Reflow Tuning Parameters

Reflow Tuning Parameters

Postby Maddox » Sun Apr 29, 2012 11:24 pm

I had a chance to lengthen the ramp times to see how well the PID parameters are working for my set up. Here's the test profile:

Code: Select all
Madtst
3, 100, 0      //step (3) setpoint to (100)
2, 0, 0         //wait (2) until it crosses the setpoint
1, 200, 300  //ramp (1) to 200 over 300 seconds
2,0,0           //wait (2) until it crosses the setpoint
1, 250, 200  // Now ramp to 250 over 200 seconds
3, 0,0          // End


The PID settings are the default:

KP = 2.0
KI = 0.5
KD = 2.0

Here is the result:

http://www.flickr.com/photos/77705680@N06/6980153500/

I confess to being unsure of which parameters affect what behavior at the moment, but I am pretty sure it can do better with some tweaking. Any suggestions on where to start?
Maddox
 
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Re: Reflow Tuning Parameters

Postby Brett » Mon Apr 30, 2012 1:02 am

@Maddox I hope you don't mind me moving this to it's own topic. this is more of a tuning question than a profile question, so I pulled it from that topic.

as far as the tunings, your instinct is correct. it should be possible to remove, or at least diminish those oscillations. these are likely caused by:
-too much integral action (Ki), and/or
-too much overall oomph (technical term) of the controller (Kp, Ki, Kd)

to specifically reduce the integral action, lower only the value of Ki. to reduce the oomph (tm,) reduce all 3 parameters by an equal percentage.
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Brett
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