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This is completely flippant to say, since I've never built anything like this and don't understand the complexity behind it, but I'm surprised at how awkwardly

by spraak 9y ago

This is completely flippant to say, since I've never built anything like this and don't understand the complexity behind it, but I'm surprised at how awkwardly it looks swimming. It's clear to my eyes that it's not a real fish.

jonathanyc 9y ago
I wonder if other fish will interpret it as injured and attempt to eat it :)
- Mononokay 9y ago
  It's doubtful - it's swimming more powerfully than other fish, not less. It's why it looks so odd to humans - the tail strokes are far too heavy. Fish have a lot more subtlety in their own.
  - harperlee 9y ago
    But the fact that it spends more energy, and it is less efficient, should be interpreted as a sign that something is wrong, isn't it? The gestures are powerful but the fish does not advance a lot. Limping on one leg is a more extenuant exercise precisely because you need (and show) more power (and that is less sustainable). I don't think a lion would see it as a warning signal!
    - ibnjmn 9y ago
      I know next to nothing about submarine dynamics, but I am an RC plane pilot, and it looks to me like this fish swims in a constant stall. If it was a plane, I'd be inclined to say that its center of gravity was too far back. The video states that it can control its own bouyancy, yet it looks like it's constantly fighting to swim level instead of sinking. If it could achieve a neutral bouyancy then I bet it would glide along much more like a real fish.
harperlee 9y ago
I think the reason is that they tried to minimize the number of actuators (due to both dollar and energy costs), so more refined, undulating movements cannot be flexibly reproduced - instead, they are built-in in the hardware design.
kurthr 9y ago
Maybe it's intentional, but the tail looks much too heavy. It only looks remotely natural during transitions where it starts to dive. The motive tail is providing significant lift. As a later commenter (ibnjmn) mentions... it looks like the center of gravity is too far back. Maybe they designed this so that the robo-fish could stop quickly, but it certainly doesn't look efficient for something that is nominally neutrally buoyant.

by spraak 9y ago

jonathanyc 9y ago

I wonder if other fish will interpret it as injured and attempt to eat it :)

Mononokay 9y ago
It's doubtful - it's swimming more powerfully than other fish, not less. It's why it looks so odd to humans - the tail strokes are far too heavy. Fish have a lot more subtlety in their own.
- harperlee 9y ago
  But the fact that it spends more energy, and it is less efficient, should be interpreted as a sign that something is wrong, isn't it? The gestures are powerful but the fish does not advance a lot. Limping on one leg is a more extenuant exercise precisely because you need (and show) more power (and that is less sustainable). I don't think a lion would see it as a warning signal!
  - ibnjmn 9y ago
    I know next to nothing about submarine dynamics, but I am an RC plane pilot, and it looks to me like this fish swims in a constant stall. If it was a plane, I'd be inclined to say that its center of gravity was too far back. The video states that it can control its own bouyancy, yet it looks like it's constantly fighting to swim level instead of sinking. If it could achieve a neutral bouyancy then I bet it would glide along much more like a real fish.

harperlee 9y ago

I think the reason is that they tried to minimize the number of actuators (due to both dollar and energy costs), so more refined, undulating movements cannot be flexibly reproduced - instead, they are built-in in the hardware design.

kurthr 9y ago

Maybe it's intentional, but the tail looks much too heavy. It only looks remotely natural during transitions where it starts to dive. The motive tail is providing significant lift. As a later commenter (ibnjmn) mentions... it looks like the center of gravity is too far back. Maybe they designed this so that the robo-fish could stop quickly, but it certainly doesn't look efficient for something that is nominally neutrally buoyant.