PXI RT Controller with DAQ for real-time control

[servo]

I am designing a new real-time control system. My application requires 1 analog input, 2 encoder inputs and 1 analog output output per axis. I need 20 axis PID controller that can handle such inputs/outputs with 300 Hz PID update rate. PID algorithm will read 1 analog input or 2 encoders to compute and output servo command (1 analog command) per axis. The axes are independently controlled.

After reading your materials in your web-site, it looks like that the Embedded Real-Time Controller PXI-8145 RT with LabVIEW RT software can handle my applicaion with A/D, D/A and counter board. Please consider the following configuration of mine and get me your opinion/quotation.

1. 1x PXI-8145 RT (PXI Embedded Real-Time Controller)
2. 1x PXI-6254 (M series multu-function DAQ with 32 channel A/D)
3. 1x PXI-6723 (32 channel D/A Board)
4. 5x PXI-6602 (32-bit, 8 channel Timer/counter board)

You can recommend other low-cost 16-bit Timer/counter board because I need just 16 bit counter.

With the above configuration, I would like to know if PXI-8145 RT can handle my application. 300 Hz PID update rate is very slow compared to modern industial application, so I assume it can handle my application.

Someone say I will need another Motion controller like PXI-7358 to handle my application. I wonder I need the motion controller in my application. I don't know what the role of the motion controller is compared to the PXI-8145 RT.

[GValdes]

Hello, Servo,

Thanks for describing the type of hardware you are planning on using. From the requirements of the system, you should be able to get 300 Hz PID loops using the PXI-8145. This controller is spec'd to do a single PID loop at 6 kHz; obviously, as the channel number increases, the speed will decrease, but for the number of channels that you will have (20 analog inputs/20 analog outputs) the rate will still be above 300 Hz. The way I'm thinking you will do it is by using the PID or PID Advanced VI, and just connect the array of analog inputs, setpoints, and PID gains, and the VI will give you the array of outputs. I will definitively recommend you using the NI-DAQmx driver to do the acquisition because it is easy to use; however, this driver takes more hard disk space and memory than Traditional DAQ, so I will encourage you to get the PXI-8145 with the memory and CompactFlash upgrades (at least 64 or 128 RAM, and 64 or 128 CF).
So, from the system capabilities, you should be fine. However, it will be great if you could describe what are you trying to achieve. Are you planning on controlling some motors? If you describe a little bit your application, people from other deferments within NI or other users should be able to give some suggestions and determine if an 8145 will all the DAQ boards will be a good solution, or if a PXI-7358 will do the trick even better.

I hope this helps!

GValdes
Applications Engineering