Re: Error exploring a Matlab example

[James Sherman Jr.]

On Tue, Oct 21, 2014 at 2:08 PM, jmb <address@hidden> wrote:
> Hello,
>
> I am toying with a Matlab for control loop example that I found here:
>         
> http://www.mathworks.com/help/control/examples/temperature-control-in-a-heat-exchanger.html
>
> The problem is I get:
>         Gp = exp(-theta*s)/(1+tau*s)
>         error: exp: not defined for class
>
> But alternates like:
> octave>>Gp = 1/(1+tau*s)
>         Transfer function 'Gp' from input 'u1' to output ...
>                   1
>         y1:  ----------
>               21.3 s + 1
>         Continuous-time model.
>
> octave>>Gp = (-theta*s)/(1+tau*s)
>         Transfer function 'Gp' from input 'u1' to output ...
>                -14.7 s
>          y1:  ----------
>               21.3 s + 1
>         Continuous-time model.
> Do work...
>
> It appears that the exp() function is not able to handle a (Laplace
> Transform) transfer function variable.  Any ideas, thoughts or help
> would be very much appreciated.
>
> Again the relevant version info:
>         octave:2> version 3.8.1
>         octave:3> pkg list
>         Package Name    | Version | Installation directory
>         ----------------+---------+-----------------------
>                    io *|   2.2.4 | /home/.../octave/io-2.2.4
>
>         lsb_release -a
>         Description:    Ubuntu 12.04.5 LTS
>
>         uname -a
>         Linux ... 3.5.0-55-generic #82~precise1-Ubuntu SMP x86_64 x86_64 
> x86_64
> GNU/Linux
>
> Regards, JMB
>
>
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Hi JMB,

You linked to a example in MATLAB's control toolbox.  So, as a first
guess, I'd try installing the control package:
http://octave.sourceforge.net/control/
to see if that helps.

James Sherman