[ATR401] Description of the algorithm of PID

[user2366]

hello
can you send me the algorithm how the pid works at the ATR401 controller when i change proporional band, integral time and derivative time so i can better adjust the controller.
thx

[Pixsys tecnico 1]

Hi,
to set PID parameters correctly you haver to know that:
-[P.b.] is the process inertia in degrees: eg. if your setpoint is 100 and the process increases until 110 you have to set P.b. as 10.
-[t.i] is the process inertia in seconds: eg. if your setpoint is 100, the process will increases until 110 employing a certain time. This time is the integral time.
-[t.d] is normally 1/4 of the integral time.

Try to set this parameters start with all set to zero, then set P.b. and see how the process reacts. The set the integral time and see how the process reacts. Last, try to set the derivative and see how the process reacts.

This is the right way to set PID parameters but, the EASY WAY is to use autotuning

[user7736]

Hi,

but if after the Auto Tune we see, that the system reacts to slow on the change of temperature.
Which parameter is better to change, to make it work faster?

For example: DRR245
Setpoint: 96C
Output: 4...20mA to Inverter.
Control: PID

Problem:
It`s start to change the output only, when temperature is again lower then 93?
Is it possible to change some parameter in some direciton, to get ir work more accurate or react faster?

Thank you.

[Pixsys tecnico 1]

Set [Tune] to "diS" then reduce [P.b] of an 20% of its value.

[user7736]

HI,

we have DRR245 controller with PID control on motor controlled valve. (1 relay opens, second closes the valve!)
And after autotuning, it shakes around the setpoint, but its not holding the setpoint (in attachment picture!)
IT feels like, it reacts to slow, when process value starts to rise and get closer to setpoint, DRR closes the valve to less (It gives just small impulse ~1 sec, to close the valve, and the process value goes up faster, as controller closes the valve.
(I think in good conditions DRR after the process value starts to rise and go closer to setpoint closes faster the valve and that stops the process value to go up)
Here is some parameters:

18. Proportional band= 1
19. integration time 5,9
20. Derivation band 1,4
21. Cycle Time 60 (From valve full open-close time)
52. Dead band -0,1​

What to change, to get it faster to react to process value changes?

[Pixsys tecnico 6]

Hi,
you can to try to check this DRR parametrs:
54.[c.FLt.]--> Conversion Filter
55.[c.Frn.]-->Conversion Frequency

Or you can try change the 57[S.d.t.u.] parameter and after you can to do again the Autotuning.

Best Regards

[user7736]

Hi,
here is parameters:
54.[c.FLt.]--> Conversion Filter = 15 samples Mean
55.[c.Frn.]-->Conversion Frequency =16,7 Hz

But maybe we need to change some PID parameters, so it response faster? (When the process value reacts, faster closes or opens the valve? )

In which direction to change 57. parameter?

[Pixsys tecnico 6]

Hi,
you can try to reduce the value of the paraemter 54. Then you can to restart the Autotuning. If you reduce the value of the parameters 54 the ATR is more fast to read the probe value but less accurate.(less average value).

If you want to change the PID value, you must know the PID value of your application: for example, the smoller is the proportional band [Pb], the more the PID is similar to an ON / OFF...

Best Regards