A Generalized Nonlinear Extended State Observer for Multi-output Lipschitz Systems

This paper introduces a generalized nonlinear extended state observer with a rigorous convergence proof enabling its usage for multi-output Lipschitz nonlinear as well as linear systems. Unlike the conventional nonlinear extended state observer, the proposed observer does not require that the system under consideration be in triangular canonical form. In the case of single output systems in triangular canonical form, the proposed observer can be viewed as an alternative to the celebrated nonlinear extended state observer. This observer enjoys fast convergence as well as small overshoot/ oscillation due to its switching logic. The proposed observer is further modified for disturbance decoupling and disturbance estimation. Simulations are included to examine the efficacy of the proposed observer in comparison to existing ones.