greybox linear model error

I get the following error: "The number of inputs and outputs of the model must match that of the data." However, I have ensured the number of outputs are definitely correct - where have I gone wrong?

NB: y= 100x3, u=100x1

load v1v2;

y=[x_store simSoC_TECM];
u=simCurr_TECM;
data = iddata(y,u,1,'Name','Battdata'); %y=O/P (V1,V2), u=I/P (Ibat), Ts=1.
data.OutputName = {'BattV1','BattV2','BattSoc'};
data.OutputUnit = {'V','V','%'};
data.Tstart = 0;
data.TimeUnit = 's';

%%load parameters 

load rcbranch
R1=RpTF1mean(5,3);
R2=RpTF2mean(5,3);
T1=TauTF1mean(5,3);
T2=TauTF2mean(5,3);
R0=RoTFmean(5,3);
C1=T1/R1;
C2=T2/R2;

%%construct greybox model            
param    = {T1;T2;C1;C2;Cnom;R0}

linm = idgrey('batteryeq_lin',param,'c'); 

function [A,B,C,D] = batteryeq_lin(T1,T2,C1,C2,Cnom,R0,Ts)

A=[-1/T1 0 0;0 -1/T2 0;0 0 0]; %(V1 V2 SOC)
B=[1/C1;1/C2;-1/Cnom];
C=[-1 -1 -1];
D=R0;

%%Specify known and unknown parameters.

for i=1:1:5
linm.Structure.Parameters(i).Free = false;
end
linm.Structure.Parameters(6).Free = true;
linm.Structure.Parameters(6).Minimum = 45e-3;
linm.Structure.Parameters(6).Maximum = 90e-3;

%%Estimate R0.
tic
linm = greyest(data,linm)
toc

Thank you

Answer 1

[Prashant Arora]

Hi Imisi, In your code below

function [A,B,C,D] = batteryeq_lin(T1,T2,C1,C2,Cnom,R0,Ts)
A=[-1/T1 0 0;0 -1/T2 0;0 0 0]; %(V1 V2 SOC)
B=[1/C1;1/C2;-1/Cnom];
C=[-1 -1 -1];
D=R0;

C is defined as a row vector, which implies that the state-space model has only 1 output, as opposed to 3 outputs created with iddata. This is causing a mismatch and results in an error. Essentially C*x + D returns a scalar according to the equations you have specified.

[Imisi Jo]

Ah of course! Thank you.