[Scilab-users] Define numerator and denominator of transfer function as variables in Xcos (DLR block)

Mon Apr 3 03:04:24 CEST 2017

Hi,

Another way to represent filter in Xcos is to use the Discrete State-Space
 (DLSS) block. The matrices can be obtained directly from the
syslin representation of the system:

[A1 B1 C1 D1] = abcd(H1);
[A2 B2 C2 D2] = abcd(H2);

(This transformation can also be set in Xcos context)

Yours

2017-04-02 23:45 GMT+09:00 Tan Chin Luh-2 [via Scilab / Xcos - Mailing
Lists Archives] <ml-node+s994242n4036111h68 at n3.nabble.com>:

> you're welcome.
> anyway it should be a better way to construct the denominator, do let me
> know if you find a better way. :)
>
> rgds,
> CL
>
>
>
> On 2/4/2017 12:22 AM, Nikolay Strelkov wrote:
>
> Dear Tan Chin Luh!
>
> Thank you very much.
> It works as expected!
> The problem is solved.
>
> --
>
> *With best regards, Ph.D., *
>
>
> *associate professor at MPEI <http://mpei.ru/lang/en/Pages/default.aspx>,
> IEEE member, maintainer of Mathieu functions toolbox for Scilab
> <http://atoms.scilab.org/toolboxes/Mathieu/>, Nikolay Strelkov.*
>
> 2017-04-01 17:23 GMT+03:00 Tan Chin Luh <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=4036111&i=0>>:
>
>> Hi,
>>
>> If I understand correctly, you would like to create the filter in Scilab,
>> and directly access from Xcos?
>> if so, u could use the syslin object to do so.
>>
>> 1. Create the syslin obj
>> h1 = wfir("lp",2,[.2 0],"re",[0 0])
>> h2 = wfir("hp",3,[.1 0],"re",[0 0])
>> num1 = poly(h1,'z','coeff')
>> d = ones(1,size(h1,2)+1)
>> d(1:$-1) = 0
>> den1 = poly(d,'z','coeff')
>> H1 = syslin('d',num1,den1)
>> num2 = poly(h2,'z','coeff')
>> d = ones(1,size(h2,2)+1)
>> d(1:$-1) = 0
>> den2 = poly(d,'z','coeff')
>> H2 = syslin('d',num2,den2)
>>
>> 2. In Xcos
>> use H1.num in the numerator block for LPF, H1.den in the denominator for
>> the LPF, same for the HPF.
>>
>> Hope this helps.
>>
>> rgds,
>> CL
>>
>>
>> On 1/4/2017 9:53 PM, Nikolay Strelkov wrote:
>>
>> Anybody?
>> Dear Tim, do you have any idea?
>>
>> --
>>
>> *With best regards, Ph.D., *
>>
>>
>> *associate professor at MPEI <http://mpei.ru/lang/en/Pages/default.aspx>,
>> IEEE member, maintainer of Mathieu functions toolbox for Scilab
>> <http://atoms.scilab.org/toolboxes/Mathieu/>, Nikolay Strelkov.*
>>
>> 2017-03-23 14:27 GMT+03:00 Nikolay Strelkov <[hidden email]
>> <http:///user/SendEmail.jtp?type=node&node=4036111&i=1>>:
>>
>>> Dear all!
>>>
>>> I'm playing with simple digital filtering in Xcos 5.5.2.
>>> I have two filters - low-pass and high-pass, connected in series.
>>>
>>> Xcos does not have convolution block.
>>> So I write FIR transfer function
>>> <https://ccrma.stanford.edu/%7Ejos/fp/FIR_Transfer_Function.html>
>>> manually from impulse response function.
>>> I get impulse response functions from wfir function.
>>>
>>> Let's assume that we have two simple filters with impulse responses:
>>> h1 = [0.3741957    0.3741957]; // it's low-pass filter from h1 =
>>> wfir("lp",2,[.2 0],"re",[0 0])
>>> and
>>> h2 = [- 0.1870979    0.8  - 0.1870979]; // it's high-pass filter h2 =
>>> wfir("hp",3,[.1 0],"re",[0 0])
>>>
>>> I convert them to DLR
>>> <https://help.scilab.org/docs/5.5.2/en_US/DLR.html> SISOs and get:
>>> H1(z) = 0.3741957*z^-1 + 0.3741957*z^-2 = ( 0.3741957*z + 0.3741957 ) /
>>> (z^2);
>>> H2(z) = -0.1870979*z^-1 + 0.8*z^-2  - 0.1870979*z^-3 = ( -0.1870979*z^2
>>> + 0.8*z  - 0.1870979*z ) / (z^3);
>>> and place their numerator and denominator to the corresponding DLR
>>> blocks.
>>> Model is in attachment. It's an illustration, not real world example.
>>>
>>> I have a question. How I can automate the aforementioned process
>>> programmatically?
>>> I tried to create numerator and denominator with poly function and as
>>> strings, but Xcos does not support these types in DLR settings.
>>>
>>> --
>>>
>>>
>>>
>>>
>>> *With best regards, Ph.D., assistant professor at MPEI
>>> <http://mpei.ru/lang/en/Pages/default.aspx>, IEEE member, maintainer of
>>> Mathieu functions toolbox for Scilab
>>> <http://atoms.scilab.org/toolboxes/Mathieu/>, Nikolay Strelkov.*
>>>
>>
>>
>>
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