STATE ESTIMATION OF DYNAMICAL-SYSTEMS WITH NONLINEARITIES BY USING PROPORTIONAL-INTEGRAL OBSERVER

In this paper the application of a PI observer technique to dynamical systems with nonlinearities is proposed. The PI observer has two feedb ack loops, a proportional loop and an integral loop of the estimation error. In this way the PI observer combines the structures of the prac tical orientated nonlinearity observer developed by the third author a nd the classical Luenberger observer. The structure and the estimation performance of the PI observer are discussed and analysed. The result s show that the PI observer can estimate the states not only of linear systems, but also, more significantly, of systems with any arbitrary external input which appear as unknown input, nonlinearity or unmodell ed dynamics. It is shown that the PI observer works with weak assumpti ons, which can be fulfilled by many classes of systems to be observed. Owing to the weak assumptions it can improve many observer-based tech nical solutions as diagnosis or control based on observers. In the pap er the conditions are given and proved. The design method is declared and carried out with illustrative examples of a linear system and of a nonlinear system of a link manipulator with flexible joints. The resu lts are good and they show the efficiency of the PI observer. In the c ase of nonlinear systems the advantages of 'robustness' and the model independency of the proposed observer scheme can be shown clearly.