“…More recently, it is worth noting that for FMs, the system uncertainties, nonlinearities, and disturbances are unavoidable in modeling of dynamic system [9,[16][17][18], so the robust observer design problems are not easy to derive. In order to preserve the observer action under system uncertainties as well as nonlinearities, various methods to design of robust state observers (estimation or filtering), such as algebraic, geometric, generalized inverse, and variable structure observer (VSO) techniques have been used to the observer design in [8,12,19,20]. In many practice applications, the design of robust nonlinear observers is close to the actual dynamic behavior of nonlinear systems with uncertainty disturbance rather than linear observers.…”