5. Non-stationary linear models

Non-stationary models are important because, while retaining the intrinsic properties of linear models, they enable us to pilot a non-linear system by linearization around a desired trajectory. We will not go into detail on these two aspects described in [S 7 035] . In this section, we will simply show that the principle of linear function observer design methods can easily be extended to this much more general type of model.

Consider a non-stationary linear model of the form :