On the Enhancement of High-Gain Observers for State Estimation of Nonlinear Systems

An enhanced high-gain observer is proposed to estimate the state variables of dynamic systems with Lipschitz nonlinearities. Such an observer has a more general structure as compared with the standard high-gain observer, which can be regarded as a particular case of enhanced high-gain observer because of a special choice of the design parameters. The more general structure allows for additional degrees of freedom in the selection of the observer parameters, which however entails some difficulties in the design. To overcome such difficulties, a convenient design procedure is presented that is based on the use of the Young inequality and linear matrix inequalities. Numerical results are reported to evaluate the effectiveness of the proposed observer and its related design tools as compared with the high-gain observer.