Society of Robots - Robot Forum

Mechanics and Construction => Mechanics and Construction => Topic started by: kinderbot on January 14, 2009, 02:10:15 AM

Title: quietest, smoothest actuators for robot arm?
Post by: kinderbot on January 14, 2009, 02:10:15 AM

I'm working on a life-sized, anthropomorphic, 6-DoF arm and I'm in need of some serious muscle.  Nitinol is too weak for this application, and most of the other actuators I've seen (air muscle, servos, steppers, pneumatic pistons, etc.) are either too weak, too noisy, too jerky, or a combination of those.  I need something smooth and almost silent in operation that can still deliver a significant amount of torque -- and quickly -- yet can fit within the relatively small space of the enclosure.

The two options that come to mind for the pivoting joints are hydraulic impellers, and hydraulic pistons or electromagnetic solenoids.  For the rotational joints, I'm thinking of opposing pairs of electromagnetic solenoids.  But I'm probably blanking on other possibilities.  Any suggestions?

Title: Re: quietest, smoothest actuators for robot arm?
Post by: bryan922 on January 14, 2009, 12:54:38 PM

The MIT robotics department is recently using voice coil linear actuators because they are silent, have variable speed, only one moving part, no gears and are back drivable, which means that an opposing force does not harm it.

Here is a video of what a voice coil looks like in operation:

http://www.youtube.com/watch?v=nDl_sbHNVss

Here is the MIT page which discusses them:

http://robotic.media.mit.edu/projects/hardware/actuators/overview/overview.html

Here is more information on the various MIT robots:

http://robotic.media.mit.edu/index.html

Title: Re: quietest, smoothest actuators for robot arm?
Post by: kinderbot on January 14, 2009, 01:13:56 PM

Thank you!  That's great information that I've never seen before.

Quote from: bryan922 on January 14, 2009, 12:54:38 PM

The MIT robotics department is recently using voice coil linear actuators because they are silent, have variable speed, only one moving part, no gears and are back drivable, which means that an opposing force does not harm it.

Here is a video of what a voice coil looks like in operation:

http://www.youtube.com/watch?v=nDl_sbHNVss

Here is the MIT page which discusses them:

http://robotic.media.mit.edu/projects/hardware/actuators/overview/overview.html

Here is more information on the various MIT robots:

http://robotic.media.mit.edu/index.html

Title: Re: quietest, smoothest actuators for robot arm?
Post by: bryan922 on January 14, 2009, 01:22:30 PM

Yes, it is great information. Now, good luck on finding a source for them. I found three manufacturers, but no indication on how to buy them or what their price is. But I am very interested. Let me know if you find anything out.

Also, please don't confuse these things with the screw type linear acutators that are slow, and have gearing, and which you see mentioned from time to time around here.

The voice coils are literally just a copper winding around a tube, and the tube resides around a core and inside a shell.

Here are some manufacturers:

http://www.moticont.com/voice-coil-motor.htm

http://www.beikimco.com/actuators_linear.php

http://www.h2wtech.com/noncommdcactu.htm

They are also used in speakers, and every hard drive has a small one inside it.

Title: Re: quietest, smoothest actuators for robot arm?
Post by: Admin on January 27, 2009, 12:23:16 AM

Can you tell us more about the arm you are trying to design? Expected speeds, torque, weights, size, etc?

(very important when selecting actuators ;D)