Page 56 - Servo Motors and Industrial Control Theory -

48 2 Feedback Control Theory Continued

Using the final value theorem the error becomes

e = K d

It shows that although the derivative feedback introduces damping, it introduces
2
a following error in the system. For acceleration input of θ = t by referring to the
i
table of Laplace Transform,
1
θ =
i
s 3

Using the final value theorem, it can be shown that
e =∞

It means that the steady state error tends to infinity as time is increased