Pid control with dancer

necyil · Nov 29, 2010

Hello All

On a wire machine use 4 stands, coiler and decoiler

St4 which is last are master. Run with Line speed
Other stands runing with Line speed and +/- 20% dancers with pid.
I have use standart siemend FB41 pid block.

Line sepeed up to 250 m/min all ok. when rich that speed Stand1 dancer start osilation.

Ob35 is 100ms and cycle of fb41 sare 100ms.
i use PI control. P gair are -1.5

any idea for solve my problem?

Best regards

nec

RocketTester · Nov 29, 2010

I don't have a good image of the plant you are controlling, but offer some basic PID concepts.

It sounds like your control loop starts a "limit cycle oscillation" under certain conditions (faster line speed).

1. Integral action tends to de-stabilize a loop, so decrease that. If units are "min", make it bigger. If units are "repeats/min", make it smaller. Not familiar w/ Siemens, but most manufacturer's PID blocks allow several equation forms.

2. Lower the proportional gain.

3. Try derivative action. That always stabilizes a loop.

You may need different PID tuning constants at different line speeds. If so, investigate "adaptive control".

For more info, buy the Process Control text by C.A. Smith and A. Corripio. Smith was my professor for several classes long ago.

L D[AR2P#0.0] · Nov 30, 2010

Decrease your sample time to 10ms

necyil · Dec 5, 2010

any advice?

Binaural · Dec 5, 2010

http://www.controlguru.com/ is often recommended here for tips on getting trickier control problems sorted. There is a lot of relatively concise information there that may help you with the specifics of tuning a tricky loop.

MichaelG · Dec 5, 2010

to me this looks like a typical web tension problem

is your PID running on fixed speed changes to the controlled stand or Percent of current speed?

mjoubert · Dec 6, 2010

If the dancer oscillates at speed or standstill, reduce the P value. (Most of out dancer controllers are set to between 0.6 and 0.9 with a I of 0.1 and a D of 0.05) This is to achieve 0-30 m/s with a machine ramp of about 20 seconds.

necyil · Dec 8, 2010

i need more advice

nec

jdbrandt · Dec 8, 2010

You could buy a Dancer Control/PID module (universal) from www.bardac.com

Honga · Dec 8, 2010

My advice: Ask a better question.

necyil · Dec 10, 2010

What is your mean HONGA??

Honga · Dec 11, 2010

Tell us what you've done I suppose. Sorry I was probably a little bit harsh.

L D[AR2P#0.0] · Dec 11, 2010

Honga said:
Sorry I was probably a little bit harsh.

No you were not - several suggestions have been made and they have been ignored from what can be seen from the resulting posts.

The OP asked for suggestions, they were given, implement them and report the results.

For example, what happened when you changed the sample time to 10ms ?

necyil · Dec 11, 2010

DearL D[AR2,P#0.0]

I was change sample time 100 to 50 ms. Now batter.

I will try with 10 ms. Your idea is batter 10ms?

Many thanks for your helps

Nec

Pid control with dancer

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