Alternative motor ideas

[Samcat]

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?

[blackbeard]

give it a shot. it'll probably use less power then a servo.

[Samcat]

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.

[voyager2]

How big are your magnets, and where did you get them?

[Samcat]

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.

[voyager2]

No I mean the electro magnets

[Samcat]

 

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.)

[voyager2]

To post pics:

Code: [Select]

[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

[Soeren]

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.

[Samcat]

Here is all of them


The small ones detail


The large ones detail


Fit into a straw


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.

[Samcat]

fixed?