How to simulate 7350 control using Simulation toolkit

[Dr_Laine]

I am running a linear DC motor through PXI-7350 and would like to simulate the operation using Simulation toolkit. My basic concerns are:

1) Plant Simulation. I am modeling the linear motor as a simple frictionless mass by my''=F
I think this should be no problem.
2) Controller Simulation. I am not sure if the axis tuning parameters apply to the velocity loop or position loop. If I command a trajectory profile (position-based or velocity-based), how is this interpreted by the board (converts always to position profile or to velocity profile)? How is it controlled, only position controlled by encoder? Or is there instead a derived velocity which is controlled? I think these tuning parameters are for the velocity loop and I control position from within my LabVIEW code.
3) DAC Output. What is the full-scale for this output? For example, does +10V out correspond with the maximum velocity as set in MAX? I think this is a 16-bit DAC for my 7350.

Has anyone done NI-Motion simulation and can point me to simple block diagrams or basic simulation code?

Thanks,
Laine

[Dr_Laine]

Update:

1) I still think this model is ok (may add damping later)

2) Servo PID in MAX is POSITION control with
- position error integral scaled by 1/256
- position error derivative calculated every Td periods (but Kd gain is applied every period with the most current derivative value - is it correct?)
So there is no velocity loop?

3) This is a 16-bit output, but I still don't understand what full scale (+32767) represents. Is the value just whatever it turns out to be (based on the gains used) then saturated to +32767/-32768? Or is the physical representation defined by the downstream amplifier (for instance, +10V into my drive represents peak motor current out)?

Thanks for any information. I am starting to get meaningful simulation results with the Simulation toolkit.

[Jochen]

Laine,

there is already a software implementation of the NI motion controllers available. The NI SoftMotion Development Module for LabVIEW provides a trajectory generator, a spline engine and control algorithms that are almost exactly the same as the control algorithms on the NI motion boards.

I know this is not the exact answer to your questions but on the other hand as there is already a good solution available there shouldn't be the necessity to reinvent the wheel.
If this module is not an option for you please let me know and I'll try to find answers for your questions.

Best regards,

Jochen Klier
National Instruments Germany