State Observer with Relaxed Excitation Conditions with Application to MagLev System

This paper presents a modified state observer for a nonlinear system. Recently presented parameter estimation-based observer for such system uses Dynamic Regressor Extension and Mixing (DREM) procedure and requires non-square integrability property for the regressor to guarantee that an observer error convergences to zero. However, it is not satisfied in some operating modes. For example, when the object is stabilized in a constant position. As an application a model of one degree of freedom magnetic levitation system is considered. Only the electromagnet coil current and voltage are measured, and the flux, speed and position values are reconstructed with observers. The proposed finite time modification for the flux observer requires the weaker interval excitation condition, which is fulfilled during the transient process. The simulation results demonstrate the efficiency of the algorithm.