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Thread Subject:
Simulink Compensator Design

Subject: Simulink Compensator Design

From: Vincentz

Date: 26 Feb, 2010 22:30:21

Message: 1 of 5

I am trying to tune my PID gains in Simulink 2009a.

I have a mix of discrete (controller, sensors) and continuous (plant, actuators)

When I try the Control and Estimation Tools Manager and tune my selected blocks, I get the following error:

Your Simulink model <name> could not be analyzed due to the following error:

The "zoh" method cannot be used for discrete models with poles near z=0

What does this mean? I can't find any help on this subject in the Mathworks documentation...

Subject: Simulink Compensator Design

From: Arkadiy Turevskiy

Date: 1 Mar, 2010 21:39:11

Message: 2 of 5

Hi Vincentz,
Please take a look at this demo and try changing the default zoh conversion method, as desribed in the demo. Let me know if this helps.
http://www.mathworks.com/products/simcontrol/demos.html?file=/products/demos/shipping/slcontrol/scdrateconv_codepad.html

Arkadiy

"Vincentz " <vincentz.knagenhjelm@lmco.com> wrote in message <hm9i1t$etr$1@fred.mathworks.com>...
> I am trying to tune my PID gains in Simulink 2009a.
>
> I have a mix of discrete (controller, sensors) and continuous (plant, actuators)
>
> When I try the Control and Estimation Tools Manager and tune my selected blocks, I get the following error:
>
> Your Simulink model <name> could not be analyzed due to the following error:
>
> The "zoh" method cannot be used for discrete models with poles near z=0
>
> What does this mean? I can't find any help on this subject in the Mathworks documentation...

Subject: Simulink Compensator Design

From: Vincentz

Date: 2 Mar, 2010 18:07:05

Message: 3 of 5

Thank you for the reply, Arkadiy.

The linearize command is successful in linearizing my simulink diagram, even with the 'zoh' method. Even if I could change the rate conversion method using linoptions for Matlab, I don't see how I can change the linearization options for the Control and Estimation Tools Manager, which is where I want to work. After I linearize my model in Matlab, how do I import it to Simulink's Control and Estimation Tools Manager?

Thanks for the support,

Vincentz

"Arkadiy Turevskiy" <arkadiy.turevskiy@mathworks.com> wrote in message <hmhc5u$14m$1@fred.mathworks.com>...
> Hi Vincentz,
> Please take a look at this demo and try changing the default zoh conversion method, as desribed in the demo. Let me know if this helps.
> http://www.mathworks.com/products/simcontrol/demos.html?file=/products/demos/shipping/slcontrol/scdrateconv_codepad.html
>
> Arkadiy
>
> "Vincentz " <vincentz.knagenhjelm@lmco.com> wrote in message <hm9i1t$etr$1@fred.mathworks.com>...
> > I am trying to tune my PID gains in Simulink 2009a.
> >
> > I have a mix of discrete (controller, sensors) and continuous (plant, actuators)
> >
> > When I try the Control and Estimation Tools Manager and tune my selected blocks, I get the following error:
> >
> > Your Simulink model <name> could not be analyzed due to the following error:
> >
> > The "zoh" method cannot be used for discrete models with poles near z=0
> >
> > What does this mean? I can't find any help on this subject in the Mathworks documentation...

Subject: Simulink Compensator Design

From: Arkadiy Turevskiy

Date: 2 Mar, 2010 18:22:05

Message: 4 of 5

Vincentz,
In Control and Estimation Tools Manager:
- Click on Tools menu, click on Options..., second menu item is "Choose rate conversion method" - set to ZOH by default. Change it and see if it helps.
Arkadiy

"Vincentz " <vincentz.knagenhjelm@lmco.com> wrote in message <hmjk49$j8n$1@fred.mathworks.com>...
> Thank you for the reply, Arkadiy.
>
> The linearize command is successful in linearizing my simulink diagram, even with the 'zoh' method. Even if I could change the rate conversion method using linoptions for Matlab, I don't see how I can change the linearization options for the Control and Estimation Tools Manager, which is where I want to work. After I linearize my model in Matlab, how do I import it to Simulink's Control and Estimation Tools Manager?
>
> Thanks for the support,
>
> Vincentz
>
> "Arkadiy Turevskiy" <arkadiy.turevskiy@mathworks.com> wrote in message <hmhc5u$14m$1@fred.mathworks.com>...
> > Hi Vincentz,
> > Please take a look at this demo and try changing the default zoh conversion method, as desribed in the demo. Let me know if this helps.
> > http://www.mathworks.com/products/simcontrol/demos.html?file=/products/demos/shipping/slcontrol/scdrateconv_codepad.html
> >
> > Arkadiy
> >
> > "Vincentz " <vincentz.knagenhjelm@lmco.com> wrote in message <hm9i1t$etr$1@fred.mathworks.com>...
> > > I am trying to tune my PID gains in Simulink 2009a.
> > >
> > > I have a mix of discrete (controller, sensors) and continuous (plant, actuators)
> > >
> > > When I try the Control and Estimation Tools Manager and tune my selected blocks, I get the following error:
> > >
> > > Your Simulink model <name> could not be analyzed due to the following error:
> > >
> > > The "zoh" method cannot be used for discrete models with poles near z=0
> > >
> > > What does this mean? I can't find any help on this subject in the Mathworks documentation...

Subject: Simulink Compensator Design

From: Vincentz

Date: 2 Mar, 2010 20:45:06

Message: 5 of 5

Thanks Arkadiy!

That worked! I wish the error statement was as helpful as you have been! :)

Thank you!!!

Vincentz

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