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Re: Error exploring a Matlab example


From: jmb
Subject: Re: Error exploring a Matlab example
Date: Tue, 21 Oct 2014 17:57:12 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2

On 10/21/2014 04:34 PM, James Sherman Jr. wrote:
> 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
>>
>>
>> _______________________________________________
>> Help-octave mailing list
>> address@hidden
>> https://lists.gnu.org/mailman/listinfo/help-octave
> 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
>
Hello James,

Thank you for your suggestion.  I am at fault for not having shown
control as being loaded, because I just copied the version information
from my previous post.  Yes I do have it loaded:

octave:1> pkg list
Package Name    | Version | Installation directory
----------------+---------+-----------------------
     actuarial *|   1.1.0 | /home/.../octave/actuarial-1.1.0
         audio *|   1.1.4 | /home/.../octave/audio-1.1.4
communications  |   1.2.0 | /home/.../octave/communications-1.2.0
       control *|   2.6.5 | /home/.../octave/control-2.6.5

and actually is loaded by default and yet I get the same error message.

Regards, JMB



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