image title

Pogo pack: ASU innovator creates wearable, trail tech — and we put it to the test

ASU engineer's latest exoskeleton device aims to help hikers carry heavy loads.
April 14, 2017

Thomas Sugar — creator of the running jet pack and the Spider-Man suit — designs exoskeleton to carry heavy loads

There are two truths in backpacking: You will labor like a pack mule, and you will savor views most people never see.

As a backpacker, you love your gear. It keeps you comfy, healthy and happy in some god-awful conditions. Without it, you would lose your way, your lunch and your life.

At the same time, you hate that murderous, spine-crushing, thigh-melting heap of misery strapped to your back. That’s true even after you’ve honed and mastered your own system over decades. You’ve stripped down, streamlined and efficiency-maximized every ounce hanging between your shoulder blades. And it’s still miserable.

Let’s face it: The technology hasn’t really changed since somebody thousands of years ago attached straps to a bag and threw it on their back, despite what the marketing departments of outdoor retailers claim. “Revolutionary XYZ suspension system! You’ll hardly notice it’s there!”

You’ll notice it’s there. What’s there is the crux of the problem and the laws of physics: There’s 40, 50, 60, even 90 pounds on your back that’s hard to ignore, much less make go away.

• • •

Thomas Sugar at Arizona State University’s Human Machine Integration Lab works on problems like this. A mechanical engineering professor, Sugar and his team build exoskeletons — wearable robotics — that help people perform tasks or survive harsh environments. The Army came to him and asked him to come up with a way to make carrying a heavy load easier.

Read more: Sugar to host, present at robotics conference in Phoenix

He came up with an oscillating backpack. There’s a load-bearing shoulder harness attached to a back frame like every backpack has, with a hip belt and sternum strap. On the back are powerful springs driving a plate up and down, mechanical components, a circuit board, battery and wiring.

After Sugar and his team came up with the concept and design, engineering associate Eduardo Fernandez built the pack in two weekends. The shoulder harness was from a Marine Force Recon pack.

The Pogo Suit was designed to decrease the metabolic cost of carrying a heavy infantryman’s load, around 70 to 120 pounds. The suit does this by oscillating the load up and down at just the right time. Components predict when the next step will take place in milliseconds. When done correctly, the load’s impulse force is minimized.

“Imagine when you’re running with a school backpack,” Sugar said, “just a small backpack, and it’s slamming down on your shoulders at the wrong time, and it doesn’t feel good. This one goes in the opposite direction. It oscillates to make the backpack feel lighter.”

• • •

Does it work? Is the Pogo Suit the Holy Grail of the trail? We wanted to field-test the prototype in the wilderness. This had to be a real trip, carrying real supplies and gear to an objective and back, not an afternoon dry run up an urban mountain with deadweight. Plus, it’s just cool to test something unique. It’s the only pack in the world that oscillates to make the wearer feel better, and there’s only one of them.

“I’ve never seen one of those before!” an excited hiker exclaimed on the trail. “What is that thing?”

We took the Pogo Suit out to the Peralta Trail in the Superstition Mountains east of metro Phoenix. Objective: a 2-mile climb with 1,400 feet of elevation gain up to Fremont Saddle, dropping down the other side until we found water and made camp, then out the next day.

Plug in a lithium ion battery, switch it on, and a light blinks before the Pogo Suit starts to react. A perforated plate on the back about 10 inches wide by 16 inches long is the load-bearing surface. This part rises up and down as you hike.

On flat surfaces, the pack’s mechanics didn’t make that much of a difference. On steep hills, it really came into its own. When you’re doing those steep thigh-burner steps, at the moment you’d really feel the full weight of the load pulling down and back, it’s like a giant hand coming along and lifting the pack off your back for a split second.

It’s a really amazing feeling, after decades of backpacking, to have a giant hand come down and hold your pack up at a crucial second. It’s completely unexpected. It’s like suddenly being able to fly or breathe underwater or grab a hot coal.

One quirk is the noise. It screeches and grinds and shrieks. Does it have issues? Yes. But it’s a prototype, not a market-ready product, so it’s not fair to say it doesn’t have this, that or the other thing.

close-up of Pogo Pack

A hiker tries out the Pogo Pack on the 
Peralta Trail in the Superstition Mountains.

Photos by Ken Fagan/ASU Now

“We thought it was an angry animal,” one woman said coming around the corner to where we took a break from the 92-degree heat.

Another issue is that it doesn’t stop doing its thing after you’ve stopped for a breather. Stand and pant, and it jerks you around like a marionette.

And the Pogo Suit didn’t fare well in the lab. Sugar and his team saw a metabolic cost decrease, but only enough to justify the suit’s 12-pound weight itself. The Army lost interest, but joked they’d buy it just to beat up recruits.

“The drawback was that it did make the backpack heavier,” Sugar said. “You have the motor and frame that oscillates back and forth. It’s not a commercial prototype at this point. … We would need to make it simpler and lighter.”

With improvements, is there a possibility oscillating packs will be sold at REI 10 years from now?

“Maybe, if you could get the costs down, and the battery technology,” Sugar said. “You’d have to somehow be able to charge those batteries for a couple of days. You could carry a solar panel or some fuel and a little generator and charge batteries that way.”

• • •

Packs such as these are the future. There is a cross-pollination between the military and outdoor gear makers. Sometimes soldiers adopt commercial gear. Outdoorsmen will buy military surplus and cannibalize it. (White-water rafting came about through a huge surplus of World War II rafts.)

“I think this could be used recreationally, like let’s say you wanted to hike some of the Grand Canyon,” Sugar said. “We have talked about a rental business for exoskeletons. They cost a lot right now, but if you rent them, you could hike the Grand Canyon and back out. I think that could be a first stage. That would be neat.”

Sugar will present his work — which includes a jet pack exoskeleton enabling a wearer to run a four-minute mile, a Spider-Man suit that can climb any surface, and a cool suit that lowers ambient body temperatures 20 degrees — this month at WearRAcon, the Wearable Robotics Association Conference organized by the Wearable Robotics Association, from April 19–21 in Phoenix. The conference will cover areas including health and fitness monitoring, recreation, business and military applications.

Sugar will have some of his suits on hand and will take questions. He’s pleased with the progress of his latest gadget, and he’s already thinking up improvements.

“I’m excited to hear on your hike it was really helping you go uphill,” Sugar said. He added later, “This was the first real-world attempt that anyone made.”

Videos by Ken Fagan/ASU Now

ASU researcher may have answer for why cave animals go blind

Study undermines Darwin's suggestion of 'disuse'

April 17, 2017

Why do animals that live in caves become blind? This question has long intrigued scientists and been the subject of hot debate.

Clearly, across the animal kingdom, blindness has evolved repeatedly.  There are thousands of underground and cave-dwelling species, from naked mole rats to bats, and many have lost their sense of sight.  A well-studied blind cavefish (bottom), the Mexican tetra (Astyanax mexicanus), is a small, docile, pink-hued fish just a few centimeters long that could easily make its home in an aquarium. ASU evolutionary biologist Reed Cartwright chose this Mexican tetra because there is also a surface-dwelling form (top) that has retained its sight. Photo courtesy of Martina Bradic, New York University Download Full Image

Charles Darwin originally suggested that eyes could be lost by “disuse” over time. But Reed Cartwright, an ASU evolutionary biologist in the School of Life Sciences and researcher at the Biodesign Institute, may be proving Darwin wrong in a recent publication in the journal BMC Evolutionary Biology.

“We think that blindness in cavefish is indeed Darwinian, but ultimately this disproves Darwin’s original hypothesis of ‘disuse’,” Cartwright said. In new research, he explains that eyes are not lost by disuse, but rather a demonstration of Darwin’s fundamental theory of natural selection at work — with blindness selected as favorable and the fittest — for living in a cave.

Go fish

For their work, his research team choose to model a well-studied blind cavefish, the Mexican tetra (Astyanax mexicanus), a small, docile, pink-hued fish just a few centimeters long that could easily make its home in an aquarium.

It’s inhabited caves for 2 million to 3 million years, giving it 5 million generations worth of time to evolve blindness. Cartwright’s group chose this Mexican tetra because there is also a surface-dwelling form that has retained its sight. And for scientists, this built-in comparative power makes it a good choice for further exploration. They have two populations to study that can interbreed and are polar opposites for physical traits.

So Cartwright’s group decided to use computational power to investigate how multiple evolutionary mechanisms interact to shape the fish that live in caves.

“The problem we have in these caves is that they are connected to the surface, and fish that can see immigrate into the cave and bring genes for sight with them,” Cartwright said. “Under these conditions, we don't typically expect to find such a difference in traits between surface and cave populations. Unless selection was really, really strong.”

How strong? In their model, the selection for blindness would need to be about 48 times stronger than the immigration rate for Mexican tetras to evolve blindness in caves. Cartwright’s group estimates that a measure of fitness for blindness, called the selection coefficient, in the tetra is between 0.5 percent and 50 percent.  

These coefficients are high enough that laboratory experiments should have detected a difference between surface and cave forms of the fish; however, none have to date.

Why do animals become blind? Charles Darwin originally suggested that eyes could be lost by disuse over time. But Reed Cartwright, an ASU evolutionary biologist in the School of Life Sciences and researcher at the Biodesign Institute may be proving Darwin wrong in a recent publication in the journal BMC Evolutionary Biology.

Blinded by the light

Cartwright’s team turned to a hypothesis going all the way back to a letter to the editor of Nature in 1925 by E. Ray Lankester, that essentially stated that the reason you have blindness in caves is because the fish that can see simply leave.

“If sighted fish swim towards the light, the only fish that stay in the cave are blind fish. They aren’t trying to get to the light anymore because they can’t see it. Which actually is a form of selection, and thus, Darwinian evolution in action,” Cartwright said.

According to Cartwright, explaining a fitness difference as big as 10 percent between sighted and blind fish may be difficult, “Iosing eyes might not give you 10 percent more offspring. However, if 10 percent of your seeing-eye fish leave the cave, the migration rate is reasonably low, and that could be enough.”

If over time, enough of the seeing-eye fish are systematically being removed, they will also be removed from the gene pool, and that could be enough to drive the evolutionary process.

It could be this sort of habitat preference that maintains the local blind fish population, and the fish that can see are preferentially moving out of the cave. “We found that even a low level of preferential emigration, e.g. 2 percent, would provide a significant boost to local adaptation and the evolution of blindness in caves.”

Cartwright’s team hopes that field biologists begin to consider Lankester's 90-year old hypothesis when studying cavefish. “It would be great if someone could develop a study to test Lankester's hypothesis and whether it is driving the evolution of blindness in caves. That would really help answer one of the questions that have intrigued biologists for over a century.”

Cartwright’s research was supported by National Science Foundation Advances in Bioinformatics program and Arizona State University’s School of Life Sciences and Barrett, The Honors College

Joe Caspermeyer

Manager (natural sciences), Media Relations & Strategic Communications