Digital Steady-State Error for a Ramp input

[sspj9]

Since the stead-state error is given by:



Hence X(z) = G(z)*U(z) where U(z) = (0.2z^-1)/(1-z^-1)^2 Which is the ramp input in Z-domain at Ts=0.2.

This would simplify to xss = lim(z->1)[(z^-1)/(1-z^-1)G(s)] However substituting z=1 in denominator would yield infinity...

This is definitely not the case as in my simulation there is a slight steady state error.

What am I missing here please?