PilotPM

Hi,
I add to question too.
What difference between Cycle and Cycle_P in FB58 - TCONT_CP.
I suppose, that Cycle_P have to be time, how often is block called.
(OB35 is call every 100ms, so cycle_p=0.1 - or multiple)
I right or not? Thanks

My second question is, what is basic difference between
PID controlers FB58 - TCONT_CP an FB41 - CONT_C.
The blocks are almost the same.

Thanks for help

Marisol

Hi everyone,
I am new at forums so I hope I will make myself clear enough to get some ideas...

I am working with the FB58 "TCONT_CP" with a pulse controller. I tryed the sample projects provided in S7 and it worked perfect. Right now, I am trying to tune the controller in the instance DB58 (Options menu-->Controller tunning..), the wizard is opened and I select the "Tune by approaching the operating point with a setpoint step change" option, but when it asked for the "operating point" and the "manipulated variable difference", I'm not sure which values I should try.

I tried operationg point 70 and manipulated variable difference 80 like the PID temperature control manual proposed in its example, and I also tried lower values keeping a diference of 10 or 20 (manipulated variable difference always greater than operating point).

I haven't set to any value the CYCLE and CYCLE_P parameters, and the OB35 cycle time is 100ms, tomorrow I' going to try modifying these values, which I'm not quite sure also (I am planning to set both to 100ms as well).

I'll really appreaciate any ideas, comment, opinions and so on about this topic.

Regards,

Marisol

FB58 & FB59

PilotPM

Thanks for reply.
(of course I read manual, but not everything is clear)
But to specify it onemore time
CYCLE si multiple of CYCLE_P
CYCLE is time, how often is controler called
(OB35 is call every 100ms, so cycle=0.1)
In program (from example zEn01_13) I call controller once in OB35
and for the second time in OB1.
Is CYCLE still equal 0.1?

I ask because when I started selftune
it stoped because STATUS_H = 30005

Thanks for your work.

PilotPM

Hi,
I still have mishmash in it.
In manual everytime is CYCLE_P much less then CYCLE.
If I have OB35 calling every 100ms and Iset CYCLE=0.1
( time interval between successive call)
and CYCLE_P should be less (e.g. 0.02), then output can´t changed,
because I´m not calling FB in that time.

I´m using S7-315-2PN where in HWconfig I´m not able set cycles interruption
lessthen 100ms.

Could you write me your recomended value for Cyclic interruption, Cycle and Cycle_P.
I´m using S7-315-2PN/DP and have about 15 controllers.
(I know that every process is different)

Thans for advice.

PID_TEMPERATURE_CONT_MANUAL

Rule of Thumb for the CYCLE and CYCLE_P Sampling Times

The controller sampling time should not exceed 10 % of the calculated integral time
constant of the controller (TI): CYCLE = TI/10
For an adequately accurate manipulated variable resolution, make sure that the
following relationship applies: CYCLE_P = PER_TM/50.

Rule of Thumb for the Pulse Repetition Period PER_TM
The pulse repetition period should not exceed 20 % of the calculated reset time of
the controller (TI):
PER_TM = TI/5

I´m using S7-315-2PN where in HWconfig I´m not able set cycles interruption
lessthen 100ms.

Thanks for the interest ,

The main parameter that you should select is CYCLE that is directly related to exact sample rate of OB3X.CYCLE_P is only  a value for internal use and generating  pulse.In the attached file, monitoring the selected variables explain all you need.