Exercise 
 Parametric zero uncertainty in zero form

Consider the following alternative form of parametric zero uncertainty Gps  s  zpG
s zmin
zp
zmax 

which caters for zeros crossing from the LHP to the RHP through the origin

corresponding to a sign change in the steadystate gain
Show that the resulting multiplicative weight is wI s  rz zs  z and explain why the set of plants given by 
 is entirely dierent from that with the zero uncertainty in time constant

form in 

Explain what the implications are for control if rz