Building Better Robots By Understanding the Physics of Walking Without Spilling Coffee

There’s a lot of subconscious calculations that keep the hot liquid inside the cup, as opposed to on our shirt and pants.

The barista hands you your morning coffee, black. “Thanks,” you say trying to keep your eyes from drooping closed. You check your phone for the time, and you realize you’ll need to speedwalk to make the job interview.

There’s a lot of complex adjustments that your brain makes so that the coffee doesn’t end up spilling.

You take a sip of the piping hot elixir, check that the lid is on tight, and carefully keep the brew safe as you rush to the interview. While you might be worried about a hundred different things, none of them including keeping your coffee cup balanced.

Humans are really good at keeping the liquid from sloshing out. There’s a lot of complex adjustments that your brain makes so that the coffee doesn’t end up spilling. But while these adjustments are second nature to us, designing robotic arms and machines that automatically rebalance objects is quite challenging.

Physicists from Arizona State University published a study in the scientific journal called Physical Review Applied which described the physics of balancing coffee while walking. Professor Ying-Cheng Lai, corresponding author of the study explained:

“While humans possess a natural, or gifted, ability to interact with complex objects, our understanding of those interactions — especially at a quantitative level, is next to zero.”

To mimic the motion, the researchers examined how participants manipulated a cup with a rolling ball inside as they moved. This simulated the experience of walking with coffee without the risk of spilling it on themselves.

Researchers found that humans were really good at switching between different types of motion when adjusting for both the sloshing motion and the horizontal movement. The challenge will be mimicking these adaptations and flexibility in robots that struggle with this complex motion. Understanding the underlying physics might be key for developing new robots and prosthetics.

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