Obtain the transfer function for the following differential equation (dx)/(dt)+3x=f(t)

Elise Kelley

Elise Kelley

Answered question

2022-10-15

Obtain the transfer function for the following differential equation and check whether the input free solution is stable or not,
d x d t + 3 x = f ( t )

Answer & Explanation

Davin Meyer

Davin Meyer

Beginner2022-10-16Added 13 answers

Just solve it in Laplace:
x ˙ + 3 x = f ( t )
Applying Laplace transform and derivative property { f ˙ ( t ) } = s F ( s ) f ( 0 ), considering initial condition f(0)=0 :
s X ( s ) + 3 X ( s ) = F ( s )
X ( s ) ( s + 3 ) = F ( s )
Y ( s ) = X ( s ) F ( s ) = 1 s + 3
Using the transform { 1 s + a } = e a t
y ( t ) = e 3 t
Finally, you can see that it's stable. In fact the only pole of the function ( s = 3) is negative. This is clear on the time axis too, because the transient response goes to zero as t goes to infinity.

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