Why do I get the error "Too many input arguments"?

I am attempting to run a nonlinear grey box estimation, but when I run code to estimate unknown parameters, it says I have too many input arguments. I made sure to match the dimensions of the iddata object and the idnlgrey object, so I don't know where my problem lies.

The error is:

>> DOF2grey

Error using iddata/nlgreyest (line 59)

Error or mismatch in the specified ODE file "DOF2greyfxn".

The error message is: "Too many input arguments."

Error in DOF2grey (line 20)

nlgr = nlgreyest(estdata, nlgr, opt); %estimates unknown parameters in(nlgr)

my code is shown below:

filename = 'DOF2greyfxn'; %calls model file
Order = [4 2 4]; %number of outputs, inputs, states
    %check book to see if 4 inputs are necessary in state eqs

global u0 omega m1 m2 k1 k2 c1 c2

Parameters = {u0,omega,m1,m2,k1,k2,c1,c2};
InitialStates = [0; 0; 0; 0]; % x1 position, x1 velo, x2 pos, x2 velo
Ts = 0; %sample time = continuous time


nlgr = idnlgrey(filename, Order, Parameters, InitialStates, Ts, 'Name','DOF2grey'); %setup nlgrey object 

setpar(nlgr,'Fixed',{true true true true true true false false}); %tells matlab which parameters to estimate (c1, c2)
nlgr = setinit(nlgr, 'Fixed', {false false false false}); % tells matlab to estimate the initial states (all of them)

estdata = iddata(x, u, 10/1417153); %creates data object based on ode45_2DOF, input (u), output (x), sample time = data points/total time

opt = nlgreyestOptions('Display', 'on'); %shows estimation progress
nlgr = nlgreyest(estdata, nlgr, opt); %estimates unknown parameters in(nlgr) 
    %using estdata as input argument, estdata and nlgr must have same input and output dimensions

present(nlgr)
size(estdata)


compare(estdata,nlgr)

it uses this function to model the nlgrey object:

%6-20-19

function [dx, y] = DOF2greyfxn(t, x, u, u0, omega, m1, m2, k1, k2, c1, c2)


y = [x(1);x(2);x(3);x(4)];
dx = [x(2);(((-k1 - k2)/m1)*x(1) + ((-c1 - c2)/m1)*x(2) + (k2/m1)*x(3) + (c2/m1)*x(4) +(k1/m1)*u(1) + (c1/m1)*u(2))
    ;x(4); ((k2/m2)*x(1) + (c2/m2)*x(2) + (-k2/m2)*x(3) + (-c2/m2)*x(4))];
end

and it uses this data from this function and a corresponding ode45 file to create the iddata object:

function [dx, y] = DOF2damped(t, x)
u0 = .1; %amplitude ()
omega = 1; %hz
m1 = 0.85048569375; %kg
m2 = 0.7370876; %kg
k1 = 100000; % N/m 35
k2 = 356.9085; % N/m
c1 = 100000; %N/m*s
c2 = 1; %N/m*s
u = [u0*sin(omega*t); u0*omega*cos(omega*t)];
y = [x(1);x(2);x(3);x(4)]; %x1, x1dot, x2, x2dot
dx = [x(2);(((-k1 - k2)/m1)*x(1) + ((-c1 - c2)/m1)*x(2) + (k2/m1)*x(3) + (c2/m1)*x(4) +(k1/m1)*u(1) + (c1/m1)*u(2))
    ;x(4); ((k2/m2)*x(1) + (c2/m2)*x(2) + (-k2/m2)*x(3) + (-c2/m2)*x(4))];
end

%if variables are defined as global inside function, takes forever to run

ode file:

clear 
close all
clc

global u0 omega m1 m2 k1 k2 c1 c2

tspan = [0 10];


x0 = [0;0;0;0];
[t, x] = ode45(@(t,x)DOF2damped(t, x), tspan, x0); 
u = [(u0*sin(omega*t)), (u0*omega*cos(omega*t))];

plot(t, x, t, u)

Thanks for any help

[KALYAN ACHARJYA]

Not sure, I have doubt with nlgreyest options, try with default options.

[Ben25]

I get the same error with default options

Answer 1

[Valerie Cala]

unction [dx, y] = DOF2greyfxn(t, x, u, u0, omega, m1, m2, k1, k2, c1, c2,varargin)

y = [x(1);x(2);x(3);x(4)];

dx = [x(2);(((-k1 - k2)/m1)*x(1) + ((-c1 - c2)/m1)*x(2) + (k2/m1)*x(3) + (c2/m1)*x(4) +(k1/m1)*u(1) + (c1/m1)*u(2))

;x(4); ((k2/m2)*x(1) + (c2/m2)*x(2) + (-k2/m2)*x(3) + (-c2/m2)*x(4))];

end

Try this and run the code again.