- #1
CremeBrulee
- 8
- 0
My books aren't clear at running through these inverse laplace transforms and this ones got me snookered. I'm trying to perform the laplace transform of:
1/s + 40/(24s^2 + 40s + 40)
Factor out 24 becomes
1/s + 1.667/(s^2 +1.667s +1.667)
Finding A, B, C
A/s + Bs+C/(s^2 +1.667s +1.667)
A=1
B=-1
C=-1.667
Substituting back into Eq becomes
1/s - (s+1.667)/(s^2 +1.667s +1.667)
However, I'm stuck here as the Eq doesn't look like its in the correct form to use in the inverse laplace tables? Do I need to manipulate denominator to present as (s+...)(s+...) using roots? Roots are found to be -0.833 +/- j0.986
Or split numerator into two parts ie 1/s - (s+1)/(s^2 +1.667s +1.667) + 1.667/(s^2 +1.667s +1.667)
Or both??
1/s - (s+1)/(s+(-0.833)) + j0.986) + 1.667/(s+(-0.833)) - j0.986)
Using the transform table at:
http://www.swarthmore.edu/NatSci/ec...nMethods/LaplaceZTable/LaplaceZFuncTable.html
Item 16 in the table looks like similar format but I believe Item 18 is closer after finding wn=1.29 & zeta=0.646 however, using item 18 doesn't account for the additional s in the numerator??
I feel I'm close but not quite there to finding this solution and its frustrating me! Any help or direction would be much appriciated.
1/s + 40/(24s^2 + 40s + 40)
Factor out 24 becomes
1/s + 1.667/(s^2 +1.667s +1.667)
Finding A, B, C
A/s + Bs+C/(s^2 +1.667s +1.667)
A=1
B=-1
C=-1.667
Substituting back into Eq becomes
1/s - (s+1.667)/(s^2 +1.667s +1.667)
However, I'm stuck here as the Eq doesn't look like its in the correct form to use in the inverse laplace tables? Do I need to manipulate denominator to present as (s+...)(s+...) using roots? Roots are found to be -0.833 +/- j0.986
Or split numerator into two parts ie 1/s - (s+1)/(s^2 +1.667s +1.667) + 1.667/(s^2 +1.667s +1.667)
Or both??
1/s - (s+1)/(s+(-0.833)) + j0.986) + 1.667/(s+(-0.833)) - j0.986)
Using the transform table at:
http://www.swarthmore.edu/NatSci/ec...nMethods/LaplaceZTable/LaplaceZFuncTable.html
Item 16 in the table looks like similar format but I believe Item 18 is closer after finding wn=1.29 & zeta=0.646 however, using item 18 doesn't account for the additional s in the numerator??
I feel I'm close but not quite there to finding this solution and its frustrating me! Any help or direction would be much appriciated.