Ani Hsieh’s Robot Teams are Exploring New Frontiers in Penn Engineering

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By Lida Tunesi

As a child, Ani Hsieh wanted to become an astronaut, but she soon realized there were a few obstacles that no amount of studying or training could overcome.

“I’m short, I’m hopelessly nearsighted, and I get really bad motion sickness,” says Hsieh, research associate professor in the Department of Mechanical Engineering and Applied Mechanics. Thankfully, she saw an alternative. “I thought the next best thing would be to be an engineer. If nothing else, I could work on space robots.”

Hsieh did find her way into robotics, but rather than the cosmos, her work primarily focuses on the similarly unknown and isolated world of the oceans.

“Robots make perfect sense for ocean exploration because humans can’t operate there without a lot of support infrastructure,” Hsieh says. “Same with space exploration. The way I like to think about robots is as tools that extend our reach and give us a richer view into this fascinating world.”

Hsieh’s research group programs teams of robots, from small groups up to large-scale swarms, for marine studies and exploration.

“We are interested in coordinating teams of robots to do useful tasks,” Hsieh says.

Though individual robots might be suited to some tasks, there are often benefits to using teams.

“The reason you want to work with more than one is because of the naturally built-in redundancy,” Hsieh says. “The hope is that if you’re clever about how they coordinate and cooperate as an entity, they can act as more than the sum of their parts.”

Groups of robots can be useful in many situations where multiple spaces need to be monitored or explored at once, such as surveying the safety of rooms in a building after a fire before first responders go in, or in the ocean, where robot teams can help answer environmental questions.

“It’s such a big space that you can’t take one point measurement and say something about the entire ocean,” Hsieh says, “so it makes sense to use a large team of robots. For example, people are interested in studying coral bleaching. To do this, you have to monitor the health of the reefs, which means you have to look at the entire reef, not just certain spots.”

Hsieh uses tools from fluid mechanics and dynamical systems theory to model and program how teams of robots can work together to achieve a goal. Her work considers the many complications and constraints that arise in trying to get a team to work together — in or out of the seas.

“A good example is Amazon warehouses,” Hsieh says. “At the high level, the robots are all doing the same thing, so you really get the benefit of having more than one. But at the same time, there are new challenges. You can’t let them run into each other, and you have to make sure the workload is spread out so no one is doing the robot equivalent of twiddling their thumbs.”

Each different environment has its own considerations. Things would change, for instance, if the robots were searching the woods rather than working in a warehouse. “Natural environments introduce a new layer of complexity. Engineered things are predictable because they tend to have a set of rules everyone abides, but if you’re out in the ocean or in a forest, things are more challenging because there’s a lack of structure,” Hsieh says.

Marine environments present their own set of challenges. For one, the environment affects the robots. This wasn’t always an issue, says Hsieh.

“Historically, robots were massive things,” Hsieh says. “It was important that the robot didn’t punch a hole in the wall or send a human flying. It was all about making sure the robot did what it was supposed to do without causing any harm. Now, as robots get smaller, the way they move is more impacted by forces in the environment. When you’re big, the wind can blow on you and nothing happens. When you’re small, a wind gust can blow you off course. I’m interested in that connection — how does the environment interact with the robot?”

Fortunately, these forces aren’t necessarily a problem. In fact, one of Hsieh’s main interests lies in using those forces to the robots’ advantage.

“In one of our projects, we are thinking about how to plan energy-efficient trajectories for marine vehicles that leverage the flow of the water,” Hsieh says. If you have mapped out the locations of ocean features, such as sinks or high-current regions, you could plan the robots’ trajectory to use that naturally occurring flow. “How do you leverage flow to make sure you stay in one region, or go between regions to get the measurements you want?”

Conversely, in the water, the presence of the robots also changes the way the water moves.

“For ocean monitoring, we also need to consider how the vehicles deform the water around them as they take measurements, and how that impacts the measurements,” Hsieh says. “One of our projects delves more deeply into that interaction. The idea is that if we understand it, we can do a better job of getting vehicles to navigate and cooperate effectively.”

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