Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: Samcat on September 03, 2010, 03:07:24 PM
-
Greetings.
I am planning a small walker robot. The action of the legs is giving me fits. I want to have independent control of the x and y-axis of the legs. This cannot be done with independent servos or linear actuator, they are simply too large.
I came up with a solution, but i would like your feedback on it.
Here is a bad ASCII image of it.
Perm Mag Electromag Perm Mag
_______________________________
_______|___{} [|||||||||||] {}________|_____
|o | {} [|||||||||||] {} | o| fixed points for string routing
| ----------------------------------- |
| NS SN |
| o |
|o \ o|
--------------------------\-----------------------
string/fishing wire \
\ robot leg
\
------> \
motion \
The 'motor' would all be encased in something very thin, on the order of a straw. When controlling the electromagnet, it will cause the permanent magnets to pull the robot leg left/right, or up/down. This would be 12 separate motors (6 legs), but packaging would be greatly reduced and by using string for 'tendons' they could be strategically hidden..
In theory, you can move a leg in any path you want just be controlling the electromagnet voltage (analog output). Or use fixed voltages for just forward and back.
Like I said, I have not worked on it enough to know what is best sizing (length/width or straw), heat considerations, etc. Also need to decide how best to get the AC/DC power right to control both directions.
Has anyone else done any work like this?
-
give it a shot. it'll probably use less power then a servo.
-
I am waiting new magnets to show up (got the wrong type). I don't really have the right equipment to test efficiencies and find an optimal setup.
Just fishing for ideas while I am waiting.
-
How big are your magnets, and where did you get them?
-
http://www.kjmagnetics.com/proddetail.asp?prod=R412 (http://www.kjmagnetics.com/proddetail.asp?prod=R412)
Neodynium Ring Magnet N42
1/4" OD (should fit nicely inside a McDonald's straw)
1/16" ID (small enough to tie a string)
1/8" thick (needs to be large enough to not flip inside the chamber)
Ordered today. Should get in a few days.
-
No I mean the electro magnets
-
;D
I just made my own.
I started with a simple finishing nail, added some plastic washers I cutout (about 1/4" round), and wound magnet wire around it until it was the same height as the washers. I made a few of them with longer spans (from 3/8" to 3/4") and larger/smaller nails.
I did order some 1008 low carbon steel wire to use as the metal core to eliminate residual magnetism.
(how do you post pics? I can upload a few pictures of my horrible wrap job.)
-
To post pics:
[img][/img]Put the link to your pic in between the img bits
The picture has to be on the internet already, just upload it with something like photobucket.com
-
Hi,
Did you consider Muscle Wire?
If you have room elsewhere for servos/motors, you can use cable (like on a bicycle gear/brake) to transfer the movement.
-
Here is all of them
(http://i853.photobucket.com/albums/ab94/samcat604/AllEM.jpg)
The small ones detail
(http://i853.photobucket.com/albums/ab94/samcat604/SmallEM1.jpg)
The large ones detail
(http://i853.photobucket.com/albums/ab94/samcat604/LargeEM.jpg)
Fit into a straw
(http://i853.photobucket.com/albums/ab94/samcat604/InsertEM.jpg)
Obviously, I still need to cut the ends off the nails. But the nails have too much magnetic memory. I am afraid it will hurt performance of using them like an AC motor. I have ordered some low carbon steel wire to use instead.
I will investigate Muscle wire for the future. Figuring out the controls and cost will really complicate it. If the electromagnets don't work, I will take a closer look. For now, I want to get something off the ground.
-
fixed?