Controlling A Hydraulic Solenoid valve With PWM

   / Controlling A Hydraulic Solenoid valve With PWM #21  

oldnslo

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They may be trying to keep the valve partially open with PWM but not sure how well that works. The big unknown is the valve response time or ability to change to change directions. Does it take 20, 50, 80 milliseconds etc. to respond. Quicker response provided better control.

I believe Spectra physics was just pulsing relays but not 100 percent certain of that. These were also 40 GPM valves not 10 GPM valves.
 
   / Controlling A Hydraulic Solenoid valve With PWM #23  

orangetree

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The rates at which PWM can operate are meaningless to the operation of a solenoid valve, and oil flow, in my opinion. I could be wrong, but it seems like the so common trick of bamboozling people with terminology that seems to make sense but is really not applicable. Kind of like saying your computer utilizes "turbo" technology. What the F#%% does that mean?
Turbo comes from the old days when plenty of software (especially games, but also office sw) was coded with certain expectations of the processor's specific clock rate.

The "turbo" button just made the cpu run at its actual full speed, which "non turbo" essentially a compatibility mode. or, surprisingy, what i just wrote but opposite: "turbo" indicated slower clock speeds. You'll have to ask a marketing person how this makes sense :)

Today, "turbo" features are about heat. a modern cpu has FAR more functionality than could be run at once/continuously and stay inside the thermal envelope (both cooler capacity, and temp gradient inside the chip package itself). most functions are not working at the same time. similarly, higher clock rates go faster (duh) but also consume more power == produce more heat. turbo mode inside a cpu today plays with these pararmeters (esp clock speed) to make the most of the perf options available.

Tl;dr - definitely marketing speak, but the underlying functionality IS doing something helpful for the user.

Similarly, PWM _is_ how the underlying solenoids are controlled. But there is a fair amount of software/firmware on top dictating exactly how and when (reading feedback, etc), and some analog filtering below to customize the transfer function between digital input (pwm) and analog output (spool movememt).

[Edit for completeness - this can be done entirely with analog electronics; at one point in time it was done this way. However, with modern / cheap microcontrollers and sensors, given a certain (engineering +test + hardware) number of dollars, digital controls are typically the stronger choice]
 
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   / Controlling A Hydraulic Solenoid valve With PWM #24  

orangetree

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They may be trying to keep the valve partially open with PWM but not sure how well that works. The big unknown is the valve response time or ability to change to change directions. Does it take 20, 50, 80 milliseconds etc. to respond. Quicker response provided better control.
That is 100% correct.

The input is digitial (pulses; anywhere from 100's to megahertz depending on app/industry - idk what hydraulic proportional valves use, kHz would be common in general)

The output is a "transfer function" (systems speak)**, which quantifies how a particular input will translate in delay/amplitude/velocity/etc in the output.

There is a lot of characterization of the particular system that went into engineering the valve you buy. IE "tuning" to correctly handle exactly the parameters you mention, and more.

**these fluid problems are probably not exactly linear in many aspects. actual fluids engineer might be doing something mkre complex t.b.c.; transfer function requires system is "LTI"... that said an approach like this would probably have some success (?). Fwiw, this is highly similar to desiging an audio filter. same concepts and applications.
 
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   / Controlling A Hydraulic Solenoid valve With PWM #25  

orangetree

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Here's an analogy that is surprisingly accurate.

Stand at a teatherball pole, hit the ball repeatedly, trying to keep it, smoothly, at a specific height/distance from pole (straight out, not in a circle)

Small, well timed taps of the appropriate force... if you could tap VERY fast, you could keep the ball relatively motionless.

Gravity and the rope are the springs&pressure in the valve, your taps are the PWM input, and the fact that the ball (roughly) has a smooth motion despite your discrete taps demonstrates the analog output
 
   / Controlling A Hydraulic Solenoid valve With PWM #26  

DaBear3428

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PWM control of anything is achievable, you are basically turning something (motor, solenoid etc) that only has a fixed speed or position (solenoid in this case) on and off before it reaches full position or speed and repeating the process to control the speed or position of the end device. so the device is turned on and before it reaches full open it is turned off but before it closes it is opened again so it will be in a state between full open and full closed, this is done at a frequence sufficient to make it look like the device has a stable 50% (or whatever) position. This process is normally at full operational voltage unless there is a reason to do otherwise. This process depends on calibration of the PWM signal to match the the physical characteristics of the driven device and that the driven device can stand the additional stress. if the company is getting good results with their system it can work and work well in some cases. keep in mind that the driven devices may suffer reduced life, but if you are using a $30 part to sub in for a $3000 part you can afford to replace it more frequently.
 
 
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