Robotic Exoskeletons Could Help Soldiers Bear Heavier
Loads
by Joe Pappalardo
August 2004
source: http://nationaldefense.ndia.org/article.cfm?Id=1553
(PHOTO)
Researchers are edging closer to fielding a gas-powered system that
will permit soldiers to effortlessly carry hundreds of pounds of
equipment on the battlefield.
The program, sponsored by the Defense Advanced Research Projects
Agency (DARPA), is paving the way for robotically enhanced
soldiers, but not necessarily futuristic front-line warriors,
caution scientists.
Contractors and the program manager of the exoskeletons for human
performance augmentation (EHPA) said that, while the option for
battle-ready, wearable robotic suits remains open, the system that
is being currently pursued is aimed at allowing soldiers to tote
enormous loads.
This thing is useful for carrying payload, said DARPA project
manager John Main. It could be 200 pounds of food, or it could be
200 pounds of body armor.
The overall goal of EHPA is to develop devices that increase the
speed, strength and endurance of soldiers in combat environments.
When EHPA was launched in 2000, visions of massive power suits that
propelled wearers over buildings and through wallsmainly products
of the fertile imagination of science fiction writer Robert
Heinleinleapt into peoples minds. The reality may be more
mundane, but the challenge remains enormous.
This is a fairly boring transportation program, Main said, with a
small grin. Were not jumping over buildings. Were getting into
rough terrain that is denied to Humvees.
In 2001, six contractors were left to pursue the development of
self-powered, controlled, and wearable strength augmentation
systems. The first challenge was proving that actuatorsmachine
muscleand high-density, man-portable energy sources were
feasible.
In the fall of 2003, two contractorsthe University of
California-Berkeley and Sarcos Research Corp.were chosen to create
the system. Locust USA Inc. of Miami and TIAX LLC, of Cambridge,
Mass., are working on the power source.
The words off-the-shelf are not used much in the exoskeleton
program, Main said, since everything is being built and optimized
specifically for the product. Every part going into the
exoskeleton needs to be designed from the ground up, he
said.
It may be too early to plan around real-world applications, but
military personnel are watching the development of the project.
Those who handle logistics envision exoskeletons loading trucks,
while infantry commanders see the extra weight dedicated to
shielding, Main noted.
If you think about this in terms of airplanes, were about at a
Wright flier, Main said. Three years ago no one thought it would
walk.
Two teams of researchers late last year proved that the idea behind
EHPA was technically possible. Last August, a research team at
University of California-Berkeleys robotics engineering lab
operated their Berkeley lower extremity exoskeleton (BLEXX) from a
tether. The prototype weighs 90 pounds and allows a soldier to
carry 80 extra pounds without feeling it. Sarcos soon followed with
an untethered prototype that could handle 125 pounds.
The two projects are approaching the systems problems in different
ways. At Sarcos, sensors in the foot respond to force and apply a
counter-force that nullifies it and quickly tells actuators in the
joints to bear the load. That way the EHPA wearer does not feel the
greater weight, and does not have to think about operating the
system.
The exoskeleton system at Berkeley responds to what the body is
doing and adjusts its behavior accordingly. For example, the leg
acts differently while the foot is raised in mid-air as opposed to
on the ground. Fast computer processing matches the machine with
the human bodys changing states.
The head of the Berkeley effort, Homi Kazerooni, told National
Defense his team is leaving the future uses for military engineers.
For him the true challenge is to seamlessly integrate and
synchronize the movements of man and machine, not to create a
man-shaped battle tank. We are not thinking of the exoskeleton as
a suit of armor, he said. Were looking at the exoskeleton as a
mobile platform, good for carrying mission-critical systems. This
is a lot different than the movies, or what science fiction authors
write about.
The key is to make a robotic system that can keep up with
split-second demands of human operators. With positive-definite
points of contact at the feet, back and shoulders, coupled with
other compliant sensors at the hip or leg, the system relies on the
scores of linked nodes, placed close to sensors and actuators, to
bond the system in a moveable local area network. The nodes are
arranged in ringsone for each leg, and an additional ring for any
mission-critical electronics gear unrelated to the
exoskeleton.
Agility is a function of the computer and the hardware itself,
Kazerooni summed up. The goal, he added, is to create a machine
thats transparent, one that a wearer can use without feeling it,
as with a garment.
Exoskeletons have the number one most difficult problems in
robotics, said Kazerooni. Were taking on those problems on a
systematic level.
Power supply is as important to exoskeleton systems as design, Main
said. During the last three or four years, weve winnowed down to
three engines, he said. They have to last a minimum of 1,000
hours
The challenge you have is to make a power system that does
what muscles does: convert fuel directly into work.
Given the parameters of military missions, there is a premium on
conserving power. Actuators that mimic muscle cannot waste fuel
while idling, but also must be ready for action in
microseconds.
Kazerooni conceded that robotic enhancements worthy of combat were
feasible, given a system design that could keep up with soldiers
reflexes. Can the machine shadow our reflexes? These are not
voluntary, and sometimes 200 microseconds is not fast
enough.
Kazerooni said that upper body enhancements, focused on arm
strength and automated gripping, are better suited for logistical
support rather than combat since soldiers want their hands free.
We dont know what to do with upper body extremities except
logistics, Kazerooni said. Soldiers never want to lose the
weapons from their hands.
For prototype testing, DARPA turns to the ergonomics experts at the
Armys Natick Soldier Center in Massachusetts. By bringing the
human factor into the development of the EHPA system, designers
hope to circumvent design problems early and ensure that the system
is as transparent as hoped.
What better time is there than when youre building the
equipment? said Jack Obusek, team leader for the ergonomics team
at Natick. We can make quantifiable measurements in movement
patterns and changes in the force on the body of the wearer.
Unpowered prototypes from Sarcos and Berkeley already have been
tested at Natick, and powered tests are scheduled for early next
year. While there, lab scientists will don the leg gear and perform
a series of incremental tests as Natick personnel collect data on
the changes in force patterns on the wearers and examine any
biomechanical shifts induced by the system.
He said that the next round of tests would be very lab-based, but
that the future could hold involve obstacle courses and harsh
terrain.
Still, no one understands the challenges of making a combat-ready
robotic enhancement system like a PhD. in biomechanics, and Obusek
said he doubts the exoskeleton system will be used to knock down
walls or pound down doors in urban combat since any force exerted
must be matched in the opposite directionthe soldier in the suit.
Youve got to remember the laws of physics, he said.
Still, he said EHPA could provide the framework for improved
ballistic armor or medical evacuation equipment, applications that
could find a home in a combat environment.
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