Proportional driver card

Hi. I have a +-10V DC signal coming out of a 1756-HYD02 hydraulic servo module. I wish to control a proportional valve (Danfoss PVG32) with nominal 24V dc coils. (operate between 6 - 18V)
What is everyones most preferred amplifier driver card?

Regards Alan

This confuses me. Is this a mix and match thing? Why does the proportional valve operate between 6 and 18 volts? I thought proportional valves were linear.

Nevermind answered my own question.
http://www.tildesign.nl/int10.htm

Talking to Danfoss I was told that 6 volts - 18 volts is the min to max setting of a nominal 24V proportional coil. ie 25% voltage = 0 and 75% voltage = full.
Regards Alan Case

I couldnt locate a manual for that thing but reading the link I gave you its basically designed to work with a joystick when its in center position offers %50 of supply voltage....the 6 to 18 would make sense with a 24vdc supply. %50 would be 12volts, 25% =6volts and 75% = 18v of supply but for the device it may be 0 to full as you stated. I have worked with joysticks that worked that way.

That link is to a device specifically designed to work with that valve and plcs.

I told a fib

I did know where to find the manual: http://www.sauer-danfoss.com/domdb/SASproducts.nsf/2dd81f77829d09d086256591004f57d7/60c44569aee5bd2786256ad4006e9468?OpenDocument

I'm going to be using a card by Atos (#E-ME-AC- ...) . No choice as it comes with the hyd. package that I'm getting.

I've used one by & connected to a DeltaTau motion controller.

If you're doing positioning, check that the card has either a built in (or external connection for) dither signal to prevent sticksation of the valve.

Warning.

Which model? Don't settle for a valve that isn't meant for servo motion control. That means, no overlap on the spool and linear and quick response. I saw many models. None impressed me a meeting these requirements.

I don't think any of my customers have used a valve like like. I can recommend a valve that will work.

Hi,

I work quite frequently with PVG32 valves.

First of all it is important to understand that the valve is not working between 6-18 Volts. It is working between 25%-75% of the supply voltage. 50% is neutral. Suppose you have a powersupply that provides 22Volts. If you then give a signal voltage of 12V you will not give a neutral position instead you will get Hydraulic flow to the A port. Especially in mobile hydraulics when running on battery voltage this is important to understand since you never have 24.0V.

I am quite sure that you will have a hard time to find a controller card with a +/-10V input and 25% to 75% output to the valve. If you find one please let me know.

For industrial use we have done some tricks with 24 and 12 Volt DC/DC converters and then adding the +/-10V signal to the 12 V signal and thereby been able to generate a 2-22V signal.

For mobile use where the PVG32 is intended we are using Sauer Danfoss Plus1 controll system.

MrQ that link I posted isnt a card but it does what you mentioned.

The INT-10 is a hydraulic control component (signal converter) that converts standardized industrial control signals into the appropriate control signal for Danfoss PVG-32 proportional hydraulic valves. Danfoss valves require a control signal that is a percentage of the supply voltage. The reason for that is that the valve can be controlled by a potentiometer (joystick). The output signal of a joystick is a percentage of the supply voltage, 50% when it is in it's base position.

PLC's don't function that way. The output signal from a PLC is a standardized industrial control signal (0-10 V, -10..+10 V, 0-20 mA, 4-20 mA). The INT-10 hydrolic control component converts such a control signal into a percentage of the supply voltage. That way a Danfoss PVG-32 proportional hydraulic valve can be controlled easily by a PLC and in the appropriate way.

Click to expand...

Thanks Ron. The link you posted was the Danfoss manual which I already had but the INT-10 you mentioned in your last post was what I am after. A google search found the website. Its the same old story, theres the machine, we have a proportional valve on it already (found in the scrap heap usually), all you have to do is connect it with a couple of wires to your PLC and everything will work. Regards Alan Case

Alan,

Rexroth makes an amplifier that may satisfy your needs. It's the MDSD-2X. Here's a link:
http://www.boschrexroth.com/country_units/america/united_states/en/products/bri/Products_and_Catalogs/valve_electronics/proportional_amplifiers/index.jsp;jsessionid=YNj8PpqFRK6D856D?

Just out of curiosity, what's your application?

Kevin

Kevin. I have 2 axes.
Axis 1: Hydraulic ram with LVDT temposonic rod for position feedback.
Slow moving ram to control diameter of a pipe forming machine.
Axis 2: Hydraulic ram with LVDT temposonic rod for position feedback.
Faster moving ram but still relatively slow to position a welding head along the profiled edge of the pipe. Client fitted a Danfoss 3 bank proportional valve when a 2 bank proportional and 1 bank on/off would do the job. Also the PVG 32 is meant for joystick control as the interface module is 325 Euros each bank + 75 euros freight. I think I will convince them to swap out the valve.
Interface unit
http://www.tildesign.nl/int10_danfoss_pvg-20108182I

Regards Alan Case

Hi Peter. I will be guided by your experience on valve selections. What models do you recommend? Alan

I could give better advice if I knew more.

I need to know the flow, pressure and rates of acceleration.
Just to inform everyone I will provide an example of what I look for.

http://www.boschrexroth.com/country..._valves/a_downloads/Servo_solenoid_valves.pdf

One of my favorite valves is the Bosch NG6 and Bosch NG10. At Delta we have a NG10. I look for these features:

1. On board electronics. This is important because the electronics should be tuned to control the valve spool already. Do you AND your customer know how to tune a valve amplifier? If not then get the on board electronics. OBE.

2. Get a valve with 0 overlap. See page 4. Valves with overlap have a deadband that make position control very difficult.

3. Look for a linear flow vs control signal. Go to page 17 or 32. You should see 4 graphs. You want a flow vs control signal response to look like the upper left. This way the gain stays pretty constant regardless of flow. NEVER use a valve with flow response like the other 3. They are non-linear and will make you life miserable.

4. Go with a single stage valve if you can. In this case the the spool is moved directly with a electric coil like a speaker coil. This can be very fast. Sometimes the system pressures must be high. In this case the electronics can not supply enough force to control the spool. To get around this a pilot stage is required. When possible I like to keep the pressures below 1800 PSI so the single stage valve can be used.

5 Valves should take +/- 10 volt. You need a amplfier with most modern motion controllers to conver the +/- 10 volts to something like +/- 60 milliamps. You may need to convert the +/- 10 volts to current anyway IF the control signal must travel a long distance.

6. Go to page 18 and look at the Bode plot. For motion control purposes you should only look at the curves for +/- 100% control signal. You want to see the frequency response as flat as possible to a frequency that is higher than the frequency of motion ( acceleation ). The same goes for the phase. In this diagram one cane see that the valve is very good up to about 15 HZ. At that point the phase delay start increasing. The acceleration feed forward on the motion controller can correct for some of the phase delay and loss of gain at the higher frequencies. This valve is not really that good. For a higher performace system I like the curve flat out to a frequency that is about 10 times the frequency of motion.
If the Bode plot is not available then look at the response to full open and multiply that by 3 for an approximation of the full stroke response.

Spend a little more to get a good valve. It will pay back by being easier to tune and with quicker machine cycle times.

I have the 0811 404 803.

Thanks for the link. Very informative. I will do a bit of investigation to get some more requirements. This has been the usual where the machine builder has designed from the bottom up. They purchased all the on machine gear from whichever salesman had the best spiel, then ask to make me to make it all work together. Regards Alan Case