Extended high gain observer design for a class of MIMO non-uniformly observable systems

This paper deals with the design of an Extended High Gain Observer (EHGO) for a large class of Multiple Input Multiple Output (MIMO) non-uniformly observable systems. Indeed, the involved system nonlinearities does not assume the usual triangular structure as it is often the case when a high gain approach is adopted. This structure constraint relaxation is achieved by an appropriate use of the characteristic indices associated to the state components. There are two fundamental features that are worth to be pointed out. Firstly, the gain of the proposed EHGO is provided by an appropriate Riccati Ordinary Differential Equation (ODE). Secondly, the convergence of the observation error is guaranteed under some persistent excitation condition which can be checked on-line. Simulation results are given to illustrate the performance of the proposed EHGO.