This paper addresses the asymptotic worst-case properties of set membe
rship identification (SMID) algorithms. We first present a set members
hip identification algorithm which can be used with a model structure
consisting of parametric and nonparametric uncertainty, as well as out
put additive disturbances. This algorithm is then studied in the conte
xt of asymptotic worst-case behavior. We derive lower bounds on the wo
rst-case achievable identification error measured by the volume, as we
ll as the sum-of-sidelengths of the identified ellipsoidal uncertainty
sets. We then show that there exist inputs which can shrink the uncer
tainty sets to these lower bounds.