Feedback with Transferfunctions

[SevSin99]

Dear Labview Gods out there,

I am currently working on a proof of concept for a new active vibration isolation plattform for one of the worlds best atominterferometers. As I am new to feedback control especially with labview I still do not get it to work.

My setup:

I use towo voice coil acutators to control the platform which is supposed to be isolated. For feedback I use an accelerometer which is fed via a signal conditioner in the DAQ USB-6363. From there I want to manipulate my measurement via Filter and Lag Compensators an give the Output via the DAQ USB 6363 and a VCCS to my Voice Coils which schould work against the present accelerations.

I do have the values for my filter and compensators, so I only need to implement the corresponding transferfunction to act on the measured acceleration.

In my mind it seemed pretty easy to go from a simulation to the realt time feedback, but I can not see any change to the vibration of the platform with the oscilloscope. But I am able to transfer a certain vibration frequency onto the table with my programme using a computer generated signal and putting the transferfunction to 1, so I am certain the issue must be within my VI.

Maybe you guys can spot my beginner mistakes and help me to get the set up running.

Thanks in advance.

[GerdW]

Hi sevsin,

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@SevSin99 wrote:

so I am certain the issue must be within my VI.

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And that's the reason why you didn't attach your VI!?

[SevSin99]

Seems like the upload went wrong, because the Verification failed as well.

Here it is...

[GerdW]

Hi SevSin,

you should be aware of the fact that many people (including me) don't use the latest LabVIEW version yet.

You reach a broader audience when you downconvert your VI for LV2020 or LV2019 (File->Save for previous)…

[Bob_Schor]

@GerdW,

     I was going to try to do the Save to 2020 for you, but This Isn't Ready for Prime Time (yet).  It uses multiple modules, all of which get "down-saved", and when I did it, I couldn't find where it put all of the files!  Here are some of the systems involved:

• Control Design and Simulation, 8.5
• LV 8.0 Timed Loop
• NI Analysis Library - Base (LV 2012)
• NI Analysis Library - Pro (LV 2010)
• NI Gmath (LV 2011)
• Picture Control v2
• LabVIEW Simulation Module 8.2

I've not used the CDS Module much (ever?), so there are a lot of unfamiliar LabVIEW Functions (with selectors like "SISO" and "TF and TF", but not an Error Line in sight!  There are two loops -- one a Limed Loop with a DAQmx A/D Read (1 Chan, 1 Samp) and a D/A Write (1 Chan, 1 Samp), and a second While Loop with no inputs or outputs, consisting of a Simulate Signal Express VI wired (using a Dynamic Data Wire) to the Dreaded DAQ Assistant).

@SevSin -- do you have colleagues with some LabVIEW experience that can help you get started with this Project?  Can you simplify it (a lot) and see if you can get a litle piece working?  It is worrisome (to me) to see LabVIEW code that uses standard LabVIEW functions for generating data and using DAQmx that has not a single Error Line in the code ...

Bob Schor

P.S. -- There are no LabVIEW Gods.  The much-beloved "Father of LabVIEW" has just announced a truly-earned Retirement, and will be sorely missed.

[SevSin99]

Thanks for the quick replies.

To clarifie a bit of my VI:

The untimed loop ist just to test the working of the motors and the VCCS. When I set my Transferfunktion (TF) to 1, which is the same as not having any Transferfunction at all I am able to get the Sine generated in the untimed loop read in with the DAQ and the put onto the actuators to shake my plate with this frequency.

When I change the transfercuntion to the values given Ido not see any changes of the plate and that is the part where I struggle.

@Bob_Schor

We have only limited experience with LabView in our group an absolutely none when it comes to the control and simulation package.

[SevSin99]

Here is a Version for LabView19.

[GerdW]

Hi SevSin,

thanks for converted VI, but it still misses all error handling…

• Why do you need a TimedWhileLoop (in favour of a default while loop)?
• Why don't you set a defined samplerate for the AI task when you want to run the loop at a fixed samplerate? (Keep in mind using the "1 sample" mode of DAQmxRead almost always limits you to <=100 S/s!)
• Why don't you start with a simple VI consisting just of AI & AO task and maybe a simple PID in between?

And yes: most of us don't use those toolkits that you use in this little VI…