Functional observer design for a class of multi-input and multi-output nonlinear systems

A functional observer design method is presented for a class of multi-input and multi-output nonlinear systems. The existence conditions of a functional observer are obtained by a rank condition and solving a linear matrix inequality. The proposed functional observer can estimate the system state and unknown input simultaneously. Moreover, exact asymptotic convergence of the estimate can be achieved. Through an example, it will be illustrated that the proposed approach can provide a smaller order of observer than that of the conventional approaches, while maintaining satisfactory performances.