Swimming Cockroach Robot Developed

Onnimikki writes "The Ambulatory Robotics Lab at McGill University has made a six-legged swimming cockroach robot as part of Project Aqua. The robot is a waterproof version of the RHex robot, whose inspiration is the biomimetic work by Bob Full of Gecko glue fame. Other cool stuff from the ARL page includes a waddling bipedal RHex, and the world's first galloping robot."

Buoyancy

[Rosco P. Coltrane]

waterproof version of RHex, which was made neutrally buoyant

How did they do that ? Depending on the density of the water you immerse the thing it, they might approach neutral buoyancy by adjusting the amount of ballast manually, but they'll never achieve true static buoyancy without some kind of active process controlling the amount of water in a ballast tank. Otherwise the object would sink to the bottom or bob up to the surface eventually. Or do they maintain the thing's depth in the water with dynamic buyoancy using the robot's forward movement ? I don't see depth control planes on the robot, could they use its legs to achieve this ?

Re:Fun

[lmfr]

hm? "/" means "or", doesn't it? ("or" as used in common language)

Re:Complicated much?

[Anonymous Coward]

It is too easy to program wheel-based robots. They seem to be used more frequently for following black lines on the ground, object avoidance, and following walls - things like that.

On the other hand, walking robots often have multiple servos at each leg. Thus, in order to take a few steps, it requires a complex progression of commands that cause each leg to lift, rotate forward, and so on.

loop thru legs 1 - 4
Shoulder servo: up 45 degrees
Elbow servo: up 30 degrees
end loop
loop thru legs 1 - 4
Have servos return to neutral position
end loop

All that just to take one step.

Once you have the basic walking mechanics down, you can invent different paces, gaits, and variations on the theme. You can use a controller chip such as the basic stamp to program all this stuff in (http://www.parallax.com).

Then, once you have defined 'walking' from a programmatic standpoint, you can use an RC adapter to send commands to the basic stamp, which interprets the signals as forward (run the embedded walk program we defined above), backward, etc. Much more interesting than rolling about!

Plus, alot of these robot guys have BattleMech fetishes. They won't quit until there are Ullers running around the lab.

Re:Buoyancy

[Zog The Undeniable]

OK for shallow depths, but as the robot gets compressed at greater depths, its volume decreases and it will sink faster and faster (like a submarine that blows too much air from its tanks). There are also problems with temperature change. There's an interesting passage in Lothar-Gunther Bucheim's book "Das Boot" (better known as a TV series and film) where the Chief Engineer explains the variable buoyancy problem caused by temperature, depth and varying salt concentrations to the narrator. The U-boat has to take on or lose a surprisingly large weight of water to compensate for even a 1 degree change in water temperature.

But I digress, I doubt there's much call for a deep-sea robot cockroach.

Re:Complicated much?

[Dr. Smeegee]

On a large machine that must pick it's way carefully through a delicate area, legs may be a decided advantage.

Scope ye the Plustech [plustech.fi] Harvester. It uses six hydraulicly actuated legs and a big-assed arm with a gripper/saw on the end to harvest trees from delicate areas.

Some guys I went to high school with use horses to harvest hardwoods from Indiana forests due to the trees inaccessability to wheeled vehicles.

Legs are useful!