[scilab-Users] transfer function, z^-1 form

[Sumit Adhikari]

Certainly,
Try as in following :

num = [0 0.38 0.31]
den = [1 -0.86 0.55]

Hfilt      = poly(num,'z','c')/poly(den,'z','c');

[hfilt,fr] = frmag(Hfilt,1024);

......... and then the story you want to build .................

Let me know if it helps.
Regards,

Sumit




On Fri, Feb 26, 2010 at 4:04 PM, David PICARD <
d.picard at opgc.univ-bpclermont.fr> wrote:

> Ooops, sorry, you're right. I mistyped the denominator (0.86z^-1 instead of
> -0.86z^-1) . Of course, I was confused by the weird step response...
>
> Is it possible to specify the transfer function with polynoms ? In this
> case, it would be something like :
> num = [0 0.38 0.31]
> den = [1 -0.86 0.55]
>
> Regards.
>
>
> Collette yann a écrit :
>
>
>> For me it corresponds to the good transfert function:
>>
>>    0.31 + 0.38z                    z^2* (0.31*z^-2 + 0.38*z^-1)
>>  ----------------         =       ------------------------------------
>>  0.55 + 0.86z + z ^2            z^2*(0.55*z^-2 + 0.86z^-1 + 1)
>>
>> Scilab seems to have simplified in a way your transfert function
>>
>> YC
>>
>>
>> David PICARD a écrit :
>>
>>> I need some help to define the following transfer function :
>>>
>>>  0.381417 z^-1 + 0.310306 z^-2
>>> ---------------------------------
>>> 1 - 0.857089 z^-1 + 0.548812 z^-2
>>>
>>> This is a 2nd order system : w0=1, Damp=1.3, Gain=1.0, Te=1s
>>>
>>> I tried :
>>> -->z=%z;
>>> -->sys=syslin(1.0,(0.38*z^-1+0.31*z^-2)/(1+0.86*z^-1+0.55*z^-2))
>>> sys  =
>>>
>>>     0.31 + 0.38z
>>>   ----------------
>>>                   2
>>>   0.55 + 0.86z + z
>>>
>>>
>>> But it NOT what I asked !!! Help !
>>>
>>> It is so straightforward with GNU Octave, that I am really frustrated !
>>>
>>>> sys=tf([0.000000 0.381417 0.310306],[1.000000 -0.857089 0.548812],1.0);
>>>> step(sys)   // shows the oscillating, stabilizing step response
>>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>


-- 

--------------------------------------------
Sumit Adhikari
System Design Engineer
austriamicrosystems AG
Business Unit : Automotive
Mob : 00-91-9885271710/00-91-9000161710
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