How to make air muscles!

I needed to create some actuators for an animatronics project I'm working on. Air muscles are very powerful actuators that work very similar to a human muscle and have a phenomenal strength to weight ratio- they can exert a pulling force up to 400 times their own weight. They will work when twisted or bent and can work under water. They're also easy and cheap to make!

Air muscles (also known as a McKibben artificial muscle or braided pneumatic actuators) were originally developed by J.L. McKibben in the 1950's as an orthotic appliance for polio patients.

Here's how they work:

The muscle consists of a rubber tube (bladder or core) that is surrounded by a tubular braided fiber mesh sleeve. When the bladder is inflated the mesh expands radially and contracts axially (since the mesh fibers are inextensible), shortening the overall length of the muscle and subsequently producing a pulling force.

Air muscles have performance characteristics very similar to human muscles- the force exerted decreases as the muscle contracts. This is due to the change in the interweave angle of the braided mesh as the muscle contracts- as the mesh expands radially in a scissors like motion it exerts less force due to the weave angle becoming increasingly shallow as the muscle contracts (see the diagram below- figure A shows that the muscle will contract to a greater degree than figure C given an equal increase in bladder pressure).The videos show this effect as well. Air muscles can contract up to 40% of their length, depending on the method and materials of their construction.

Gas law states that if you increase pressure you also increase the volume of an expandable cylinder (provided temperature is constant.) The expanding volume of the bladder is ultimately constrained by the physical properties of the braided mesh sleeve so in order to create a greater pulling force you need to be able to increase the effective volume of the bladder- the pulling force of the muscle is a function of the length and diameter of the muscle as well as its ability to contract due to the properties of the mesh sleeve (construction material, number of fibers, interweave angle) and bladder material.

I constructed two different sized muscles using similar materials to demonstrate this principle- they both were operated at the same air pressure (60psi) but had different diameters and lengths. The small muscle really starts to struggle when some weight is put on it while the larger muscle has no problems at all.

Here are a couple of videos showing both of the constructed air muscles in action.

Now let's go make some muscles!

Step 1: Materials

All of the materials are readily available on Amazon.com, with the exception of the 3/8" braided nylon mesh- it is available from electronics suppliers. Amazon does sell a braided sleeving kit with several sizes of braided mesh but the exact material is not stated-
Amazon

You'll need an air source:
I used a small air tank with a pressure regulator but you can also use a bicycle air pump (you will have to make an adapter to make it work with the 1/4" poly hose.
Air tank- Amazon
Pressure regulator (will require a 1/8" NPT female to 1/4" NPT male adapter)- Amazon

1/4" high pressure poly tubing- Amazon
multitool (screwdriver, scissors, pliers, wire cutters)- Amazon
lighter

for the small muscle:
1/4" silicone or latex tubing- Amazon
3/8" braided nylon mesh sleeve (see above)
1/8" small hose barb (brass or nylon)- Amazon
small bolt (10-24 thread by 3/8 in length works well)- Amazon
steel safety wire- Amazon

for the large muscle:
3/8" silicone or latex tubing- Amazon
1/2" braided nylon mesh sleeve- Amazon
1/8" or similar sized drill bit- Amazon
21/64" drill bit- Amazon
1/8" x 27 NPT tap- Amazon
1/8" hose barb x 1/8" pipe thread adapter- Amazon
small hose clamps- Amazon
3/4" aluminum or plastic rod to construct the muscle ends- Amazon

Safety note- make sure you wear safety glasses when testing your air muscles! A high pressure hose that pops off a loose fitting could cause a serious injury!

Comments

[ExoFOX]

im building the iron man suit obvsly minus anything power by the fictional arc reactor , any tips or comment are welcome , just looking to talk and make sum friends in the process of this exp,......thank you all

[Honus]

I'm currently working on a full animatronic Iron Man suit for a friend so I'll have a complete instructable up when it's finished. Everything is powered by servos though- no air muscles.

[ExoFOX]

thats whats up i would like to see the process of your exp' i myself am using linear force and gravity to make mines work sum hydrolics or shock obsobvers but not batteries,

[ExoFOX]

im using old technology like the pharros back in egypt days meaning i wount be using battery i am using motors but not run on batteries or liquids just motion and pure physics

[Ghunter10]

i remember seeing this instructable when it was first shown in the email send out as a featured ible and i favorited it, i have now come back and am designing a "gauntlet" that someone puts their arm into and the muscle will hopefully add to the strength of their motion, thank you for the inspiration.

[Honus]

That sounds like a really cool project- make sure to post pics or video when it's done!

[Ghunter10]

here is what i have so far for a design for a bicep, what do you think?

[mikecharlie]

Hey just spotted this and thought it would be really cool if you could do this, but if you use this for an exoskeleton then note that the air muscles can fail and cause a lot of pain, trust me if done something like this and couldnt bear the pain it gave me, when it collapsed it had caused a metal 'pinch' and fractured my arm. Just watch out for that but good luck with the attempts. :)

[pharseid]

I think it needs a rotational joint at the elbow. And the cables should be attached to a disk or something to translate the contraction of the muscle into torque.

If this works out, do you plan to extend the exoskeleton to more body parts? I just read Wearable Robots: Biomechatronic Exoskeletons and I suppose I'm interested in working on the same sort of thing. Also, I just found this website, are other people here working on exoskeletons?

[Ghunter10]

I would love to turn this into an exoskeleton (and hope to), the problem I' ve had is cost so far, so a decent amount of time is taken saving up for the different parts.

[pharseid]

You should enter the Jack Daniel's contest. $25,000 would buy a lot of parts.

[Honus]

That looks pretty interesting- how exactly will it work?

[Ghunter10]

i intend to have the system set up where a button operated valve will be on the ring in the bottom left of the picture set up where it faces downward towards the arm inside. when the arm flexes the valve will open and provide air for the air muscles (depicted as black cylinders) which would contract, as they contract cables attached to the muscles and the ring with the valves would hopefully pull the arm up into a flexed position, i then need to design another system on this that would involve more muscles that will create the opposite motion to bring the arm and frame back down.

[strongbino]

In order to decrease the weight of the system, can the air compressor only be used in the initial filling of a muscle and then removed and then have the air flow into the adjacent muscle or another container and then the adjacent muscle?

[pharseid]

I would think that would complicate the valve system, one set of valves to prefill the muscle and the other set to take it to full pressure. Plus there's no guarantee that a muscle will need to deflate at the time another muscle needs to inflate. But if the muscles all deflated by releasing into a common line, you could put a compressor on that line which exhausts into the system's holding tank. The compressor would have to do less work when the air at the inlet was at higher than atmospheric pressure.

[Honus]

I don't know about that- I guess you would just have to try it and see.

[strongbino]

I just feel like its a waste to expel the air from the muscle into the atmosphere. It would be more efficient to have it circulate through the system to another muscle so that the pressure remains constant.

[jibblesmgee]

I want to scale this up a little. I had the idea of using sections of bicycle innertube, and finding a substitute for the nylon mesh (or just some heavy duty wide diameter nylon mesh) and seeing what I could do with it. Has anybody tried this? I'll let everyone know how it goes when I get around to it.

[Graceria]

I'm working on a set of animatronic angel wings and I need it to be entirely free of any showing tubes or wires and I need to be able to move freely without being attched to anything. These air muscles look like they could be the solution to a problem I've been having with the wings not looking natural enough. Could these be made using a small air canister with a limited supply of air and is there a way I could set it up so that the air would return to the canister when the muscles relax? I'm not quite sure how I could get the air moving the way I need it to.

[Honus]

Sorry for the late reply- been super busy! I think they would work really well for your application. You could make a small air tank from a plastic soda bottle (I think they're good to at least 60psi.) I'm not sure about the air return as I haven't yet done anything like that. The smaller muscles don't consume that much air so it might not be that big a problem unless you need it to go for several hours or over say fifty cycles. A lot of it is going to depend on your design.

[Tolderian]

Only a few years behind the times but... check out EARS... stands for (E)something (A)ir (R)eturn (S)ystem. Not sure how to incorporate it... but, that's why I'm telling you. Surely you, or someone on these sortsa pages, can come up with something for the common man. w00t!

[Graceria]

Thanks! I'll check that out!

[Honus]

Exhausted Air Return System is a really great idea- I'll have to do some research on that to see if it would work.

[Tolderian]

Well if you figure out a way to Macgyver it, that'd be pretty sweet.

I made a couple of the muscles that chewee threw up here that worked well but it just seems like an awful lot of wasted air that could be recycled and make any reserve tank last longer.

Just throwing that out there.

I come back along from year to year to see if anyone else has pooped another gem of amazing. First time I've ever posted. Good luck!

[kikiclint]

 as long as you have some kind of quiet pump, capable of the necessary psi, you could just have it continually fill the bladder, and just let a solenoid valve release the air.  Either that, or you will have to pump the air back from the muscle.  It wont be that important to recycle the air, unless you are in space. 

[nidobrito]

Hello i have a question.
How exactly the pressure regulator works with the air muscle?
I presume that when i turn the regulator for one side, the muscle contracts, when i turn to the oderside, releases the air inside it and relaxes.
It's correct?

[Honus]

That is correct.

[nidobrito]

So, like this image i posted, is the linkage correct? and if is correct, i just add a modified servo, so when turn servo the muscle contracts/relaxes.

[Honus]

Technically that is correct but I think you would have a difficult time making that work. Your best bet is to use a solenoid valve-
http://www.mcmaster.com/#air-solenoid-control-valves/=dpt784

[nidobrito]

Yeah i tried with the solenoid valves but "Mother of God!", even in ebay they are very expensive, do you know another solution for it, that can be electronically activated?

[Honus]

Have you tried Clippard? They have a valve for under $25-
http://www.clippard.com/store/byo_electronic/byo_mouse_valves.asp

There's tons of companies out there but you have to do a Google search and do some serious digging to get all the info/pricing.

[nidobrito]

Still a little expensive, what most impress-me is the fact of the inexistence of any solenoid valve tutorial on instructables...we have almost everything on here, eletromagnetic rifles, cookies, robots...but not valves...

If someone achive sucess in building a cheap and simple substitute to the solenois valves in this kind of project i hope that he posts the tutorial here...

=D

[Honus]

The only problem with making your own electronic valves is that they would probably cost more than the commercial ones! I've seen a three way aquarium valve operated by a servo but the problem is they can't hold high pressure- and it still cost nearly $15 to make.

[NightHawkInLight]

Very cool. This could allow for very quiet operation, especially if a lightweight liquid was used rather than gas.

[tilmen]

cool actuator for a robot

[maxxion]

Okay, I'm trying to make a "puppet" of sorts (Idea already start failing from here, BUT wait it gets worse). Its design has four legs, however Im having massive trouble trying to make it: Walk, keep balance, and turn. Someone suggest I use these, and I can potentially see how to walk and turn it......Maybe. The big problem is, controlling all four legs in sequence so it actually moves forward...and making it balanced so it doesnt fall over when it tries to move. Any ideas?

[maxxion]

Something I forgot to add.....Im trying to make it able to support me on top of it. Would possibly some sort of hydraulic system work better?

[Honus]

Boy I don't know. You would have to use a microcontroller to send signals to control the valves at just the right time and then have an accelerometer/gyro IMU to try and stabilize it. I don't know of anyone that's ever built anything like that before. The closest thing are I've seen are some of the systems that Festo builds.

[Rasna2011]

how exactly the air releases from the air muscle?Please answer me soon .i need this for my project............

[Honus]

Air is released when you open the air valve from your air source. Both two way and three way air valves allow you to vent the air. If you have any other questions just let me know!

[Rasna2011]

sir we have the three way air valve but that is of ''T'' shape where the air is entering through the single way and bifurcating to the both silicon tubes.after entering the air the silicon tube will inflate.Then how we will able to release the air through the valves?

[Honus]

Which valve are you using? Can you post a link to it?

[carlo.rousseeuw]

Goodday,

I've built de muscle, but if i put pressure on unloaded muscle, it does not contract alot at 30psi. Instead of other eamples where you say 60psi is allready enough to get the maximum displacement.

There is air flow, although i think not enough pressure. Or the tube is to strong ?
It is a tube of 2mm wall thickness, in stead of your 1/16 inch or 1,5mm.

I'm asking cuz i took a scare when the previous air muscle (without sleave) bulged out the end of the muscle untill it exploded there. And the muscle did not blow up homogenously.
Any thoughts ?

[Honus]

It sounds like you're using the wrong type of tubing for the bladder- what type is it?

[carlo.rousseeuw]

i'm sorry for my usage of the metric system:
All tubes are made of sillicone tubing and i've got 3 sizes:
8mm ID 12mm OD
10mm ID 14mm OD
6mm ID 10mm OD
(every wall is thus about 2mm thick)

IIf I may ask, about what maximum pressure have you put on the muscles ?
My muscle is about 30cm long made with the 8x12mm for the moment.

I don't have a weight on the muscle, so maybe that's the problem I't doesn't contract that much ( as you stated in your instructable)
thanks

[Honus]

The maximum pressure I've used is 60psi. The muscle really needs to be under tension in order for it to work properly so try using a weight or attach a strong spring to one end of the muscle.

[techno guy]

Where can I get some braided nylon mesh? Is there a store that I can buy this at? Are you sure that I cant buy it at amazon?

[Honus]

Have you done a search recently on Amazon or Google for the small mesh? I purchased the small braided mesh from a local small electronics surplus shop but Amazon does stock the 1/2" mesh.

[RoughRat]

The 1980's TV series Spitting Image in the UK used this for matching human movements in some of their puppets. They used sections of fire hose and a seriously high psi, if I remember right around 400!
They used it for natural rotational movements by coiling it around the section they wished to rotate after attaching one end to it and the other to a fixed point on the structure of the puppet.
They told me at the time they had a few nasty accidents developing this, mainly getting whipped or hit by high pressure hoses.
They also said that hydraulic systems were "a pain in the a**! " But they could be wrong....
Thank you all for such wonderful info :)

[Honus]

That's pretty interesting- I hadn't thought about coiling around to get a rotational movement. 400 psi would require some serious safety measures! Hydraulic systems are a PITA but for controlling movements in large heavy mechanics it's the way to go.

[W trouble]

how much do they contract?

[Honus]

They can contract up to 40% of their length.

[W trouble]

say i can figure out how to hook up a bunch of muscles to a co2 paintball tank, and put the tank on my back or something, is there any way so that i can bend my arm and it "amplifys" my motion so i can pick up heavy things, like iron man?

[Honus]

You would have to use something like a bend sensor or a potentiometer at each joint to measure the bend or rotation. This would then send a signal to a microcontroller that would control a solenoid valve to regulate the airflow into the muscle. The problem with this is that it doesn't know the difference between you just bending your arm and you exerting a muscle force. What you really need is a myoelectric sensor to be able to read the muscle contraction.

[W trouble]

Thank you.
I am just a kid so i dont think i can get my hands on those things...yet.

[W trouble]

it sounds like you are building an IRON MAN, you have posted instructables on animatronics, pneumatic muscle, arc reacter,

[Honus]

Nope- but I am helping out some friends with their Iron Man costumes!

[boomer6966]

My first thought... finally a way to make powered armor for military purposes. As in 'Starship Troopers' by Heinlein (the book NOT the POS movie).
My second thought is what would happen if this was switched to hydraulic versus pneumatic?
Thoughts anyone?

[drac03710]

How about Pneudraulics? I know our aircraft struts work that way...

[mikeasaurus]

pneumatic vs hydraulic, depends on the application.

Both have their benefits: pneumatic is light, compressible and may be cheaper to manufacture, hydraulic offers power, silence, and wider operating parameters.
In a 'powered' suit, I think pneumatic might be a better option due to cost and weight.

The book was more involved, but the movie was a smart adaptation I thought. The movie was definitely better after reading the book though.

[bowmaster]

For a suit I would use a combo of hydraulic a pneumatic. Hydraulic for large, high power movements (think arms and legs) and pneumatic for smaller, lower power movements (think fingers).

[TMC]

Hydraulic would prob be best for both. While fingers don’t require much strength they would need the precise controllability of a hydraulic actuator. Air is compressible so it would be difficult to control how much the 'muscle' contracts.

[rabid_engineer]

Yes and no... Hydraulics would provide precise positioning, yes... but hydraulics are also an order of magnitude more complicated to maintain than pneumatics. There are advantages and disadvantages to all types of actuators, I think, and to build a power suit, many different techniques should be used, to get a result that is greater than just the sum of its parts.

[Unsafe At Any Speed]

Great instructable, I can see some cool Animatronics projects in this! Would the outer covering on some Double Braided or Diamond Braided nylon rope for this? Just remove the core material from it and you would have sleeving material that I think would be a little stronger and less abrasive for the tubing than the electrical sleeving. -Just a thought.

[Honus]

I say give it a shot and see how it works- I really can't see any reason why it wouldn't work.

[Ghunter10]

I might of missed it earlier but did you mention the overall price of the material?

[Honus]

I don't believe I gave a total cost. I obtained most all my materials from a local hardware store and the braided sleeve from an electronics surplus shop. The muscles are very cheap to make- probably less than $10 each.

[DehLeprechaun]

can one use steam to do it or would that damage it?

[Honus]

Steam to do what?

[DehLeprechaun]

to contract the muscle just wandering if it might warp or damage the muscle in any way

[vignesh1230]

Is it possible to make a large muscle with longer tubing like the small one? I cant make barbed ends.

[Honus]

Yep!

[R3mus]

You didnt include how you're letting the air back out of your system. Are you using a three way solenoid? How do you have it hooked up? Ive got a two-way solenoid that Im using, and I just now realized that I forgot to configure it to let air back OUT. So it'll inflate till it pops lol. I think I need a second solenoid to allow a deflate, but I wanted to get an idea of how you did it.

[Honus]

I'm just using a manual valve that bleeds the air.

[R3mus]

Oh, so no automated inflation then? I guess Im taking it a couple levels higher than you. Ive got a microcontroller, and I just bought a pressure transducer to automate the inflation/deflation of it.

[Honus]

Nope- strictly manual!

[Doc Holliday]

A User Group/Blog is really needed for this.

There are simply too many applications to mention (and pursue) here.

This gets my vote for  a "best instructable" 2010.

[nabilm]

Here is a very serious and scary application of this (shadowrobot.com).

I would love to see more applications of this and also if there are  other alternatives to emulate the human muscles.

[Honus]

I've seen that before- it's pretty amazing stuff.

[nabilm]

Check a video of the hand in action using the air muscles :-)
http://www.youtube.com/watch?v=jMHvziAikok&feature=related

[jacksteal4]

as i'm sure a lot of people have already said... That would be an amazing prosthetic! you could have a little air tank in an arm and i don't really know how you would control it but it would be sooo coool!

[snobound2]

Just discovered this post today.  All I can say is WOW!
This has so much potential.
As for braided mesh, how about the braided copper wire shielding on some coaxial cable.  The copper mesh can be soldered to a fastener at each end to make attachment easy. Granted it is not very big around but several smaller muscles in tandem can exert a lot of power.  Also, how about liquid rather than air.  Liquid does not compress and you may end up with a stronger, more responsive muscle.  A mechanically driven syringe would work as a source of pressure.

[Honus]

Thanks- those are some really interesting ideas! Of course liquids weigh more than air but it's a neat idea worth experimenting with.

[quellek2]

 This reminds me soooooo much of the muscles on the robots in the movie iRobot

[TitanTechRobotics]

That is because the muscles on the robots, were this kind of muscle.  Cool how they made it a little more realistic.

[Ghunter10]

This is great, i will definetly use these

[Ghunter10]

how could you make it stronger, by size? or could you keep the same size just stronger more stretchable material?

[Honus]

By size- that's more important than the ability of the material to stretch.

[Salsa766]

 is that the leatherman juice s2?

[Honus]

Yep!

[I_am_Canadian]

I was hoping this instructable was going to be on those things you put on your arms and inflate to make it look like you have huge muscles.

Ah well. This is very cool as well :-)

[dutchypoodle]

HA, yes-- I had similar thoughts when I clicked the link. I was almost dissapointed, but as it turns out the actual article has more practical applications.
Flex-eriffic, Honus.

[TitanTechRobotics]

Where did you get your nylon tubing from, was it amazon, or was it an electronics store, because I want to build one of these, but the electronics stores that i order from don't have the nylon sleeving.  If you did order it from a electronic store, which one is it.  I looked around at some, but couldn't find any reputable, and digikey only had very long lengths.  Also I looked at some speed shop websites, because the sleeving is used to protect tubing from heat, but there was no diameter selection.  Thanks in advance.

[Honus]

I bought it from J.B. Saunders- http://www.jbsaundersco.com/

They're a local electronics surplus supplier that I use.

[OverSaltedFry]

Very cool stuff, its amazing just how strong these air muscles can be.

The braided nylon sleeve reminds me of thoes chinese finger trap things where you put a finger in each end and cant get them out.

[Arbitror]

Is the air muscle originally your idea? Because it is probably the most inventive thing that I have seen on Instructables! This is one step closer to a perfect android!

[Honus]

Oh no, it's been around for quite some time. Not that many people seem to know about it though.

[Arbitror]

It's a brilliant idea, though. Try putting two together like a human arm, with one contracted while the other is extended. See how much that could lift!

[frankendaddy]

Festo, Inc. makes one that they use in industrial automation. I think that the first one of these was called a McKibbian Artificial Muscle.

[Honus]

From the intro- Air muscles (also known as a McKibben artificial muscle or braided pneumatic actuators) were originally developed by J.L. McKibben in the 1950's as an orthotic appliance for polio patients.

[Foaly7]

Sweet. I'll try that with my RoboSuit that I am planning.

[xproplayer]

*insert evil laugh here*

[Foaly7]

Actually, I don't really think I will even build such a suit, because I totally forgot about that old project until you replied to my comment. :-P

[xproplayer]

oh i get it cover your tracks

woops sry for the spoiler

[Foaly7]

No, seriously. I'm focusing on stuff other than robotics at the moment.

[xproplayer]

Suuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuure

[Foaly7]

Seriously, man.

[xproplayer]

lol fine it was a good joke tho

[INSTRUCTUBAL]

 hes working on extracting the human brain to put in the cyborg.
*insert evil laugh here*

[Foaly7]

DRAT!!! FOILED AGAIN!!! Who are you? Where are you? Who do you work for? What are you? How did you find my secret laboratory? Forget it!! Jimmi, we've been compromised! Abort! Abort! Get ready to R--U--N--N--O--F--T!!!!!!!! D***, we're in a tight spot.

[xproplayer]

Secret Ur moms bed International fool all evil plots (ifaep) Human It was obvious it was a big sign that says "mysteriousdragons lair!" dam str8

[Foaly7]

Wait, that's the decoy lair... I thought you were in my dog's bed. How did you find the other lair? It has flashing lights around its sign.

[INSTRUCTUBAL]

I killed Jimmi.

[Foaly7]

NO!!!!!!!!! Not Jimmi! He was just a Lad!!!!! This is personal, now. Ur goin down, INSTRUCTABAL!!!!!!!!!!!!!! :)

[bowmaster]

Don't worry!! I've sent a squad of Lady Gaga's ninjas to save you!!

[Foaly7]

Oh my god!!!! Ninjas working for a man-lady!!!!!!

[bowmaster]

Oh, called them back because of that comment. You're on your own now. Prepare to die.

[jtpoutdoor]

Very cool. For materials- try dairy farm suppliers, lots of rubber (and silicone) hoses used in the industry- but in heavier sizes- 1/2, 3/4 inch. For outer braided sleaving would the sheath of a kernmantle rope do? It would be nylon so might have too much stretch in it? They are reasonably easy to remove from a rope and the rope comes in various sizes.

[Honus]

I don't know about that for sheathing- I guess you would just have to try it and see how it works.

[frankendaddy]

you can get metal braided tube at electrical supply stores (Kirby-Risk or Kaman Industrial Technologies)

[nidobrito]

how i fix air leaks in the muscle? my muscle is not full contracting...if i put a more large(in diameter) internal latex tube, will fix this problem? TNKS

[Honus]

If it's leaking through the ends then you don't have a good seal and need to clamp the bladder tighter. The muscle will only contract a portion of it's length. The total contraction depends on the type of tubing you use for the bladder, air pressure and the fit between the mesh and the bladder. A larger bladder may help- you're just going to have to experiment.

[nidobrito]

hohoho tanks

I will try a larger bladder because i build they to full contract and put a large pressure on the but they don't full contract...(low weigh loaded)

ah, i wrote wrong... not air leaks but air gaps between the mesh and bladder when the muscle is contracted..if you know how to solve plz tell me

ah have you plans to a homemade solenoid valve? because they are very expensive....and i need some of these..... if you have plans plz send-me tanks

[Honus]

It sounds like you need a mesh that fits tighter around the bladder. Unfortunately I don't have any designs for a homemade solenoid valve.

[nidobrito]

oh OK I will try with a more larger bladder because I'm using the smallest mesh that i found...tanks

[Deus Tempestas]

I had a dead power supply from a computer, the main mass of wires had a braided nylon mesh tube around them. 0$

[jnordstrom]

What is the best way to accurately control a set of opposing mussels, example human leg, I have been researching 2/3 way solenoids and IO controllers connected to a PC. Should I use two 2-way solenoids per mussel, one to let air in and the other to let air out, 3 way solenoids let all of the air out, I assume one would want to let only some of the air out for precise control. Also how do I partially inflate/deflate the mussel, using timing? E.g. open the solenoids for 0.10 seconds, 0.20 seconds, I assume an electronic PSI controller e.g. fill the mussel with 20 PSI, now 25 PSI etc would be better, does such a thing exist?

[toohuman]

The problem with this muscle actuator type is that it's impossible to develop control systems anywhere near as good as a the dozens of force pairs and thousands of recruitment patterns that a human extremity contains. Add that to the fact that the actuator isn't self contained and you've got a fun toy with no real chance of being an effective actuator for prosthetics.

[jnordstrom]

I am working on building a full size humanoid with similar but simplified human mussel movement and simplified (more traditional robot) joints. The PSI of both the input and the output must be controllable, controlling how fast the mussel will contract and release. The solenoids seam to only support fill or vent (I don’t understand the hold part of a solenoid, I only see fill and vent?), I could use short burst at 60PSI but that creates unnatural jerky movements. I guess what I need is a digitally adjustable regulator? I think that would solve the issue. So for slow movements I would say fill at 20PSI until you reach 20PSI. For fast movements I would say fill at 60PSI until you reach 60PSI. I hope I am using the right terminology I’m assuming flow rate and PSI are synonymous. These could also be combined, when moving a leg or arm, move quickly until near the destination then move slowly. Or fast, medium to slow. There must be products like this with all of the industrial uses of air. Thoughts?

I found a pressure sensor but it does not support 60PSI and does not do totally what I wanted.

http://www.trossenrobotics.com/store/p/3226-Pressure-Sensor.aspx

For the controller I plan on using several InterfaceKit 0/16/16 from Trossen Robotics connected to an AMD quad core with 8GB RAM. I plan on writing the controller code in Java using the drools rule engine.

http://www.trossenrobotics.com/store/p/3201-InterfaceKit-0-16-16.aspx

[Honus]

You might check out Festo's website: http://www.festo.com

They have all kinds of valves and controllers and they built a really incredible pneumatic arm.

[jnordstrom]

Great site I'm digging through the product catalog, and thanks for the previous links, very informative. I did find one item that may offer the precise control I was looking for http://www.controlair.com/transducers/900trans.html

[Honus]

You would probably have to use 3 way solenoid valves and connect them to a microcontroller with a pressure sensor installed at the end of the air muscle. The pressure sensor would tell the microcontroller when a desired pressure is reached and then the microcontroller would tell the valve to either fill, hold or vent. I'd imagine you would need to interface the microcontroller with a computer to be able to make it all work together. A lot of large movie animatronics are controlled this way using hydraulics with the computer telling the controller which valves to open and when. I have yet to do anything like this but you could probably do it using MAX/MSP or Processing and using an Arduino or MAKE controller.

http://www.cycling74.com/products/maxoverview
http://processing.org/
http://www.arduino.cc
http://www.makingthings.com

[jnordstrom]

I like the aluminum rod as it looks like it would provide a proper seal and be strong, the piece is no longer available on Amazon can you recommend another provider?

[Honus]

There are lots of online metals suppliers- try here:
http://www.onlinemetals.com/merchant.cfm?id=195&step=2&top_cat=60

[Helio]

It turns out McMaster Carr doesn't ship to Canada unfortunatly. Does anyone know where I might be able to get latex tubing with 3/4" OD in Canada? Any help would be really appreciated! Great instructable btw, very very well done and informative! Also for anyone interested I found that a moderate substitute for latex tubing is a bicycle innertube.

[Arbitror]

Rona.

[Capt. Fat]

Great instructable! Espically for people who like to use less effort to lifft things. Any way you could make it with simpeler household materiels?

[Honus]

Thanks! They're pretty simple to make- the mesh is a key ingredient so I don't really know what else you could use.

[longineus]

Great Instructable! What is the OD\ID relation between the mesh an the rubber tubing?The mesh must have a larger diameter than the tubing OD or it can be a snug fit?

[Honus]

Thanks! The mesh must be a larger diameter than the tubing but it can be a snug fit.

[DELETED_Robert L]

(removed by author or community request)

[Honus]

An electronic switch (like a transistor) could be used to turn a solenoid valve on to inflate the air muscle.

[DELETED_Robert L]

(removed by author or community request)

[Honus]

There are companies that sell little solenoid valves. They work just like a sprinkler valve- when you apply voltage to the valve, the valve opens and lets the air flow.
Have a look here:
http://www.vexrobotics.com/vex-robotics-pneumatic-parts.shtml#vex-pneumatics-kit-1a

[egriff]

Now what I have a problem with is how can I get one muscle to expand and another to contract at the same time. A switch to turn one solenoid valve on and the other off is easy, but how do I get the air out of the contracted muscle?

[Honus]

A solenoid three way valve works by first filling the bladder, holding the air pressure in the bladder and then venting the bladder to atmosphere deflate it- when the valve is opened it will automatically deflate the contracted muscle.

[egriff]

now that I've been doing some searching, do you know a source of low cost 3 ways? About the cheapest I've found is about $70.

[Honus]

Here you go: http://www.imagesco.com/catalog/airmuscle/AirMuscle.html

Just scroll down- the one you want is the AV5-01 and it sells for $35.

[egriff]

I've noticed that most of the silicone tubing at mcmaster has a max psi of 30, should this concern me?

[Honus]

That will ultimately limit the load capacity of your air muscle. It just depends on what you need. For a small muscle it should work just fine as long as you watch your air pressure. For a larger muscle you would be better off using latex tubing or silicone tubing with a higher rating.

[egriff]

thanks, I'm going to use the other air muscle guy's idea and have the contracted muscle bleed into the extended muscle. I can't wait for the holidays to be over so I can focus on this project.

[egriff]

ahhhhh, thank you.

[DELETED_Robert L]

(removed by author or community request)

[Honus]

You're welcome! If you have any more questions just let me know.

[egriff]

http://www.youtube.com/watch?v=sJ4J69EEpu4

I saw this and nearly fell out of my chair... freakin' insane.

[Honus]

It's pretty amazing what $75 million in DARPA funding will do. The biggest problem is powering it- I don't think anyone has yet won the X Prize challenge for a suitable power source.

[egriff]

arc reactor of course.

[Honus]

Well the arc reactor looks to be based on a Tokamak so maybe someday........

[l96470fps]

great job !! but will inner tube work??

[Honus]

If it's a latex inner tube it might. I don't know about a butyl rubber inner tube- give it a shot and see what happens.:)

[Helio]

Does anybody have any idea of where to find latex tubing that is 3/4", 1 1/4", and 1 3/4 in diameter? I'm having a hard time finding anything that big.

[kelseymh]

McMaster-Carr Industrial Supply has latex tubing up to 1-1/2" OD. They also have soft (60A durometer) buna-N tubing up to 2" OD.

[budsiskos]

im having trouble finding the nylon mesh sleeve. what store did you buy it at? are there any possible substitutes?

[Honus]

I bought it at a local electronics surplus store but it has also been sold on Amazon (there's a link in step 1.)

[botmaster 10]

No! Mc master.com Search for nylon sleeve

[bombmaker2]

is 3/8" the id or od

[Honus]

It's 3/8" OD. If you have any other questions just let me know.

[Vindoch]

even if the muscle's material however perfect for the job, isn't its still depends on the compressor's power(compressor/air pressurer name it)? sorry if misunderstand

[Honus]

Beyond a certain pressure, having a larger compressor won't make for a stronger muscle. A more powerful compressor might be able to inflate the muscle faster, but it wouldn't increase the muscle's load capacity. If a muscle fully contracts at 60psi then having a larger air source won't make it any stronger. To demonstrate this, inflate one muscle with a bicycle pump and another muscle with a compressor. They'll both do the job but one will just be much slower than the other.

[mkamchin]

What could you use an air muscle for?

[Honus]

From step 4: "Several applications of air muscles include robotics (especially biorobotics), animatronics, orthotics/rehabilitation and prosthetics." Basically they can be used in applications use pneumatics, hydraulics or gear drives to create motion.

[thinkahead]

...wonder if a version made from PVC might be better for some applications...?

[budsiskos]

but wouldn't that just be a pneumatic actuator?

[incorrigible packrat]

Neat. Now I have something to do with the silicone tubing I get out of defunct drip coffee makers... A while ago, I saw a show on TV, where researchers were working on prosthetic limbs powered by steam. The steam was produced by catalytic breakdown of hydrogen peroxide. I think the actuators were air muscles. (I didn't pay particular attention to the actuators, too captivated by the steam thing.)

[SWV1787]

I suppose if you were to try to make a simulated human arm you would need to find a way to maintain high enough pressure and then re rout the air from one set of "Air Muscles" to the next to create flexsion and extension. I think this is awesome but I would not want to be right next to it when the tubing wears out and snaps dropping whatever weight it was holding.

[jasonx]

cool now build one of these

[Honus]

I saw that on Festo's website- it would be very cool to build. I'm sure I could handle the mechanical end of building it.......interfacing it with a sim game- that 's another story!

[thecheatscalc]

Now that's an interesting idea... not too hard a concept really... the real question is how much air and pressure does it use? if it's not too much I could see this being a good asset... if not, well, it's still really cool! Oh, and you don't have any links to those "bend sensors" and the corresponding microchip, do you?

[Honus]

The amount of air they use is dependent on the muscle size- the small muscle has very little air consumption. Both the muscles I constructed were tested up to 60psi but air muscles in general rarely exceed 90psi and can operate as low as 20psi. Again, a lot of this depends on the particular muscle construction.

As for the bend sensors and microcontroller have a look here: http://www.instructables.com/id/EH2BKVEF1U9XT76/

I'm currently working on a three way servo operated air valve that will be simple to construct.

[TheMadScientist]

oh, my, god... now to get some medical grade surgeon's tubing and you're one step closer to a robotic humanoid

[Honus]

Take a look here: http://biorobots.cwru.edu/projects/c_mrobot/c_mrobot.htm
A two inch long cricket powered by air muscles with its own tiny on board air compressor!

[BlessedWrath]

Yes, that's where I'm going with this. A powerful battery, supplemented with solar cells, or other secondary power source, with the smallest effective air compressor (to lower weight), and movement activated control switches, attached to a lightweight metallic frame. Anyone want to run at 55 mph?

[bowmaster]

Hey you stole my idea!!! Great minds think alike I guess.

[Honus]

Have a look here:
http://www.umich.edu/news/index.html?Releases/2007/Feb07/exoskeleton-vids

And here:
http://www-personal.umich.edu/~ferrisdp/pneumatics.html

This is also pretty cool:
http://news.com.com/2300-11394_3-6120170-1.html

[Honus]

I've actaully seen something like that- sort of an exoskeleton. What would be an interesting experiment is to attach them to the crankarms of a bicycle- there would be a sensor pickup on the crankarm that would activate the muscle on the pedal upstroke. The muscle would be fully extended on the pedal downstroke- could be fun to try out! :P

[BlessedWrath]

Is it conceivable to link the control box to multiple switches, each designed to fit around a human body part, such as fingers? I envision a "glove" with mechanical devices in it that trigger the pumps on the corresponding muscles as the user moves the individual parts of his hand.

[TheMadScientist]

looking into this, I was thinking of emergency sensors for things such as saving peoples legs in a greater than average fall [a story or two off of a building] and stuff like that

[Honus]

Yep- I've previously made a glove that uses bend sensors (you could also use piezo/force sensors) that is connected to a microcontroller. The microcontroller would then tell electronic soleniod valves to work the individual muscles.

[BlessedWrath]

How strong can the muscles become? Is this technology capable of exerting enough force to equal human muscle? If so, how much greater/smaller would the size/strength ratio be by comparison?

[Honus]

Commercially available muscles that measure 30mm diameter x 290mm long (stretched) can pull 75kg.

[TheMadScientist]

well, that all depends on the strength of the material, and making sure that the inner membrane is completely non-permeable

[tanntraad]

I love it. Great work! I just published my instructable on simple animatronics and this is just the info I need for future projects!

[Honus]

Thanks! I saw your hand instructable and thought it was really creative, especially since I'm a big Halloween guy. :D If you need any help with your projects just let me know- I'm working on several animatronic projects right now.

[rickharris]

You might find these useful
shadow robot
how to make

[Honus]

Thanks! I'm familiar with Shadow- the work they've done is extremely impressive to say the least. Merlin Robotics is also doing some fantastic work.
http://www.merlinrobotics.co.uk

[rickharris]

or indeed this link to the soda bottle system TEP.org

[Patrick Pending]

Great work, it has everything a good instructable should have.

[rickharris]

provided you don't need a large pull you can use a normal balloon and braiding (generally available from electronic suppliers (rapidonline in the UK) The metal fitting is only there to give something for the hose clip to tighten onto so could be anything suitable with a hole in it - e.g. a bit of metal tube. Soda bottle with a modified cap to allow 2 tube to be attached and some plastic valves from your local home brew beer supplier will make a suitable pressure vessel that can be pressurized with a car foot pump.

[Honus]

I plan on using the soda bottle as an air tank for a future project with some small air muscles that will be controlled by a microcontroller. There are a ton of possibilities..... :)

[NikonDork]

By far the coolest instructable evar! Question though: I dont have access to a lathe. Is there any kind of fitting out there I could use to make the large muscles? Instead of having some custom machined?

[Honus]

Just scale up the small muscle that I made. Use a large brass or plastic hose barb for each end- you'd want one that has a barb to standard pipe thread connection so you can cap one end off and still get your small air inlet on the other end. Use the safety wire loops I described but make sure you use steel hose clamps to secure them. I might make a larger one using this method- I have a large anvil at work I want to lift! :D

[ARVash]

For large muscles just add a few of them, not sure if that's the response you were looking for, but it'd work :P.

[stevoIution]

Bringing pneumatic muscles to the masses. Nice work! +