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Homework Help: Control system question

  1. Apr 9, 2012 #1
    1. The problem statement, all variables and given/known data
    I have the following matrix:
    A=[0 -1; 0 -1]

    and i need to calculate: exp(At) in several ways, 2 of them are using the reverse Laplace transform and using: I + Ʃ(A^kt^k)/k!

    i have tried to start the series but i am getting an expression that i can't say which series it is,
    and when i try with Laplace i get the one of the matrix expressions is a step function..

    i will apreaciate the help...

    thanks!
     
  2. jcsd
  3. Apr 9, 2012 #2
    What are you getting for
    [tex](sI-A)^{-1}[/tex]
     
  4. Apr 9, 2012 #3
    this is what i get. but i can't find the reverse transform...
     

    Attached Files:

  5. Apr 9, 2012 #4
    You are dividing by the wrong thing. Divide by
    [tex]s(s+1)[/tex]
    instead of
    [tex]s(s+1)-1[/tex]
     
  6. Apr 9, 2012 #5
    but
    [tex]s(s+1)-1[/tex]
    is the deteminante..
    in oreder to reverse 2*2 matrix i do this:
    [a b ; c d]^-1 = [d -b; -c a] * 1/det
    no?
     
  7. Apr 9, 2012 #6
    1*0 = 0
     
  8. Apr 9, 2012 #7
    daaaam! right, thanks!
     
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