Author Topic: PVE_A_H_S compliant block threshold values  (Read 9788 times)

Brian Bandura

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PVE_A_H_S compliant block threshold values
« on: July 09, 2013, 07:49:48 PM »
Notably Sauer Danfoss moderators/tech support.

I've been running through our programs, tightening things up, looking at working values and of course questioning what some numbers mean in regards to performance and the likes.

I have been using the PVE_A_H_S compliant block for some time with an arbitrary value of 1000 for the threshold. I'm not sure where I came up with that number. Regardless, I'd like to better understand just what that value should be for the specific valves we are using. from what I understand we are using PVEH controllers on both 32 and 100 valve banks with spools selected for specific flows/function.

What baffles me is the extreme amount of data included with the function block yet nowhere can i find a table with "suggested" threshold values for specific controller/valve/spool combinations, or even a starting point for a common installation of this block. The only reference is one chart with an aritrary value of 250 used as an illustration. The actual document included with the block has 4 pages of input and output descriptions, 9 pages of how to set up inputs and outputs on a controller, which is more important??

Since this block is specific to Sauer Danfoss hardware and is meant to be used easily, why is there not a chart with "Manufacturer recomended" settings somewhere in the documentation for this particular function block? I do understand it is to offset the dead band in a spool, so that as soon as the tinyest movement is commanded the spool is pushed to the beginning of flowing. Where that is for each particular spool should be readily available.

Brian Bandura
DFI Corporation

Offline CShultz

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Re: PVE_A_H_S compliant block threshold values
« Reply #1 on: July 10, 2013, 02:12:40 AM »
Hello Brian,

Correct me if I am wrong, however the threshold on the PVEA/H/S Compliance block has very little to do with the physical PVEA/H/S.  The threshold is the deadband in the electrical input from the joystick/analog controller before acting upon the output of the compliance block sending the signal to the output pin of the controller to the PVEA/H/S coil.
So, the compliance block will not start to output a signal from the outpin to the PVEA/H/S until this threshold (deadband) is met.
Lets say your threshold is 1000 (10%).  Using a 12v analog signal the compliance block takes the 0-12v signal and converts this to a 25%-75% supply signal output.  6v is neutral, 10% threshold is 6.6v A port or 5.4v B port.  This means the compliance block will not begin to send the signal until these values are met.  Now, as far as the physical deadband on a PVG spool.. Standard progressive type spools have a 1.5mm deadband in A/B direction.  Linear type spools have a 0.8mm deadband.  This will cover a vast majority of PVG32 spools.

Brian Bandura

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Re: PVE_A_H_S compliant block threshold values
« Reply #2 on: July 10, 2013, 06:14:48 PM »

Actually, the user manual for the function block says "Sets the threshold values of Output produced by Input commands of –1 and +1."  As the input increases or decreases the function block will increase or decrease the output until the maximum or minimum value.  So this value directly offsets the output to move the spool across the physical deadband it has.

The question is, what would a good number be for this value? 

Why is there not some sort of chart with "suggested" values for specific spools?

Since this is a function block specific to a product built by Sauer Danfoss I would think it would be in everyones interest for that data to be redily available. In the user manual for the function block there is an indication that 250 is 10% of 2500 (The low value) would it not be 500 as that is 10% of the neutral value of 5000. Confusing more than enlightening.

Ah well, one day perhaps.

Brian Bandura
DFI Corporation

Offline Rafal_Typiak

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Re: PVE_A_H_S compliant block threshold values
« Reply #3 on: July 10, 2013, 09:34:55 PM »
The reason there is no 'suggested values' for the threshold of this function block is that it's a universal solution which you may tweak depending on your setup. Though I haven't really used the analog valves (just the CAN ones) but I've seen my fair share of analog signals flowing through harsh environments. As I said before - it all boils down to what exactly is your final setup.
Let's say you build a tractor. You typically start off with creating a control system for that machine in your office, on a table. Lots of room, wires separated, no external 'noise'. Now to take what you've made and put in into a newly manufactured unit. I honestly doubt you'll get the same functionality on a real life machine. Analog signals are tricky, voltage signals are even trickier. It may be enough if someone put the valve control wires next to main power cables to make your output voltage jump like it's the 80s disco era once again. That's where the threshold kicks in. You monitor how your signals behave on a machine and adjust the control system easily, without much hassle. This being said, I doubt you'll find anyone capable of telling you, what 'optimal' values of this specific threshold are for your system (considering you haven't told what it is - but regardless...). Each system is different, and each unit from the same line may (or may not be) be different. However since we're talking dead band here, I see no way of any optimization by simply tweaking the deadpans values. It depends on what you're after: execution time, more error detection, smaller program? You may cut a 1ms off if you create your own "driver" for the valves but.... you have to know what you’re doing and frankly... I doubt you'll see any real improvement. After all we're talking analog signals here - nothing more than setting up the controller's output correctly - that's all.

To sum up:
- There are no "suggested values" because it's an analog signal - susceptible to change depending on the environment.
- Using the above, 10% is definitely a good value. Change it to 0 and you'll see what will happens - your system will become jumpy.
- There are no suggested data for spools because you have different PVG units which may be equipped with different spools (5l, 10l, 100l, etc.) yet in the end this means nothing because you connect the PVG to some sort of an actuator and THAT is what influences the way the machine works. SD can't suggest what's best for any possible setup.

Best regards,
Rafa? Typiak

Brian Bandura

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Re: PVE_A_H_S compliant block threshold values
« Reply #4 on: July 19, 2013, 12:27:26 AM »
The value has nothing to do with adjusting analog signals for the environment and everything to do with moving the spool a defined amout of an offset to bring the spool to the very begining of it's flow pattern.
Each and every spool does have a "theoretical" flow start point based on a specific offset from neutral.

Just for the record, I have been involved with Plus! since the start, in fact I was using uGraph to program the terminals before they were accessable from Guide. The first JS1000 joysticks we ordered were delayed by a couple of days when it was realized they should be on different addresses to work corectly.  Prior to that we were using analog joysticks and the same Sauer valves and spools. I'm not inexperianced, just have a question.

It would be nice if someone from Sauer Danfoss, or Danfoss Power Solutions would chime in with a yes, no or no one knows answer.
It should be a fairly simple answer as the properties of the spools are quite well known. We aren't using anything exotic, simple off the shelf components.

Brian Bandura
DFI Corporation