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posted by janrinok on Friday September 10, @02:15AM   Printer-friendly
from the rock-and-roll dept.

Walking with coffee is a little-understood feat of physics: Understanding the physics behind natural processes provides new applications for soft robotics, manufacturing automation:

The coffee, a thermally agitated fluid contained in a cup, has internal degrees of freedom that interact with the cup which, in turn, interacts with the human carrier.

"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," said ASU Professor Ying-Cheng Lai, an Arizona State University electrical engineering professor. "We have no conscious ability to analyze the influences of external factors, like noise or climate, on our interactions."

Yet, understanding these external factors is a fundamental issue in applied fields such as soft robotics.

"For example, in design of smart prosthetics, it is becoming increasingly important to build in natural modes of flexibility that mimic the natural motion of human limbs," said Brent Wallace, a former undergraduate student of Lai's and now a doctoral student in ASU's Ira A. Fulton Schools of Engineering. "Such improvements make the prosthetic feel more comfortable and natural to the user."

According to Lai, it is conceivable that, in the not-too-distant future, robots will be deployed in various applications of complex object handing or control which require the kind of coordination and movement control that humans do quite well.

If a robot is designed to walk with a relatively short stride length, then relatively large variations in the frequency of walking are allowed. However, if a longer stride is desired, then the walking frequency should be selected carefully.

A new paper published in Physical Review Applied, "Synchronous Transition in Complex Object Control," originated with Wallace as part of his senior design project in electrical engineering, supervised by Lai. Wallace has received an NSF Graduate Fellowship and now is a doctoral student in ASU's School of Electrical, Computer and Energy Engineering.

The ASU team's research expands on a ground-breaking, virtual experimental study recently conducted by researchers at Northeastern University, using the coffee-cup-holding paradigm and adding a rolling ball, to examine how humans manipulate a complex object. Participants deliberately rotated the cup in a rhythmic manner with the ability to vary force and frequency to ensure the ball stayed contained.

The Northeastern study showed that the participants tend to select either a low-frequency or a high-frequency strategy -- rhythmic motion of the cup -- to handle a complex object.

A remarkable finding was that when a low-frequency strategy was used, the oscillations exhibit in-phase synchronization, but antiphase synchronization arises when a high-frequency strategy was employed.

Journal Reference:
Brent Wallace, Ling-Wei Kong, Armando Rodriguez, et al. Synchronous Transition in Complex Object Control, Physical Review Applied (DOI: 10.1103/PhysRevApplied.16.034012)


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  • (Score: 4, Interesting) by Rosco P. Coltrane on Friday September 10, @03:35AM (6 children)

    by Rosco P. Coltrane (4757) on Friday September 10, @03:35AM (#1176485)

    This is quite well known: if you hold a cup of coffee while walking and the liquid starts to move and is about to spill over, immediately change the pace of your stride and it'll stop. You have to catch it quick though, because as soon as it enters resonance, it goes fast.

    My personal habit is to grab the cup from the coffee machine and watch it for the first 2 or 3 steps. If the coffee inside the cup stays more or less still, I just keep walking at that pace and never look at it again.

    Also, keep your arm loose to decouple the cup from your body's movements as much as possible. I.e. turn your arm into a kind of steadycam mount.

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  • (Score: 0) by Anonymous Coward on Friday September 10, @11:49AM (3 children)

    by Anonymous Coward on Friday September 10, @11:49AM (#1176566)

    Reducing interference effects helps, but more generally just isolation. When I ealkwith xoffee, the coffee has a trajectory in space, and I fit myself underneath and around the coffee.

    Same as shooting on the move or a spoon and egg rest. You isolate that limb, and yout brain does the inverse kinematics to put you in place below it.

    • (Score: 0) by Anonymous Coward on Friday September 10, @11:52AM (2 children)

      by Anonymous Coward on Friday September 10, @11:52AM (#1176567)
      I should mention, the same is also taught to fencers. You move with your head "hanging" from a rail so the foil and your movement is smooth and quick.
      • (Score: 0) by Anonymous Coward on Friday September 10, @03:48PM (1 child)

        by Anonymous Coward on Friday September 10, @03:48PM (#1176662)

        Funny similar thing. When I started practicing aikido, I stopped spilling coffee when walking. When one part of your body is held, you train to (mostly) surrender it and consider it already immobilized. You're up against someone stronger than you, after all. Then move the rest of your body around that point. I guess I'm pretending the coffee is holding me? or something.

        • (Score: 0) by Anonymous Coward on Friday September 10, @08:43PM

          by Anonymous Coward on Friday September 10, @08:43PM (#1176793)

          Cubert J. Farnsworth : I understand how the engines work now. It came to me in a dream. The engines don't move the ship at all. The ship stays where it is, and the engines move the universe around it.

  • (Score: 2) by everdred on Friday September 10, @03:40PM

    by everdred (110) Subscriber Badge on Friday September 10, @03:40PM (#1176657) Homepage Journal

    turn your arm into a kind of steadycam mount

    This is the exact metaphor I've used when trying to explain how to securely hold a cup of coffee as a passenger in a car. If you tense up as the car goes over a bump you just transmit the shock. And for a full cup, you're better off with a loose arm than a cupholder.

  • (Score: 0) by Anonymous Coward on Friday September 10, @09:24PM

    by Anonymous Coward on Friday September 10, @09:24PM (#1176799)

    Also, keep your arm loose to decouple the cup from your body's movements as much as possible. I.e. turn your arm into a kind of steadycam mount.

    I find it's best to hold the cup in your non-dominant hand, so in your left hand if you're right-handed.