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Thread Subject:
Problem with PID Tuner in MATLAB 2010a

Subject: Problem with PID Tuner in MATLAB 2010a

From: Lalit Kumar

Date: 20 Oct, 2010 09:20:04

Message: 1 of 3

Hello everyone!
I am designing a PI Controller for a multilevel inverter. The controller is connected in the actual circuit (and not on transfer function blocks of it).
My problem is that whenever I try to tune my controller following ERROR MESSAGE appears:
"Linearization aborted because the linear plant model seen by the PID block is effectively 0. Ensure the PID loop is physically closed and none of the blocks in the PID loop return 0 when linearized at time t = 0"

I 'm badly caught with this problem and will be grateful if someone can help me to get out of it.....
Thanks in advance...

Subject: Problem with PID Tuner in MATLAB 2010a

From: Steven_Lord

Date: 20 Oct, 2010 13:32:32

Message: 2 of 3



"Lalit Kumar" <lalitsahu9@gmail.com> wrote in message
news:i9mc84$ho2$1@fred.mathworks.com...
> Hello everyone!
> I am designing a PI Controller for a multilevel inverter. The controller
> is connected in the actual circuit (and not on transfer function blocks of
> it).
> My problem is that whenever I try to tune my controller following ERROR
> MESSAGE appears:
> "Linearization aborted because the linear plant model seen by the PID
> block is effectively 0. Ensure the PID loop is physically closed and none
> of the blocks in the PID loop return 0 when linearized at time t = 0"
>
> I 'm badly caught with this problem and will be grateful if someone can
> help me to get out of it.....
> Thanks in advance...

Well, _is_ the PID loop physically closed? _Do_ any of the blocks in the
PID loop return 0 when t = 0? Only you can answer these questions, since
only you have access to the model. [And no, please do NOT send me the
model.]

--
Steve Lord
slord@mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
To contact Technical Support use the Contact Us link on
http://www.mathworks.com

Subject: Problem with PID Tuner in MATLAB 2010a

From: Arkadiy Turevskiy

Date: 20 Oct, 2010 15:45:05

Message: 3 of 3

"Lalit Kumar" <lalitsahu9@gmail.com> wrote in message <i9mc84$ho2$1@fred.mathworks.com>...
> Hello everyone!
> I am designing a PI Controller for a multilevel inverter. The controller is connected in the actual circuit (and not on transfer function blocks of it).
> My problem is that whenever I try to tune my controller following ERROR MESSAGE appears:
> "Linearization aborted because the linear plant model seen by the PID block is effectively 0. Ensure the PID loop is physically closed and none of the blocks in the PID loop return 0 when linearized at time t = 0"
>
> I 'm badly caught with this problem and will be grateful if someone can help me to get out of it.....
> Thanks in advance...

Hi Lalit,
The way PID Tuner works is that it linearizes your nonlinear Simulink model and then designs a PID controller for the obtained linear system. If your Simulink model has discontinuities or triggered or enabled subsystems you may get zero linearization and get the message you are seeing. This will also happen if you have PWM in your model.

There are a couple of things you can do:
1) In Release 2010b we enhanced the PID Tuner. Now if you model linearizes to zero, the PID Tuner will ask you to provide a linear model You can import one from MATLAB workspace or try to relinearize your model at a certain simulation snapshot time.
There is a nice demo in 10b showing exactly this:
http://www.mathworks.com/products/simcontrol/demos.html?file=/products/demos/shipping/slcontrol/scdenginectrlpidpad.html

If you can upgrade to 10b, then do that and follow the workflow in the demo.

2) If upgrading to 10b is not possible for some reason, then please read this section of 10a documentation and follow the recommendation there:

http://www.mathworks.com/help/releases/R2010a/toolbox/slcontrol/ug/br684zf.html#bsgrodj-1

Hope this helps.
Arkadiy

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