Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: Ocelot on July 11, 2011, 08:33:48 AM
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Hey All,
I'm currently working on a pneumatic air muscle powered jumping robot and would like some help with picking the right solenoid valve.
The one I'm currently using is a Mead Isonic 3-way (normally closed) valve. http://mead-usa.com/products/detail.aspx?id=28 (http://mead-usa.com/products/detail.aspx?id=28)
Here are the specs...
Voltage: 5 VDC
Amps: 320 mA
Orifice Size: 0.9 mm
Flow: 0.02 Cv
Max Pressure: 120 PSI
Tubing: 5/32"
Dimension (in): 1-9/32 x 1-3/4 x 5/8
Weight: 1.5 oz
Response Time: 10 ms
I've been testing the solenoid valve by inflating an air muscle with a 10lbs load on it and I'm disappointed in the inflation rate/response of the muscle. I've tried increasing the pressure from 60psi to 80psi and that helped a little bit but I'm thinking I'll probably want to increase the inflation rate/response to generate a larger impulse for jumping.
So here's my question...
Should I get a solenoid valve with a larger flow rate or should this size suitable for my application?
If so, can anyone suggest a similar solenoid valve (5V, weight, dimensions) to use but with better performance (flow rate) properties?
Thanks for the help!
Brian
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Please forgive my interjection, I'm a total noob as far as robotics is concerned, but have been a mech eng for the past 25 odd years!
From the stats given for the valve in question, I would say that its the orifice size thats holding back the flow to the air to the muscle, not the response timing.
The other issue I can see is the muscle itself, if its like the other pneumatic muscles I've seen, then the initial flow and pressure feeding it will simply be wasted on inflating it, rather than actually moving it. Like an innertube in a tyre, it requires a certain volume of air before it meets the required resistance to actually build pressure.
I think that a small, rigid actuator may be the way to go, due to the fact of it not having to contain a specific volume of air, before it starts to move.
Given enough orifice diameter, and a suitable bore and stroke of cylinder, and as little resistance to airflow as possible, even relatively low pressures should result in a fast, powerfull movement of the actuator.
Hope this helps, or at least gives food for thought!
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Please forgive my interjection, I'm a total noob as far as robotics is concerned, but have been a mech eng for the past 25 odd years!
From the stats given for the valve in question, I would say that its the orifice size thats holding back the flow to the air to the muscle, not the response timing.
The other issue I can see is the muscle itself, if its like the other pneumatic muscles I've seen, then the initial flow and pressure feeding it will simply be wasted on inflating it, rather than actually moving it. Like an innertube in a tyre, it requires a certain volume of air before it meets the required resistance to actually build pressure.
I think that a small, rigid actuator may be the way to go, due to the fact of it not having to contain a specific volume of air, before it starts to move.
Given enough orifice diameter, and a suitable bore and stroke of cylinder, and as little resistance to airflow as possible, even relatively low pressures should result in a fast, powerfull movement of the actuator.
Hope this helps, or at least gives food for thought!
Thanks for the quick reply!
Isn't the flow rate of the solenoid valve is determined by the orifice?... I was basically asking the same thing but in a round about way (eg do i need a solenoid valve with a larger diameter to increase the flowrate?). Mead does have one larger orifice size but the max pressure for the valve drops to 30psi which is way too low for my application.
Solenoid valves aren't my realm of expertise so I wanted to see if a more experience person can take a look at those specs and say "Hm yeah that orifice looks kinda small you'll want to get one in XX size. This valve might work better...".
I'm going with the air muscles instead of a rigid actuator because of its superior power/weight ratio. I wish I could track down the specs of the components used for this jumping robot. Its pretty close to what I'm going for.
Mowgli: A Bipedal Jumping Robot (http://www.youtube.com/watch?v=cs70YDdppjk#)
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http://www.alphacontrols.co.uk/pdfs/alpha/solenoid%20valves/ACLSM31%20&%2041.pdf (http://www.alphacontrols.co.uk/pdfs/alpha/solenoid%20valves/ACLSM31%20&%2041.pdf)
...any of the smaller valves on this page suitable??
They have larger orifices, and higher flowrates, however they dont seem to operate at 5v, and not sure of the overall weights, as they're not listed.
nb: they are available with 6v solenoids!
edit: what size is the inlet orifice on the muscle?? Would it allow for using 2x of the solenoids you have, in parallel, doubling the flowrate and orifice size??
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http://www.alphacontrols.co.uk/pdfs/alpha/solenoid%20valves/ACLSM31%20&%2041.pdf (http://www.alphacontrols.co.uk/pdfs/alpha/solenoid%20valves/ACLSM31%20&%2041.pdf)
...any of the smaller valves on this page suitable??
They have larger orifices, and higher flowrates, however they dont seem to operate at 5v, and not sure of the overall weights, as they're not listed.
nb: they are available with 6v solenoids!
edit: what size is the inlet orifice on the muscle?? Would it allow for using 2x of the solenoids you have, in parallel, doubling the flowrate and orifice size??
Hmm those are 2-way valves. I'm looking for 3-way valves normally closed so I only need one valve instead of two (for 2-way valves you need one for intake control and one for exhaust control; for 3 way valves you just need one.. intake when energized, exhaust when de-energized). I'm basically trying to fill the air muscle up as fast as possible then venting it when it reaches the threshold pressure.
There is no orifice on the muscle. It's just tubing straight from the solenoid valve to a push-to-connect fitting on a barb. I believe the ID of the barb is 5/16in.
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http://www.solenoidvalvesuk.com/catalogue/filecatalog/H%202010.pdf (http://www.solenoidvalvesuk.com/catalogue/filecatalog/H%202010.pdf)
Ok, 3 way, range of orifice sizes, still rated to reasonably good pressure even at 2mm+ orifice diameter, and nowhere near as heavy as brass/ alloy valve bodies.
...any of these take your fancy?
...or just use 2x of the ones you have in parallel?!
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http://www.solenoidvalvesuk.com/catalogue/filecatalog/H%202010.pdf (http://www.solenoidvalvesuk.com/catalogue/filecatalog/H%202010.pdf)
Ok, 3 way, range of orifice sizes, still rated to reasonably good pressure even at 2mm+ orifice diameter, and nowhere near as heavy as brass/ alloy valve bodies.
...any of these take your fancy?
...or just use 2x of the ones you have in parallel?!
Ohhhh I finally see what you mean by doubling the valves in parallel. That's brilliant. I think I'll give that option a whirl.
Thanks for the awesome advice!