Mahsa Rafiee - Electrical Engineering Department- Shahid Bahonar University of Kerman
Mojtaba Barkhordari Yazdi - Electrical Engineering Department- Shahid Bahonar University of Kerman

A hybrid observer for systems with hard nonlinearity is proposed in this paper. Most observers proposed for nonlinear systems in literature are designed based on approximate linearization. Extended Kalman filter (EKF) and Unscented Kalman filter (UKF) are two common Kalman-based observers have been proposed for nonlinear systems. However, in the presence of so-called hard nonlinearity such as saturation or dead zone, common nonlinear observers’ performance is degraded. The structure of the proposed hybrid observer consists of discrete observer and continuous observer on interaction. The discrete observer reconstructs active mode of the system and the continuous part estimates the continuous states. It is shown that the designed hybrid observer is stable and the estimation error is small according to dwell time theory. Finally, simulation results are presented for a DC motor with input saturation. Comparing the results presented for hybrid observer, EKF and UKF illustrates the effectiveness of the proposed method

Nonlinear system, hybrid observer, hard nonlinearity, input saturation, observer, hybrid system, Kalman filter