Reduced-order Observer Design for One-sided Lipschitz Nonlinear Systems with Unknown Inputs

This paper considers the reduced-order observer design problem for one-sided Lipschitz nonlinear systems with unknown inputs. The systems under consideration are a larger class of nonlinear systems than the well-studied Lipschitz systems and have inherent advantages with respect to conservativeness. For such systems, we propose a reduced-order unknown input observer (UIO) by using the linear matrix inequality (LMI) technique. Sufficient conditions that guarantee the existence of the reduced-order UIO are established and transformed into the format of LMIs via using the matrix generalized inverse technique. Simulation results are finally given to illustrate the effectiveness of the proposed design.