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View Full Version : Tired of those tiny EX-106?



Xevel
10-10-2012, 09:14 PM
Looks like Robotis is moving up :)

http://www.youtube.com/watch?v=87yIr6QxX0w

J (http://www.youtube.com/watch?v=87yIr6QxX0w)udging by the shot where one is beside the CM-700, these are going to be pretty heavy duty stuff. :robotsurprised:

EDIT : they re-uploaded it in HD here http://www.youtube.com/watch?v=w_Hu7fN86tE

Th232
10-10-2012, 09:34 PM
Oh my...

That is terrifyingly awesome. Looks like the bolt patterns and so on will make them easier to work with than the current Dynamixels as well. Wonder what the specs will be.

tician
10-10-2012, 09:50 PM
Poorly judging from the zoomed image of the CM-700, it looks to be roughly the same cross-section as a NEMA 23 motor (maybe even a NEMA 17 for that smaller one). I wonder if the 'novel' gear reduction system is harmonic drive or something completely different (truly novel), assuming the cylindrical segment encapsulates the entirety of the gear system.

jwatte
10-11-2012, 12:15 AM
Technically, unless it's made by the Harmonic Drive companies, it's known as "strain wave gearing."

And, yes, I've been wanting to have some strain wave gears for servos for a long while, and been disappointed there really doesn't seem to be a low-cost supplier of the tech :-) So here's hoping.

Also: the video is "private."

Gertlex
10-11-2012, 12:22 AM
Aww. Guess I'm too late, as the vid has been removed.

Xevel
10-11-2012, 01:55 AM
They re-uploaded it in its full HD glory (http://www.youtube.com/watch?v=w_Hu7fN86tE), and as far as I can tell this one is not private (the first one wasn't either when I saw it...).

Xevel
10-11-2012, 02:12 AM
There is a few seconds where we see a test app running.
It says 24.1V, 5.6A for 31.9 N.m(=326kg.cm), 22.4RPM.

I'm not an expert, but this seems to be quite powerful.

jwatte
10-11-2012, 12:04 PM
32 Nm is huge! It's over 320 kgcm. It's at a low RPM, but still moving, so, great!
The only thing I see missing is a rear/opposed axle ;-)

jnugen
10-13-2012, 01:35 PM
My guess for the 'novel' gear system is a Hypocycloid Gear Reducer:

http://www.zincland.com/hypocycloid

-James Nugen

tician
10-13-2012, 09:56 PM
Cycloidal drives (http://en.wikipedia.org/wiki/Cycloidal_drive) supposedly are not back-drivable, so if the motor is able to move the horn to a given position then the motor must also move it away from that position. That usually spells trouble in robotics. Things often go wrong (electrical faults, user/programming errors, etc.) and being able to cut power to the servo and manually move the horn is essential to safety.

The new video cut out the side-by-side shot of one of the servos and a CM-700, but there are still two RX/EX sized servos (can't tell which) in gripper of the arm for a size comparison. In the mess of wires at ~26 seconds, I see independent 2-pin power (using T-connectors) and a 4-pin connection (wrapped in plastic coil wire conduit). I wonder if they were upgraded to full-duplex RS-485, or even if they maybe separated motor power (2-pin) from the control board power and comms (4-pin).

For a torque comparison, a banebots P60 gearbox maxes out at 35 [lbf-ft] (~484 [kg-cm]) and a P80 gearbox maxes out at 85 [lbf-ft] (~1177 [kg-cm]).

Th232
10-17-2012, 07:33 PM
And now the specs are up:
http://blog.trossenrobotics.com/2012/10/17/dynamixel-pro-specs/
http://www.robotis.com/xe/?mid=DynamixelPro_en

24V looks good, check out the power consumption! Bit on the slow side, but given the size and power, can't really complain about that.

tician
10-17-2012, 08:31 PM
Huh. It does use cycloidal reduction gearing. Fancy that. They're also quite a bit smaller than I was thinking.