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By Jonna Lilly

"Pneumatic muscles. What will those crazy engineers think of next," I thought. It seemed they were always trying to replicate human function from some angle or another. Artificial vision, artificial hearts, intelligent machines that can talk and understand you when you talk, read your handwriting, even think, reason, and make decisions. "Why? Don't we already have humans who can do these things perfectly well," I thought.

In 1999, my husband John took a sabbatical from his faculty position in the Electrical and Computer Engineering Department at the University of Louisville to go to Wright Patterson Air Force Base in Dayton, Ohio. There he received his first exposure to what they call pneumatic muscles (PMs), cylindrical rubber tubes encased in a plastic sheath wound in a double helix. John explains, "The sheath reminds you of one of those Chinese finger traps that holds your two index fingers. When you try to pull your fingers apart, the trap only gets tighter. To get out, you have to move your fingers closer together and then the trap gets larger so you can remove your fingers." When you pump air into the tube, it inflates and widens. When it widens, it also shortens a few inches due to the helical sheath. When it shortens, it can pull with a large force.

Again, I wondered why researchers were so interested in these things, given that human muscles work just fine. John explained that the military wanted to make human exoskeletons with PMs all over them to give the wearer super strength. A soldier in a PM-powered exoskeleton could run super fast, jump sky high, or lift a Jeep off of someone injured in the field, all of which seemed like a sci-fi film to me.

John drove from Louisville to Dayton to start his sabbatical in January 1999, when Dayton had about a foot of snow on the ground. He was alone but didn't have much to move into his apartment, just a few clothes, books, cooking utensils, and a small TV. We decided I would stay home with our two small children, and he would make the three-hour commute between Louisville and Dayton every week. On the phone that first night in Dayton, John told me he had fallen in the snow between his car and the apartment while carrying in the TV over uneven, slippery ground. He was unhurt, though, except for a face full of snow. The TV made it, too.

I was glad John wasn't going to let his multiple sclerosis (MS) stand in the way of this sabbatical. We had never thought much about his disease because it had never really affected our lives much. We could do pretty much anything we wanted, like go to the mall, go for walks, and play golf. It was getting a bit worse in early 1999, though, so John started using a cane during his sabbatical for the first time.

Meanwhile, the PM research went on. The snow melted, and winter turned to spring. John was working with the scientists at Wright Patterson trying to control the PMs. Despite their simple construction, PMs are difficult to control accurately. Before they could be used in an exoskeleton worn by humans, their length and the force would have to be controlled precisely. The laboratory in which John was working had a single PM hanging vertically with a weight attached to the bottom. "The idea was to inflate and deflate the PM in such a way as to control accurately the vertical position of the weight above the floor. This is not a trivial task, because the PM is highly nonlinear and time-varying, making it a tough system to control accurately," John explains. He told me they were trying many different ideas to control the muscle.

It was not until most of the way through the sabbatical that John and I realized the irony of this situation. MS sufferers have trouble controlling their muscles. They also suffer from lack of strength. What about the PMs? Could they help? When John delved further into PM applications, he found that PMs had already been used for rehabilitation of stroke victims and Parkinson's disease patients. However, these uses had been experimental, and nothing close to a working product for use by the public had emerged from them. The military wanted to concentrate on making super-soldiers. Wouldn't an equally worthy goal be to apply the technology to help disabled people?

To further that goal, John recruited a colleague in U of L's Mechanical Engineering department, Peter Quesada, to help. They agreed to write a new proposal for a grant to continue John's research and expand it. In addition to their input, they would also receive guidance from an industrial engineer who would assist with ergonomics, another mechanical engineer who would concentrate on bone and muscle dynamics, and another electrical engineer to focus on circuitry.

The expectations for this research, according to Quesada, are "to provide the basic tools for fabricating devices to aid individuals, either in rehabilitation or as long-term orthotic devices. I would further expect that some number of functioning prototypes could actually emanate from our work." John still wants to aid the military in their quest for super-soldiers. But we're also hopeful that something to aid MS sufferers will come from this research. John and Peter plan to address both.

John emphasizes that this idea is still in its infancy and that the technology doesn't yet exist for practical applications of PMs in human exoskeletons. However, new science sometimes happens before the means to apply it practically are available. For example, many complex engineering ideas came about in the 1950s, and the advent of the digital computer in the 60s and 70s made their practical use a possibility.

We remain hopeful that someday PMs will aid soldiers, MS sufferers, and all others who require physical help. With luck, perhaps strength-augmenting PM suits will one day be commercially available the way other physical augmentation devices can be obtained now. Arnold Schwarzenegger, watch out!

As an English major and writer, Jonna Lilly has taught at several colleges and universities and written for numerous national publications and websites.

Progressive Engineer
Editor: Tom Gibson
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