matlab question response question

I have a control system with a PID controller, and im trying to simulate a system response, i need to plot the values first in a graph and then add the transfer function?

this is what i have found and im doing:

dt = 0.1; t = 0:dt:50; u = zeros(1,numel(t)); u(t<=20) = 45; u(t> 20 & t<=40) = -45; u(t> 40) = 0;

obviously with the lsim command

Is there a better way ?

Thanks in advance

Answer 1

[Mischa Kim]

John, you just need to build the signal (no need for plotting), e.g.,

 dt = 0.1;                % adjust as necessary
 t  = 0:dt:50;
 u  = zeros(1,numel(t));
 u(t<=20)         =  45;  % you probably want to use rad instead of deg
 u(t> 20 & t<=40) = -45;
 u(t> 40)         =   0;

and feed it as an input to the system.

[Mischa Kim]

Correct,

 lsim(sys,u,t)

or similar. You might have/want to specify initial conditions x0 for the system, in which case you'll have an additional parameter.