State estimation for dynamical system described by linear equation with   uncertainty
  In this paper we investigate a problem of state estimation for the dynamical system described by the linear operator equation with unknown parameters in Hilbert space. We present explicit expressions for linear minimax estimation and error provided that any pair of uncertain parameters belongs to the quadratic bounding set. As an application of the main result we present the solution of minimax estimation problem for the linear descriptor differential equation with constant matrices. 
Serhiy Zhuk