Robot Designed to Move Like a Knifefish


(Video Link)


Knifefish have a long doral fin that flutters back and forth to move the fish. Here's a video showing one in motion. Scientists at Northwestern University thought that it could serve as a useful basis for an underwater robot, and so studied its movement:

Planning for the robot -- called GhostBot -- began when graduate student Oscar Curet, a co-author of the paper, observed a knifefish suddenly moving vertically in a tank in MacIver's lab.

"We had only tracked it horizontally before," said MacIver, a recent recipient of the prestigious Presidential Early Career Award for Scientists and Engineers. "We thought, 'How could it be doing this?'"

Further observations revealed that while the fish only uses one traveling wave along the fin during horizontal motion (forward or backward depending on the direction on the wave), while moving vertically it uses two waves. One of these moves from head to tail, and the other moves tail to head. The two waves collide and stop at the center of the fin.


The researchers then created a computer simulation of the fish and designed a robot to duplicate its movements:

The group took the robot to Harvard University to test it in a flow tunnel in the lab of George V. Lauder, professor of ichthyology and co-author of the paper. The team measured the flow around the robotic fish by placing reflective particles in the water, then shining a laser sheet into the water. That allowed them to track the flow of the water by watching the particles, and the test showed the water flowing around the biomimetic robot just as computer simulations predicted it would.

"It worked perfectly the first time," MacIver said. "We high-fived. We had the robot in the real world being pushed by real forces."


Link via Fast Company

Comments (3)

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The way these fish swim is interesting, but the most fascinating thing is that they can sense electric fields around their bodies:

http://www.hizook.com/blog/2010/01/14/bode-plots-fish-awesome-electric-field-sensing-fish

(RE: the above link, how cool is it that they've made Bode plots of the fish's motion? That's something any good engineer can appreciate!)

This same form of sensing has been used by other robots; for example, here is a robot using electric field sensing to plug itself into wall outlets for automatic recharging:

http://www.hizook.com/blog/2010/01/03/self-feeding-robots-robots-plug-themselves-wall-outlets
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...So.... Is this why .... how shall I put this Deilcately..... ehhhhhhhh..... she .... well...., looks like she clearly appreciates her own cooking.......?

...Oh I'm sorry- She has to feed 120 persons and this is just a small part of the dish...!!!

:lol:
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This is why your fat!!!

I watched her make the dressing I keep thinking "How much salad are you making?" That amount of dressing is for 4-6 pounds of cooked pasta not one.
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This made me so incredibly sad. I was hungry but now I think I'll go walk around the block. The internet was MADE for someone like her to make friends, why on earth would she put up a video?! I'm so confused.
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WTH was the point in pointing out the calories. It's not like an average person is going to sit down and eat the entire bowl.
Anyway, it looked disgusting. WAY too much dressing. It looked like macaroni soup in the end, bleh.

As for the woman.... Just makes me feel bad for her. She was just standing there and she had to struggle for breathe.
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So let's say, at a bbq, this will feed 12 people as a side dish. That's still over 500 calories per serving.

Next time I feel like something "sweet, but with a tang" I'll go straight for the Sour Patch Kids, thx. There's less than 200 calories in a bag of 'em, and no fat.
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Speaking as someone from the South, this is how we were taught to eat. Paula Deen isn't that much better. I've struggled with my weight all my life and it's because of bad food choices, but it was all I knew. I've lost 60 lbs since March and I can't imagine eating the old way ever again.
Now, also speaking as a Respiratory Therapist who works in the ICU, I'll be seeing 'Simply Sara' very soon..:(
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That POOR WOMAN. Yes, that's how many Americans were taught to eat... and look how enormous it's made this young woman, who seems very sweet. Agreed, if this were made with yogurt and/or low-fat mayonnaise it would be just fine. Maybe someone should send her a hint so she can live to 30. And I'm going to go throw out those cookies I just bought.

Moderator, were you thinking of macaroni and cheese? I have never had macaroni salad with cheese in it.
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@Feh - I probably did confuse the terminology re mac and cheese, because what she was making is what I would have termed "pasta salad." I've modified the post accordingly. Tx.
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I once worked with a woman whose mother-in-law was the size of this girl. My coworker told me that her mother-in-law would melt a stick of real butter in a pan and fry a pound of bacon in it. Well at least she didn't have to worry about the bacon sticking to the pan. In my experience a lot of people from the south and rural areas were just brought up to believe that this type of cooking is wholesome and nutritious.
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To be honest I don't really see how this is 'neat'. I get that it might be funny to some, but really it just makes me feel awful...It's not really instructional and wasn't at all interesting to me, making me wonder why it was posted in the first place? To poke fun at some poor hugely overweight woman? I can't see how else it is relevant.
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@Lauren - I was the one who posted this item, and the point you make was at the forefront of my mind as I did so. I can absolutely guarantee that there was no intention to mock the lady's obesity per se. I considered specifically asking readers not to make hateful comments about the lady herself (and I'm pleased to note that the typical reply is one of "sadness" rather than something derogatory of her body habitus). Editorial control allows the author to delete selected comments, so I thought in that regard that it was safe to post the item.

With regard to the "neatness" of the subject matter, what the video demonstrates - once you get beyond the initial "yuck" factor - is how inadequate knowledge (or poor choices) in the kitchen can lead to frankly dangerous food concoctions. The audience for this blog is on the whole sufficiently sophisticated that such "instructions" may be superfluous, but I would hope that there are some readers (who perhaps didn't comment) who may have some second thoughts about their culinary maneuvers as a result of seeing this video.
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I can see how maybe it can be used as a tool to make us all questions what we do eat and how dangerous those choices can be, but it seems to be in slightly poor taste to do so in this way. I think the point would have been clear had anyone made such a salad, let alone to have those extra comments on top regarding the nutrition (though it was relevant and shocking) as well as the unfortunate lady doing the cooking. It seems to be a rather cruel way of making us re-evaluate out eating habits, insofar as it relies most on our shock/disgust/pity for the lady cooking more than anything else.

Yet, I am also glad to see that most of the comments have been thoughtful and relevant and as you pointed out, reflect that many of this find this saddening rather than humorous. I just imagined that had I been in the place of the creator of that video I don't think I'd want to be used as an example of what not to do, regardless of how unhealthy my cooking was. Sorry if I came across as too preachy, it's more the fact that I find the video a upsetting because it portrays the way some people cook and their lack of nutritional knowledge etc., which isn't an isolated thing by any means, but does so at the expense of this lady. Granted, she put the video up the first place, but that is also a bit saddening as she obviously didn't see the connections people would make...

Anyway, thanks for the thoughtful reply. :)
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I'm probably on the extreme reverse side of this. Being on a restricted calorie diet and a bit of a mad scientist I make it an obsesssion to see how may calories I can cut, while still making something fairly tasty/edible (kinda like Hungry girl, if you've ever heard of that website.)
My Fauxato salad (for a cup ie 8oz serving) that I make runs you about 48 calories and tastes awesome. :)
Now... if only Shiritake would come out with macaroni shaped yam noodles, I could do some awesome mac salad.

Now, in the poor girls defense, I doubt one serving is the whole bowl. Eyeballing that, I'd say there could reasonably be 12-16 servings. So... 425 -567'ish calories. While very high still, its not that far off from commercial macaroni salad.
Resers (a store-bought brand) mac salad has 320 calories for a serving. And they claim a serving is 3/4'ths of a cup.
If anything this vid should make you aware of what goes into that crap (even commercial brands). Anything coated in mayo or dressing should really be avoided.
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vegtables aren't crunchy after they've been soaking in fat for a while. Jeeze, sweet and tangy, how about fat and caloric. The vinegar and maybe one spoonful of light mayo would be a great dressing for a pasta salad. But sugar AND condensed milk? I'm sorry but I think i'd go into a diabetic coma after eating that.
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wow, if this is how some people were shown to eat food...well i just can't believe it! i think a lot more thought should be put into educating people on how to eat healthily because this is just simply not right.
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