labview feedback on-the-fly

[cell]

I am a student working on my senior design project and I have run into a problem. I am using LabView 7.1 and NI-DAQmx software with the USB-6008 DAQ.
The goal is to create a LabView code which:

1. Reads a voltage from a force sensor
2. Compares the voltage to a user input value
3. On-the-fly calculation of the difference of the voltage
4. Using the difference to send analog signal to remote control power supply (Aerotech Soloist-20) which in turn moves the linear motor to approach zero voltage difference.

Which Express VI's are important to examine and does anybody have any hints or suggestions on how to attack this problem?

Gerardo

[cell]

I incorrectly stated NIDAQmx software. I am actually using NI-DAQmxBase 1.4

[DavidT]

Hi Cell
This sounds like you need a simple PID controller.
If you look at the shipped examples and search for PID, you will find a number of PID demos which you can modify to suit. I suggest you look at the DAQmx 'PID Control - Single Channel'.
Just ensure that you start with a low Proportional setting and have your finger on the power button before starting. Depending on the system response you are after, slowly increment your Proportional Gain until you are satisfied.
Let me know if you have any other questions.

p.s. Im not sure what is packaged with Daqmx base, but hopefully these examples will be available.

[cell]

Thanks for the info, but I was instructed to uninstall DAQ-mx, because it is not compatible with USB-6008. I don't have the PID examples to work from.

Gerardo

[DavidT]

Regardless, there should be some PID examples that work with Traditional Daq.
I have attached a simple pid example for you to look at.