Mechanical-testing Closed-loop system in DASYLab

[Kiko-of-Brasil]

Looking to create a closed-loop system in DASYLab.

Experiment involves single-point bending tests on UHPC (concrete) simply-supported beams.  As load is increased (hydraulics are pushing down) beam will crack.

I need the loop to assure me that these beams will crack at a constant rate; I will be measuring crack width.

Using the crack-width/time I need to control the rate of displacement of the hydraulics; e.g.: if the beams are cracking too fast, I need to slow the hydraulics down...and vice-versa.

I am thinking the solution is via the PID module but I am having a hard time understanding the module parameters and also the possible worksheet layout.  The hydraulic testing machine to be used is the MTS 810.

Thanks in advance.

Kiko

[TomRizzo]

Kiko,

for this kind of testing, DASYLab is not suggested because the PID loop is not reliable for closing loops in Hydraulic.

I would suggest to close the loop with the MTS controller and use DASYLab to generate the signal and collect the data.  A testing servo-controller provides you with all the tools needed to control and limit the test.

A computer based system would not provide the safety required for this kind of testing.

We actually created DASYLab drivers for our system, Lynx, for that reason.

[MHa]

Kiko,

the MTS 810 means this test system? -> http://www.globalspec.com/FeaturedProducts/Detail/MTSSystems/Material_Testing_System_MTS_810/57319/0

or this? -> http://www.upc.edu/pct/documents_equipament/d_77_id-412.pdf -> " ... Programming Libraries include drivers for LabVIEW, Visual Basic, and C++ programming environments to assist you in developing customized test applications ..."

Best regards,

MHa

[TomRizzo]

Matthias,

Yes it is and usually to close the loop on a servo-hydraulic system, it requires at least a 4 or 5 KHz loop speed.

Tom

[MHa]

Understand Tom - is this not a job for DASYLab Microstar DAP http://www.mstarlabs.com/ driver with an useful DAP device?

[Kiko-of-Brasil]

yeah, that's the system.  attached you'll see a pix of ours including one of our tested samples.

thanks, kiko

[Kiko-of-Brasil]

i'll see about using TestStar (MTS software) to run the loop.  i can see me having a little more control but the software gives me the creeps when compared to DASYLab or MATLAB, which we have around.

i usually use DASYLab to send the signal to the 'hydraulic controller' because of the easier correlation with the data collection.  DASYLab has been great.

it seems to me that since i am collecting a signal (crack width) that will eventually control the ram/hydraulic displacement rate, that DASYLab was the way to go for everything.

kiko

[TomRizzo]

You are right.  If you use the MTS controller to only close the loop and use DASYLab to generate the command and do the analysys you will be OK and it will work great.

Also, look at ricardo.tanaka@lynxtec.com.br in case you want to upgrade the MTS

[MHa]

OK Tom, you means the MTS + http://www.lynxtec.com.br./engl_index.htm + DASYLab is the best Easy To Use package for the user?

[MHa]

Kiko, do you have found a link for the MTS info "... Programming Libraries include drivers for LabVIEW, Visual Basic, and C++ programming environments to assist you in developing customized test applications ..."? I can't find this on MTS page, it would be helpful to see which API functionality is included into these libraries.