Robustness of Double-Adaptive Observers

Abstract

The usual process identification methods for parameter adjustment, along with dead zone, are effective in providing a robust adaptive observer of an unknown plant under uncertain input disturbance and output measurement noise. But it is difficult to decide the size of the dead zone due to the lack of knowledge concerning the disturbance. Furthermore, an error may remain in the dead zone despite the existence or nonexistence of the disturbance and the noise. In this paper, we propose a double-adaptive observer and discuss its robustness. Unlike previous work, this scheme does not introduce parameters that depend on the characteristics of the unknown disturbance. So, when the disturbance or the noise does not exist, the parameters converge over time. The stability of the system is discussed and computer simulation results are presented.