Find maximum on steady state condition from a vector (hard)

Hi,

I'm doing vibration analysist with labview and runink my simulink model on matlab. I'm using the variable "x_optimisee" as an array vector that contains few hundred thousand values from a 0 times to something like 15000. I need the amplitude of my graphic after a certain time. Usually I use function max(abs()) but this time I can't use it because it will thake the maximum of the transiant part witch is higher than the steady stade maximum. I know that I'm approx. in steady state condition after the 15 000th value. But this isn't necessarily a maximum. So I would like to have the maximum from 15 000 up to lenght(x_optimisee) ideally.

My program is included into a for loop because I have to try my equation at different frequency. So here is what I've done yet but it isn't working, just to show you the main idea.

Thank to the master that will be able to solve this!

 warning on
j=1;
clc
for omega=100:1:160;
    %sim Labo2
    sim Lab2simulinkoptimise % Simulink
    Xqueue_j=max(abs(x_optimisee));
    omega_g_j(j)=omega;
    Tq_j(j)=Xqueue_j*keqa/(m*e*omega^2);
    j=j+1;
end
for i=1:200000
    x_optimisee(i)=0;
end

figure(100) plot(omega_g_j,Tq_j)

The x_optimisee(i)=0 was a try to use a maximum on the same vector but with 0 on all values of the transiant condition. But this isn't possible because the amplitude Xqueue_j is needed into the loop. What would be a great way to solve this? Thank you!

Answer 1

[dpb]

How about showing us a plot of a typical time trace?

My first inclination would be to do some heuristic searches to find the "steady-state" location in time, then process off that.

But, as for the query as stated, it's simple enough to find a maximum over a portion of the vector as "maximum from 15 000 up to length(x_optimisee)"

idx1=15000;   % say, the "magic number" of SS condition arrival
[maxX,imax]=max(x_optimisee(idx1:end));  % max in that portion to end

To locate where this is in the original vector, just add the initial offset to the found location (less 1 to account for base 1 indexing)

imax=idx+imax-1;