01-20-2016 12:57 PM
Hello, colleagues.
I have response function (RF, see pic.) of some part of a linear system in form (input/output)/frequensy or I can represent this function by real, imaginery at frequency. I need to delete this part from a full model and represent it by submodel from signal library.
What submodel from sygnal library I shoud use to represent this deleted part? I tried to use dynamic response function submodel but it doesnot fit well to my RF. I heard it is possible to use real and imaginery parts of RF, but i cant fined appropriate submodel in signal library. Please help me.
01-21-2016 06:22 AM
Hi Vitalii,
in LMS Imagine.Lab Amesim you have the possibility to import linear models (menu Modelling > Import linear model in sketch mode).
The supported files types are:
>> help tf2ame TF2AME Save transfer function in an external file readable by AMESim Save transfer function : NUM(s) H(s) = -------- DEN(s) in an external file readable as an AMESim special submodel. NUM and DEN must contain the coefficients of the numerator and denominator in descending powers of s TF2AME(NUM,DEN,'FILENAME') save transfer function in file FILENAME TF2AME(NUM,DEN) without third argument the default file name is TRANSF.ssp See also ss2ame, ameloadj, fprintf, control system toolbox >>
>> help ss2ame SS2AME Save state space matrix system in an external file readable by AMESim Save State-space system : . x = Ax + Bu y = Cx + Du in an external file readable as an AMESim special submodel. SS2AME(A,B,C,D,'FILENAME', X) save state-space matrices A,B,C,D in file FILENAME along with the values of the state variables X. SS2AME(A,B,C,D,'FILENAME') save state-space matrices A,B,C,D in file FILENAME. SS2AME(A,B,C,D) without fifth argument the default file name is STATSP.ssp. See also tf2ame, ameloadj, fprintf, control system toolbox.
Best regards
01-21-2016 11:01 AM
Thank you for your support.
But I think first what I have to do the interpolation of that transfer function (see pic. above) into two polinominal functions. After that i will have all coefficients wich I shoud to put into ft2ame function. I am right?
01-21-2016 11:04 AM - edited 01-21-2016 11:24 AM
vitalii wrote:
Thank you for your support.
But I think first what I have to do the interpolation of that transfer function (see pic. above) into two polinominal functions. After that i will have all coefficients wich I shoud to put into ft2ame function. I am right?
Indeed,
I thought you already had the transfer function coefficients. If you don't have them yet, then indeed you will first have to interpolate your curve.
Best regards
01-21-2016 11:16 AM
Okay.
Thus I do not have to use tf2ams (using VBA, for ex.). Having interpolated that TF I'll put all coefficient to appropriate amesim's submodel. I guess its name is dynamic transfer function. There on the icon are two polinoms.
Do you know how to interpolate that curve (on pic.)? Is there such a function?
01-22-2016 05:11 AM - edited 01-22-2016 07:15 AM
Hi vitalii,
I think you have to look at "system identification" methods.
There is such a toolbox in Matlab. If you have access to it, it may help you to go from your transfer function to its linear representation.
I hope this helps.
01-27-2016 12:18 PM
I have spent days trying to solve this problem. I found what that function on a pic is a response function (Ampl/frequency with a lot of poles) not a transfer function, and it is impossible by using interpolation replace the linear system with it.
In this case I have to use 2nd order lag, maybe a few, and manualy look other they coefficients, trying to fit their summ responce to one what I need.
I am I right?