Vector error

Hi,

I keep getting an error when I change a parameter at a certain time in my simulation of an aircraft braking. I am using an s-block which performs my integration and outputs the velocity and displacment of the aircraft as a real vector with two outputs.

However when I change the friction co-eff. ur from 0.026 to 0.528 i get this error:

State derivatives returned by S-function 'spoilers' in 'scott/Deceleration' during flag=1 call must be a real vector of length 2.

My program is as follows:

%Rolling friction (to change when brakes are applied) ur=0.026; if t>0.3 ur=0.528; end

%Drag co-efficient (possibly read from table) cd=0.0641; cl=0.749; if t>0.7 cd=0.0978; cl=0.536; end

%GI selected, one engine in operation: a=85; b=7.241; c=1.367; d=0.0078;

%Aerodynamic and friction loading e=(0.5*p*S*(cd-(cl*ur))); f=-(ur*W);

% Equations to be integrated xdot (1)=((a+f)+(b*x(1))+((-c-e)*(x(1)^2))+(d*(x(1)^3)))/m; xdot (2)=x(1);

% Perform integration. vdot=xdot (1); sdot=xdot (2);

sys = [vdot; sdot;];

Does changing from 0.026 to 0.528 drastically affect the equation xdot (1) to the point where it cannot return a real vector?

Any help is welcome.

[Jan]

Please format the code to increase the readability.

Answer 1

[Jan]

Is "sys" the output of you function? Then simply display the values of "sys" before the function is left to find out, why Matlab thinks, it is not a vector of 2 real elements.

Answer 2

[Gustavo Mattos]

It happened to me when I was dealing with an unstable system (sys -> Inf).