Global nonlinear observers

This paper discusses the construction of global observers for nonlinear discrete time systems. The observers do not rely on local linearization(s). The observers apply the Newton-Raphson numerical equation solving procedure to a nonlinear function constructed from the original output function. Based on this approach, several candidate state estimators are constructed, each candidate is assigned a confidence level based on how well it predicts the current measured output, and the state estimator is chosen to be the candidate with the highest confidence level. The use of confidence levels is discussed as an application of fuzzy logic. An example is presented.