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Author Topic: Alternative motor ideas  (Read 1230 times)

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Offline SamcatTopic starter

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Alternative motor ideas
« 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?

Offline blackbeard

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Re: Alternative motor ideas
« Reply #1 on: September 03, 2010, 03:30:44 PM »
give it a shot. it'll probably use less power then a servo.
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Offline SamcatTopic starter

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Re: Alternative motor ideas
« Reply #2 on: September 03, 2010, 05:52:38 PM »
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.

Offline voyager2

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Re: Alternative motor ideas
« Reply #3 on: September 03, 2010, 06:32:08 PM »
How big are your magnets, and where did you get them?
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Offline SamcatTopic starter

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Re: Alternative motor ideas
« Reply #4 on: September 03, 2010, 08:39:04 PM »
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.

Offline voyager2

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Re: Alternative motor ideas
« Reply #5 on: September 03, 2010, 10:38:48 PM »
No I mean the electro magnets
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Offline SamcatTopic starter

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Re: Alternative motor ideas
« Reply #6 on: September 03, 2010, 11:04:24 PM »
 ;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.)

Offline voyager2

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Re: Alternative motor ideas
« Reply #7 on: September 03, 2010, 11:33:26 PM »
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
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Offline Soeren

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Re: Alternative motor ideas
« Reply #8 on: September 06, 2010, 04:08:04 PM »
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.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline SamcatTopic starter

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Re: Alternative motor ideas
« Reply #9 on: September 07, 2010, 09:04:45 AM »
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.
« Last Edit: September 07, 2010, 03:51:51 PM by Samcat »

Offline SamcatTopic starter

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Re: Alternative motor ideas
« Reply #10 on: September 07, 2010, 09:47:19 AM »
fixed?
« Last Edit: September 07, 2010, 03:52:18 PM by Samcat »

 


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