Custom control system with torque or voltage input

[Uxorious]

Hello,

I'm relatively new to LabVIEW and this is the first time I'll be using it for a motion application. I have a cRIO-9074 controller/chassis with a couple of NI 9514 IO modules, servomotors, and drives and what I'm trying to do is use a custom control law in my system (a sliding mode control law) to generate the signal for the motion of the motors. I've been able produce motion with NI softmotion but so far I've only been able to produce it using position, velocity, and acceleration as inputs and to tune the PID gains. What I want to do is send torque or voltage commands since the control input in my control law is torque for the motors. What I'm wondering is if this is possible with the components that I'm using right now and if someone could direct me to any useful articles or manuals that may help me.

Sorry if is a noobie issue but I've only worked theoretically with control systems so far and I've only had to simulate results with matlab prior to this. This is the first time that I've had to obtain experimental results to validate my proposed control law. Thanks in advance.

[Burrito · Accepted solution]

Hi Uxorious,

This may be possible, but since sending torque or voltage commands directly are not supported in scan mode, you will need to use your 9514 in FPGA mode.

This link describes the necessary components to run the device in FPGA mode.

You should be able to find examples in the NI Example Finder, but here is an overview of using FPGA that might be helpful as well.

[Uxorious]

Hi Burrito, 

Thanks for replying. The links that you've posted look promising. I'll definitely check them out. I have a question about FPGA mode if you don't mind. I noticed that in scan mode, the 9514 module uses PID. Am I correct in assuming that by running in FPGA mode, I am able to write my own control law in place of the built-in PID or will the 9514 still embed PID control in my motion application? I guess what I'm wondering is will FPGA mode disable the 9514's PID? Thanks again for your help.

[Burrito]

Yes, In FPGA mode the PID is disabled. Here is a link to a forum post where this is mentioned (take a look at the bottom post).

Best of luck on your application.

[Uxorious]

Thanks for your help.