How to define a polynomial orders ARX model [na nb nk], for a MISO system

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fabian
fabian 2013-6-26
I have to define polynomials ARX model orders [na nb nc], for a set of four inputs and one output as the need to use the tool NNSYSID Toolbox, the data are as follows:
load datoshistoricos.txt;
datoshistoricos;
u1=datoshistoricos(:,1);
u2=datoshistoricos(:,2);
u3=datoshistoricos(:,3);
u4=datoshistoricos(:,4);
y1=datoshistoricos(:,5);
z8=iddata(y1,[u1 u2 u3 u4],1);
Data set with 1 output and 4 inputs. The number of data points is 587. The inputs are
587 4
the output
587 1
delayest using the command I get the following error
delayest(z8)
Error using delayest (line 87) The combination of delay limits will result in 2560000 delay-combinations, which is more than the allowed number of tests (10000). Either make the delay span more narrow or increase maximum allowable tests using the sixth input argument of the "delayest" command.

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回答（1 个）

Rajiv Singh
Rajiv Singh 2013-6-29
Look up the documentation of delayest on how to put some limits on the values to be tested. Delay can also be determined by a study of impulse responses. For ideas on model structure configuration and delay estimation, see:
http://www.mathworks.com/help/ident/examples/model-structure-selection-determining-model-order-and-input-delay.html

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