Newton observer design in the absence of an exact discrete-time model

We study the Newton observer design, developed by P. E. Moraal and J. W. Grizzle (1995), when the exact discrete-time model is not known analytically. We eliminate the dependence on this exact model by introducing continuous-time filters that produce the numerical value of the exact model. We then implement the Newton method with finite-difference and secant approximations for the Jacobian. The proposed method offers flexibility to be implemented with nonuniform, or event-driven sampling.