Before I can graduate I have to do a final project . The project that I choose involves upgrading the control system of an old sterilization machine using an ab contrologix 5000 . I already received some of the documentation from the machine but the most important documents have alot of important stuff missing, an example of this is that there is no document that outlines what all the variables that modify the documented phases mean, asside from the ones I can find in the process and instrumentation diagram (RTD,s selenoids etc).

Since I have no experience controlling temperature and all my knowledge lies on undergraduate control theory, I am hoping for advice on anything I should worry about, any books or specific topics I should read up some more, etc.

I also have some questions like :

What would be the best way to implement and tune the PID gains (kp, ki, kd) if I don't have the transfer function for the system ( building up the transfer function of the system is out of the question since that would be a end of career project itself) ?

should I use the old PID command or the PIDE?

As I said before any advice will be welcome! (heh I want to graduate on 2008 :) )

I'll jump in and stick my neck out before Peter Nachtwey gives his advice...
Check out the site www.controlguru.com
You will find some straightforward info on how to approximate the transfer function of your system and use the results to set tuning parameters.

Also search the PLCS.net forum for threads on the same subject from about a year ago.

Your system will most likely fit a first order plus deadtime model which you can easily simulate on the ControlLogix using function blocks. You can also run PID control against the simulated model and trend the results using just the CLX processor and RSLogix5000.

PID instruction uses a position algorithm
PIDE instruction uses a velocity algorithm