# Step input applied for different seconds

4 views (last 30 days)
Mustafa Furkan on 21 Dec 2022
Commented: Star Strider on 25 Dec 2022
I want to apply step input to the system as in the graphs above, where the second values are seen in the row and column. Entries will start at 1 second and end at 5 and 40 seconds respectively. I want to plot the vibration graph x(t), and the amplitude graph of these vibrations, but I couldn't find where to start.

Star Strider on 21 Dec 2022
Experiment with this approach —
N = 1500; % Desired Length Of Simulation
t = linspace(0, 50, N);
u = @(tlen,lz) [zeros(1,lz) 10*ones(1,size(t(t<=tlen),2)-lz) zeros(1,size(t(t>tlen),2))]; % 'tlen'=Length Of '10' Region, 'lz'=Length Of Leading Zero Vector
u5 = u(5,2);
u40 = u(40,2);
figure
subplot(2,1,1)
plot(t, u5, 'g', 'LineWidth',1.5)
grid
title('u(5,2)')
ylim([0 15])
subplot(2,1,2)
plot(t, u40, 'b', 'LineWidth',1.5)
grid
title('u(40,2)')
ylim([0 15])
Use ‘t’ and ‘u(tlen,lz)’ as inputs to lsim to get the system response. Change ‘u(tlen,lz)’ to get the result you want.
.
Mustafa Furkan on 25 Dec 2022
It worked now thank you. Unfortunately, as you said, I don't get a different result than before. I guess I'll have to include values like mass stiffness to get a result as expected.
Star Strider on 25 Dec 2022
As always, my pleasure!
I have no idea what results are expected. It would appear that you would be using a state space realisation. There are likely documentation examples that could help code your system.
If necessary, you can use stepinfo with the arguments of all the step calls to get that information from each of them.

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