Tracking feedback help please!

[Evil The Cat]

I'm very new to Labview and I am looking for a bit of help, or at least to be pointed in the right direction.

I am trying to use labview + the labjack interface board to control the load from a DC generator. At the moment I have a very simple analogue out signal from the labjack feeding to some power electronics to very the load power. The analogue signal is controlled via a simple slider at the moment. I am also using the labjack to measure the power and voltage accross my load resistor BUT: I have no idea how to impliment any form of feed back.

What I want to do is measure power, vary the analogue out, measure power again and compare it to the old power. If it has gone up I want to keep changing the anaglogue out in the same direction. If the power goes down since the last power reading, I want to start moving the analogue signal in the other direction.

Basically what I need is something that can perform a simple hill climbing algorithm.

Please help as I am finding labview very hard to learn on my own.

Thanks

[Evil The Cat]

Bump, please help!

[Tom.]

Hello,

To gain feedback from previous loop iterations you can use Shift Registers. Go to the LabVIEW help and search for 'shift registers' where they are explained in detail with examples and how they can help you. You can use some sort of comparison mathematics to alter your signal generation depending on the feedback you get from your signal aquisition.

Hope this helps,

Tom
NIUK

[paulmw]

I have not heard of labjack, so I took a few seconds to look it up.  Here is a link to their website for other forum viewers...

http://www.labjack.com/index.php

You may want to specify what device you are using...

I noticed that they have a dicussions forum on the labjack web page that deals with labview.  This may be another good source for assistance too.

[Evil The Cat]

Hey, I'm using the labjack U12

http://www.labjack.com/results.php?category=2

I will look into the shift registers. Whats a good way to impliment the mathematics for comparing and altering my output signal?

Thanks

[LabJackSupport]

Sounds like you are talking about derivative control:

http://en.wikipedia.org/wiki/PID_controller

I made (and attached) a basic example that demonstrates proportional-derivative (PD) control with the LabJack U12.  It uses discrete LabVIEW arithmetic blocks for the math, but you could use a formula node if you prefer.

[Evil The Cat]

Thank you very much, I will have a go with that and see how I get on.