoclimber which closely followed the release of its predecessor in late 2005.

The Exoclimber was developed to answer one of the deficiencies of the Exohiker — steep terrain management. According to the Berkeley Bionics Web site, “Exoclimber is designed to allow rapid ascent of stairs and steep slopes while providing the same long term load carrying capability of Exohiker.”

At a weight of 50 pounds, this device could carry up to 150 pounds to the top of the Empire State Building at 1200 feet with only one two-pound battery, according to the Web site. It also boasts that the machine is as quiet as an office printer.

Exoclimber was successfully military evaluated with great reviews.

“The military evaluation of ExoClimber was spectacular,” Kazerooni said. “The users love the device.”


BLEEX Exoclimber
BLEEX was developed by Berkeley Bionics in 2003. The Exoclimber, released in late 2005, is better suited for steep terrain according to Kazerooni.

Berkeley Bionics’ latest exoskeleton combines the positive attributes of precursors BLEEX, Exohiker and Exoclimber and goes one step further in terms of energy output. HULC was introduced in July 2007.

“HULC has one more characteristic that our previous exoskeletons did not have. HULC and [previous] exoskeletons are able to carry loads of about 150 to 200 pounds however HULC is also able to reduce the oxygen consumption of the wearer,” Kazerooni explained. “According to our experiments, [HULC wearers use] up to 15% less oxygen so that means it is not only augmenting your strength to lift heavy objects but also it is giving you endurance.”

Using HULC, wearers can carry up to 200 pounds while also decreasing their metabolic cost.

“You can go further because you are using less energy,” Kazerooni explained. “Oxygen is an indication of energy. Your metabolic cost of locomotion is lessened by 15%. That is the fundamental difference. That is why HULC was invented. There is no other device in the world that does that.”

HULC uses an electrohydraulic system and is battery powered. When asked about the duration of the battery power Kazerooni explained that the duration is dependent upon the terrain and speed at which the wearer is moving.

“If you are going up stairs or hills, then you are using more power and if you’re going down stairs, you would use less,” he said. “It is targeted that the machine can last for one day of normal maneuvers operating solely on batteries, regardless of load.”

Additionally setting the HULC apart from previous exoskeleton technologies is that the machine has an improved performance and smoother response while also encompassing the strides made in those initial attempts.

So far, HULC has been evaluated in the laboratory and also through preliminary field evaluations but Kazerooni said that no scientific conclusions have been deduced yet.


The future of exoskeleton technology is one that is rapidly changing and progressing. Kazerooni and the team at Berkeley Bionics will travel two paths over the next two years with the future of these advancements–continuing the mission of HULC and the development of two medical exoskeleton devices.

HULC is the latest exoskeleton released by Berkeley Bionics. For proprietary reasons, certain aspects of the image have been blurred.

“HULC will continue to be improved over the next 18 months when it will be ready for field evaluations at various locations,” he said.

Following a favorable response as a result of field evaluation, Kazerooni is expecting to go forward with the HULC technology with various agencies.

“We don’t know the details yet and when the Department of Defense will make a decision. There is really no other exoskeleton even close to this stage,” Kazerooni said.

After the 18 month period, he is expecting that HULC will be complete and field evaluable.

“On other medical exoskeleton systems, we have about one year to go. Within the next six months we are going to evaluate our first system for post-stroke patients and then we have another exoskeleton which we will be evaluating in people with spinal cord injury within 18 months.”

Upon completion, the post-stroke medical exoskeleton will be a rehabilitation device, not as assistive device.

“It is a device that allows stroke patients to learn to walk again gracefully,” Kazerooni said.

The exoskeleton being designed by Berkeley Bionics for patients with limited or no mobility will be coming out within the next few years, Kazerooni said.

“I think the next two or three years are very busy for all of us,” he said about the future of this technology. “I predict in no more than 2 to 3 years we will have this technology in this area and it will be pushed forward. Hopefully a lot of people who haven’t been able to walk will be walking.”

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Jennifer Hoydicz is the managing editor of O&P Business News.

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