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Join Date: May 2011
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Digital Resonant Pneumatic Multi Valve

08/29/2020 2:54 PM

I'm not sure if such a thing exists, but I just thought of it and want to know if it would work and what industrial legos are needed to test it.

The problem: Due to back problems I wanted an air mattress with fine control of pressure in specific parts that varies by program through the night. I found a 40 chamber mattress that would take 40 1/4"ID plastic airlines. I did not want to also have to wire up 40 solenoid valves, or 40 air pumps along with the 40 pressure sensors.

The potential solution: Use 1 air pump, 1 digital control proportional flow control solenoid valve, and 40 N/C reed spring valves.

I'm not sure of the terminology so help my Google fu by correcting me.

Instead of operating the solenoid valve at a constant frequency and varying duty cycle, it would have a fixed 50% duty cycle (hopefully sine like flow variations), and vary the frequency over the widest reliable range. Probably a needle valve attached to a speaker voice coil is closer to what I need. Is there an industry term for that?

What I called 40 N/C reed spring valves aren't really reed valves because I think they all need identical cv and port geometry, like the valves on a flute. But the arms holding the 'caps' closed are leaf springs, each a different length, thus a different resonant frequency. Or maybe I'm wrong about that and they need to be regular reed valves to operate properly with lower frequency reeds flowing more volume. In which case... I don't really know. Not my field. Maybe we need a 2nd solenoid for dynamic per frequency pressure control.

Principle of operation: Based on the programmed pressure map and feedback from mems pressure sensors, the solenoid operates at the resonant frequency of a specific reed valve connected to a chamber that needs to increase pressure. Being resonant, it flows more than all the others leaving less manifold pressure to push open the other valves. The digital controller sweeps through the frequencies of any valve connected to a chamber that is low. If a chamber is over pressured and needs to be reduced, its frequency is applied, but at a lower duty cycle. That should produce a lower manifold pressure than the chamber, but still operate the reed valve at low amplitude.

This isn't positive valve control, its dynamic. There will be leakage. Harmonics will open unintended valves, solenoid nonlinearities will produce aberant frequency content. Hopefully the electronic control loop is fast enough to compensate at the cost of longer than optimal pump run time per correction. The lowest frequency valve will probably need a static dump pressure regulator set to the lowest anticipated pressure.

Other applications: off road vehicle suspension, Stewart platform (simulator motion platform), single human transport off camber suspension(Segway, wheelchair, trike). Keep a wheelchair seat level while going crosswise down a hill.

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#1

Re: Digital resonant pneumatic multi valve

08/29/2020 4:38 PM
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#2
In reply to #1

Re: Digital resonant pneumatic multi valve

08/29/2020 5:14 PM

And now for something really expensive...

..."The Freedom Bed™ is a unique, computer-controlled, therapy system that manually or automatically turns the bed-user to different stable sleeping positions without the aid of caregivers or institutional staff.

The bed closely mimics the body's natural nocturnal motion by mechanically repositioning it in order to re-establish blood flow to compressed tissue and thus prevent the formation of life-threatening bedsores and other complications of immobility. The motion is timed (rather than random) when under computer control and the rate is adjustable to permit the accommodation of a wide variety of sleeping patterns. "...

https://inclusivetechnologies.org/products/freedom-bed

I have found that doing deep knee bends every day keeps my back from aching....

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#4
In reply to #2

Re: Digital resonant pneumatic multi valve

08/29/2020 11:18 PM

That's pretty cool. My mother-in-law could use something like that.

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#3

Re: Digital resonant pneumatic multi valve

08/29/2020 8:52 PM

Are you going to get any sleep with the noise from these resonant valves?

Here is something along the same lines that you are proposing.

https://core.ac.uk/download/pdf/12543994.pdf

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#5

Re: Digital resonant pneumatic multi valve

08/30/2020 5:29 AM

You are looking for a new technology to solve your problem. Why not use an updated old technology? Attach a rotary plate valve with one input and forty outputs to a stepper motor controlled by a programmer. Add a non-return valve after the pump and a solenoid exhaust valve with flow restriction on a Tee between the pump and the plate valve to release air when you want to reduce pressure in any of the chambers. Place a single pressure sensor between the pump and the plate valve.

Step 1 The plate valve connects the pump, exhaust and sensor to the last chamber you adjusted.

Goto Step 2 To make a new adjustment, change pressure in the current chamber if required.

Goto Step 3 Run the stepper to select a new chamber. The sensor now reads pressure in the newly selected chamber.

Goto Step 4 Increase or reduce pressure as required.

Loop to step 1

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#9
In reply to #5

Re: Digital resonant pneumatic multi valve

08/31/2020 1:08 PM

I think this will be very slow to react. You could speed it up by having multiple motor devices and valves.

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#10
In reply to #5

Re: Digital resonant pneumatic multi valve

08/31/2020 1:43 PM

Yes! This is the most practical. I hadn't heard of a rotary plate valve but that is exactly what I need and you saved me a bunch on pressure sensors.

About 2 minutes after clicking send I realized I had almost described a pipe organ, so it would be intolerably loud.

Thank you all for so many excellent answers. I think I learned something from each one.

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#6

Re: Digital Resonant Pneumatic Multi Valve

08/31/2020 9:29 AM

Several different types basically all the same....~$2500- $2800 all in....

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#7
In reply to #6

Re: Digital Resonant Pneumatic Multi Valve

08/31/2020 11:10 AM

This table is pretty cool, you just need somebody working the controls....

$5400-$8700....

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#12
In reply to #6

Re: Digital Resonant Pneumatic Multi Valve

09/07/2020 9:08 AM

My chiropractor put me in a programmable massage chair,and when he left the room,I started fiddling with the controls,not knowing what I was doing.

To my surprise,this chair could imitate everything from a gentle boat ride to a bucking rodeo-killer-bull.It was bucking so hard I could not reach the controls to turn it off,and I was strapped in for the duration.Fortunately,it had a timer to turn it off after a couple of minutes.When the doctor came in,I looked like a cat that had been in a laundromat dryer,hair sticking straight up like a dandelion,eyes as big as golf balls,with tiny black dots in the center.

He grinned knowingly,and said"You made some adjustments I see."

However,it was not all bad..My back pain disappeared the next day.

Next time I have that back pain,I'm just going to ride a bull in the rodeo..only lasts 8 seconds,max,not 3 minutes.

Heck,I might even win.

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#13
In reply to #12

Re: Digital Resonant Pneumatic Multi Valve

09/07/2020 10:33 AM

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#8

Re: Digital Resonant Pneumatic Multi Valve

08/31/2020 12:50 PM

What you are describing sounds a lot like a servo pneumatic valve. The valve rapidly shifts between pressure and exhaust in response to some signal to maintain pressure or position. Valve type, Reed spring, poppet, spool, doesn't matter there will still be one valve and one sensor per chamber to have dynamic adjustments. If you separate the pressure and exhaust signals you can hold pressure for a while without opening the valve.

When they first came out we called them Buzz valves, one of the first ones was literally called "Buzzmatic" because of the noise it made. It sounded like a very large hornet. That might make it hard to sleep.

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#11
In reply to #8

Re: Digital Resonant Pneumatic Multi Valve

08/31/2020 2:07 PM
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