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Anyone know a good design for an array of interlocking linear actuators

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jpoopdog

Mon Nov 05 2012, 12:00AM

Registered Member #6188 Joined: Wed Aug 15 2012, 08:34AM
Location:
Posts: 23

Hi,

Recently i was inspired to try and create something that would emulate muscle movement, a linear actuator, however, solenoids can only pull over a very short distance, so i want to design an array which interlock and overal contract to the shortest possible length without sacrificing too much pulling power.

What i plan on doing is create many solenoids with parts that connect each other, such as a metal rod on the front of each solenoid and a hole in the back, though im not sure exactly how much extra magnetism the rod will conduct or how it will shape the magnetic feild, and how it will affect the magnetic pull. Does anyone know a good design for what im trying to acheive? maximum linear contraction with minimal loss of power at a high speed, if not, how would i go about working out exactly how to get the most pull over a longer distance?

I am willing to put in the time and effort to hand build hundreds of small solenoids and cores to any design, whatever it takes.

Marko

Mon Nov 05 2012, 04:21AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi

Your solution may be a linear stepper motor

You just need to find a way to miniaturize it into a flexible fiber and bundle many of them together to emulate a muscle

I contemplated that the "stator" may be a thin flexible steel tube with teeth inside, and the "rotor" would be a toothed wire sliding inside it. It's hard to picture, but you'd also need to have two thin long coils built into each fiber to produce stepper action.

Not something that could be built at home, but you could probably build a supersized version as a demonstration!

Marko

Sulaiman

Mon Nov 05 2012, 06:08AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

How about solenoids with a large pulling force using pulleys to exchange force for distance
... like the pulley system on a hoist/crane but in reverse?
e.g.

Pinky's Brain

Mon Nov 05 2012, 08:44AM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

Or a concertina type extending grating, like those toy boxing gloves.

PS. what does this have to do with radiation?

Steve Conner

Mon Nov 05 2012, 12:20PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

This is the neatest emulation of muscle movement I've seen. There's a similar thing that works by heating nitinol "shape memory" wire.

Sulaiman

Mon Nov 05 2012, 02:11PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Thinking about it ....
a stepper motor winding the pull-wire around it's shaft is probably the cheapest/easiest way to achieve controlled significant linear motion.

jpoopdog

Tue Nov 06 2012, 10:33AM

Registered Member #6188 Joined: Wed Aug 15 2012, 08:34AM
Location:
Posts: 23

Its also the slowest method which is specifically why im not doing it.
Ive looked at every alternative method, and solenoids beats them all in everything but power to force efficiency and precision , the latter being the main reason they arent used as much as others.

I dont think i was able to accurately explain what i am trying to acheive, so ive attached a rough sketch of an example
im looking for whatever will allow the greatest pull force along with the highest possible amount of contraction, using either solenoids, electromagnets or both like ive done in my sketch. i dont know what the most effective way to go is when dealing with numerous solenoids, electromagnets can pull much harder than solenoids over a short distance, wheras solenoids work at a slightly longer distance thus the pull force is spread across that area. Im just not sure which is the best way to go, also considering space, although i could put a few solenoids together, i could build a hundred electromagnets and use them in the same space. im also not sure how effective using solenoids with interlocking cores (as in my sketch) would work.

1352197985 6188 FT146090 Solenoid Array Idea

Shrad

Tue Nov 06 2012, 01:13PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

pneumatic is the route to go

you wont need a super duper compressor to get decent force (a small car AC one would do) plus you can put the compressor at any place you want in your device

Sulaiman

Tue Nov 06 2012, 01:15PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Is this open-loop or do you intend to have position or force feedback?

Dr. Slack

Tue Nov 06 2012, 02:56PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Yes, solenoids are pretty quick, until you start stacking them in series. Instead of just accelerating the mass of a small amarture, you're accelerating the mass of several solenoids. Not only that, the more remote ones are accelerated to a higher speed, so your "mechnical impedance" is going as N squared, where you have N stacked solenoids. The maths is much the same as for multi-stage Marx and C-W high voltage generators.

For power to weight ratio, you want the big burly cousin of the stepper motor that Sulaiman mentioned, the brushless DC motor, driven by a sensored ESC, so you can operate down to zero rotational speed.

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