“…For extending the functionality of the Kalman filter to nonlinear dynamic structures, a modified variant of it, the EKF, has been developed [26,27]. For a discrete, nonlinear system x k+1 = f (x k , w k ) and its observation y k = g(x k , v k ) , linear approximation close to a reference point (x k ,ŵ k ,v k ) can be formulated [28] as in Eq. (1):…”