I have an error but I dont know where it is referring to "Index exceeds the number of array elements"

This is my code for the intepreted MATLAB function on simulink

function [XDOT] = RCAM_model(X,U)

% ---------- State and control vectors ----------
x(1) = X(1);    %u
x(2) = X(2);    %alpha
x(3) = X(3);    %q
x(4) = X(4);    %theta
x(5) = X(5);    %mass
x(6) = X(6);    %vertical
x(7) = X(7);    %horizontal


u1 = U(1);    %eledefl      
u2 = U(2);    %thrustvec 
u3 = U(3);    %power


% ---------- Constants ----------
b = 10.2;
c = 1.74;
S = 17.1;
initial_mass = 1248.5;
Ix = 1421;
Iy = 4067.5;
Iz = 4786;
Ixz = 200;

g = 9.81;
rho = 1.225;
speedsound = 340;

% ---------- Control limits ----------
u1min = 0;
u1max = 25*pi/180;

u2min = 0;
u2max = 90*pi/180;

u3min = 1;
u3max = 4;

if(u1>u1max)
    u1 = u1max;
else if (u<u1min)
    u1 =u1min;
end 

if(u2>u2max)
    u2 = u2max;
else if (u<u2min)
    u2 =u2min;
    end
    
if(u3>u3max)
    u3 = u3max;
else if (u<u3min)
    u3 =u3min;
end 


% ---------- Aerodynamic force coefficients ----------
CL = 6.44*x(2) + 3.8*c*x(3)/(2*x(1)) + 0.355*u(1);        % Lift
L = 0.5*rho*speed^2 * CL;
CD = 0.03 + 0.05*CL^2;      % Drag
D = 0.5*rho*speed^2 * CD;

Cm = 0.05 - 0.683*x(2) - 9.96*c*x(3)/(2*x(1)) - 0.923*u(1);  % pitching moment 
m = 0.5*rho*speed^2*S*c*Cm;

% ---------- Engine force  ----------
thrust = u(3) * ( (7+speed/speedsound)*200/3 + x(6)*(2*speed/speedsound -11) )


% ---------- XDOT  ----------
XDOT = [(thrust * cos(x(2)+x(2)) - D)/ x(5) - g*sin(x(4)-x(2));
        q - (thrust*sin(x(2)+u(2)) + L) / x(5)* x(1)  + g/x(1)*cos(x(4) - x(2));
        m/Iy;
        x(3);
        -200/60/60/1000 * thrust;
        x(1)*sin(x(4)-x(2));
        x(1)*cos(x(4)-x(2))]
    

Below is my initilaizing constants script and to run the simulink simulation

% Initialize constatns for the rcam simulation

clear clc
close all

%% Define constants 

x0 = [63.292; 0.043891; 0; 0.043891; 1248.5; 0; 0];   % u, alpha, q, theta, mass, vertical, horizontal

u = [0.021692; 0; 1];   % eledefl, thrustvec, power 

TF = 60;

%% Run the model
sim('RCAMSimulation.slx')

I cant run the simulation and I got the error:

• Error using InitializeConstants (line 15)
• Error due to multiple causes.
• Caused by:
• Error using InitializeConstants (line 15)
• Index exceeds the number of array elements (4).
• Error using InitializeConstants (line 15)
• Error in 'RCAMSimulation/Interpreted MATLAB Function' while evaluating expression.

Thank you for your help!

[Walter Roberson]

CL = 6.44*x(2) + 3.8*c*x(3)/(2*x(1)) + 0.355*u(1);        % Lift

Could you point me to where lower-case u is coming from in that function? You have a parameter which is U (upper-case) but I do not see u (lower-case) assigned to or passed in?

[Rachel Ong]

Hello, so should I be using the upper cause U instead of the lower case u? I am a bit confused there as well. The U or u I am referring to are the variables in the system.

[Walter Roberson]

If you want u(1) to refer to u = [0.021692; 0; 1]; % eledefl, thrustvec, power then I suspect you might need to use a global memory store and a "global" statement in the MATLAB code. https://www.mathworks.com/help/simulink/ug/using-global-data-with-the-matlab-function-block.html

Alternately, I think you just might be able to use the workspace variable in the definition for the value of a Constant block, which you would then connect as an input to the MATLAB Function Block.

[Rachel Ong]

I see okay let me try it out. Thank you.