Regulating to a position with PLC and DC-motors

Hi,

I have an S7 CPU, 2 DC-Motors and 2 position sensors (0-20mA).

How can I regulate to the integer value 22318 for example.

Now I do that with compare functions and a dead band for stopping at a certain point.

Is there a better way to regulate ?

what type of DC drives u r using?

u can use a PID command and a deadzone.

Hello Combo;
If you are using the word "regulate", I presume you would want to maintain your DC motors at a setpoint of speed, for example. I would look into a PID function.
What CPU are you using?
A s7-200 has a PID wizard that will allow you to "fill in the blanks" and build code for the regulation blocs.
A S7-300/400 has FB41 "Cont_C" available, very powerful and flexible, but it requires a little study. There are many posts on this forum on this subject, look at them first, then come back to us for more questions.
Hope this helps,
Daniel Chartier

Pid Block

Hey,

I've seen the PID block FB41 before. But never used it. I allready did a project with the same problem, operators set a value from 0 to 100% on a Panel, 100% = 27648 Integer. So The motors also had a constant speed and I also controlled the motors with just start/stop.

I didn't use the FB41 back then, I wrote something myself. A Smooth of the analogue measured value to make the signal less unstable, and compares with a dead band. The stop was with a off delay, so the stop signal came a bit to soon, but the off delay made it stop in the right position. AFter the stop, the system may not regulate, it is just going into position and done.
So this worked, but, to complex.

I'll try FB41; it's a good idea. The Deadband and Smooth isn't needed then I think, btw, anyone used the smooth in the hardware ? Works fine ?

Algoritme

PID's use allgoritme's, anyone know how to write such thing ?