A family of linear, continuous-time plants parametrized by a vector of
unknown parameters taking values in a known finite set is considered.
The problem investigated consists in finding a linear discrete-time c
ompensator that, independently of the actual value of the parameter ve
ctor, guarantees zero continuous-time steady-state output error, with
respect to a given continuous-time external reference. It is shown tha
t the problem admits a solution in the class of periodic controllers.