Transfer function from ARX-model

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Viktor
Viktor 2013-4-11
编辑: John Kelly 2015-2-26
Im trying to get a transfer function from an arx model. I have tried to follow an MATLAB-example that i found on the homepage. I think my ARX model is pretty good but i dont really know how to get a good op-point for the linearization
Im using the example file twotankdata with 1 input and 1 output.
Help would be greatly appreciated!
This is how far im currently at:
load twotankdata.mat
ze = iddata(y, u, 0.2);
m3 = nlarx(ze,[2 2 3],wavenet('num',8));% na=nb=2 and nk=3
figure(2);step(m3,60)
stepinput = iddata([],[zeros(35,1);ones(1500,1)],m3.Ts);
%Dont know what happends here!
x0 = findop(m3,'steady',1,NaN);
sys2 = linearize(m3,1,x0)
figure(4);step(sys2,60)

回答(1 个)

Rajiv Singh
Rajiv Singh 2013-4-11
编辑:John Kelly 2015-2-26
  2 个评论
Viktor
Viktor 2013-4-11
Thank you for you answer.
Thats the example i have been following. I dont understand whats happening under point 4:
Compute the operating point corresponding to T = 20.
stepinput = iddata([],[zeros(10,1);ones(200,1)],...
nlsys.Ts);
% Compute operating point.
[x,u] = findop(nlsys,'snapshot',20,stepinput);
Arkadiy Turevskiy
Arkadiy Turevskiy 2013-4-11
As stated here:
[X,U] = findop(SYS,'snapshot',T,UIN,X0) computes the operating point at a simulation snapshot of time T using the specified input and initial state values

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