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Thread Subject:
model based controller for controlling interpolation (table lookup) system

Subject: model based controller for controlling interpolation (table lookup) system

From: Jean Thomas

Date: 26 Feb, 2010 14:00:21

Message: 1 of 4

Dears,
I have a system wich based on interpolations (lookup tables), so that the outputs are computed directly from the inputes with the ''interpn'' function.
Do any one have experiance or idea how to develope a linear model for this system, in order to use model based controller technique to control it?
Thanks in advance.

Subject: model based controller for controlling interpolation (table lookup) system

From: Jean Thomas

Date: 26 Feb, 2010 14:36:03

Message: 2 of 4

"Jean Thomas" <jhh_thomas@yahoo.com> wrote in message <hm8k5l$65v$1@fred.mathworks.com>...
> Dears,
> I have a system wich based on interpolations (lookup tables), so that the outputs are computed directly from the inputes with the ''interpn'' function.
> Do any one have experiance or idea how to develope a linear model for this system, in order to use model based controller technique to control it?
> Thanks in advance.

Another question related or may be equivelant to the previous one:
Is the ''interpn'' function can be reversed?? meaning that if I know the outputs (the required outputs) and of course the lookup-tables are given, Could I know or caluculate the inputs??

Subject: model based controller for controlling interpolation (table lookup) system

From: Arkadiy Turevskiy

Date: 1 Mar, 2010 22:31:22

Message: 3 of 4

Just like with any other nonlinear model, you will need to find an operating point where you want to design your controller and then linearize your model around that operating point.

To see how to do this, take a look at Simulink Control Design demos:
http://www.mathworks.com/products/simcontrol/demos.html

Look at the ones that have "trim" and "linearize" in the name.
HTH.
Arkadiy

"Jean Thomas" <jhh_thomas@yahoo.com> wrote in message <hm8k5l$65v$1@fred.mathworks.com>...
> Dears,
> I have a system wich based on interpolations (lookup tables), so that the outputs are computed directly from the inputes with the ''interpn'' function.
> Do any one have experiance or idea how to develope a linear model for this system, in order to use model based controller technique to control it?
> Thanks in advance.

Subject: model based controller for controlling interpolation (table lookup) system

From: Matt J

Date: 1 Mar, 2010 22:44:08

Message: 4 of 4

"Jean Thomas" <jhh_thomas@yahoo.com> wrote in message <hm8m8i$nl7$1@fred.mathworks.com>...
> "Jean Thomas" <jhh_thomas@yahoo.com> wrote in message <hm8k5l$65v$1@fred.mathworks.com>...
> > Dears,
> > I have a system wich based on interpolations (lookup tables), so that the outputs are computed directly from the inputes with the ''interpn'' function.
> > Do any one have experiance or idea how to develope a linear model for this system, in order to use model based controller technique to control it?
> > Thanks in advance.
>
> Another question related or may be equivelant to the previous one:
> Is the ''interpn'' function can be reversed?? meaning that if I know the outputs (the required outputs) and of course the lookup-tables are given, Could I know or caluculate the inputs??
==================

Assuming you are linearizing over a region where the input-outputrelationship is montonic, you can reverse interpn by doing

x=interp(y),

instead of

y=interp(x)

If it is not montonic, the inversion is ill-defined.

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