Why MotionView UserSubroutine "sysfnc" returns all 0?

Garand · 2025-06-20T10:03:00+00:00

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Hello everyone,

I used a SYSFNC Subroutine in my Python subroutine script, for reading some system state values. The usage are showed below:

`USER({m_mp_dth.idstring},{m_mw_dth.idstring})`

def CNFSUB(id, time, par, npar, loci, ni, locj, nj, gap, gapdot, gapdotdot, dflag, iflag):   
ipar = [0]*3    
ipar[0] = int(par[0])    
ipar[1] = int(par[1])    
ipar[2] = int(par[1])    
[dw, err] = py_sysfnc("DY", ipar)  # mP_dth, mW_dth, mW_dth [70000094, 70000093, 70000093]    
py_errmes(err, "Error calling SYSFNC for DY, dw", id, "STOP")    
print("DY -- dw=%r, err=%r" % (dw, err))
…
return …

I made a print for debugging, and all the print is:

DY -- dw=0.0, err=0

Seems the sysfnc returns 0 correctly. But i also made a output for the same system state:

DY({m_mp_dth.idstring},{m_mw_dth.idstring},{m_mw_dth.idstring})

The output curve in HyperGraph do has a value, shows below:

Why did SYSFNC not read those data? Is the problem in my scripting or defining the input parameters for USER()?

Could anyone help me out on this?

Sincere gratitude,

Garand

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MotionView/MotionSolve

v2021

Accepted answers

Orestis_YB

Hello @Garand,

you could maybe workaround that. Try to use a GFOSUB and store the sysfnc results in global variables. Then you may be able to access those from the CNFSUB.

Hope this helps!

Best regards,
Orestes

All comments

Garand

Well, I've tried in GFOSUB and MOTSUB, by add codes below in the first line of function:

[dw, err] = py_sysfnc("DY", [70000094, 70000093, 70000093])

print(dw)

Both of them print the dw value correctly, but still all 0 in CNFSUB.

Why does it happens? What can I do if I need to use it in CNFSUB?

Orestis_YB

Hello @Garand,

as for the CNFSUB and MOTSUB, SYSFNC is not supporter there. Can you maybe share the model that you are using SYSFNC within GFOSUB and it doesn't work?

Best regards,
Orestes

Garand

Hello Orestes,

Thank you for the reply. In fact, SYSFNC works well in my GFOSUB script. But I have trouble in using it in CNFSUB. Now the main point confuse me is how to achieve the same function as SYSFNC in CNFSUB. That is, read the system state data in the simulation process, and use these data to calculate parameters in the script.

Specifically, my CNFSUB script expects to calculate the contact stiffness by using the input relative displacement.

Could you please give some relevant suggestions?

Sincerely,
Garand

Orestis_YB

Hello @Garand,

from what I understand you want to use the relative displacement of the bodies in contact. Would GAP and GAPDOT attributes work for you then?

These are the ones used by the example script as well.

Best regards,
Orestes

Garand

Hello Orestis,

Thanks for the reply. I want to use the relative displacement of the two body, it may infect contact property such as stiffness. So GAP may not fulfill the need. I have to rely on sysfnc results.

Can I manage it by call another sysfnc-supported -SUB in CNFSUB, and make it returns result from sysfnc? Or if I have to define a new subroutine (with Sobroutine Builder maybe?) to realise this function?

Thank you for the attention again.

Garand

Orestis_YB

Hello @Garand,

you could maybe workaround that. Try to use a GFOSUB and store the sysfnc results in global variables. Then you may be able to access those from the CNFSUB.

Hope this helps!

Best regards,
Orestes

Garand

Hello Orestes,

I tried the method in your reply, and it works!

Thank you so much, it helps me a lot.

Best wishes

Garand