This paper presents a new technique for nonlinear continuous-time observer design based on the differential state-dependent Riccati equation (SDRE) filter, with guaranteed exponential stability. Although impressive results have rapidly emerged from the use of SDRE designs for observers and filters, the underlying theory is yet scant and there remain many unanswered questions such as stability and convergence. In this paper, Lyapunov stability analysis is used to obtain the required conditions for exponential stability of the estimation error dynamics. Furthermore, through a simulation study of a second order nonlinear model, which satisfies the stability conditions, the promising performance of the proposed observer is demonstrated. Finally, in order to examine the effectiveness of the proposed method, it is applied to highly nonlinear flux and angular velocity estimation problem for induction machines. The simulation results verify how effectively the modification proposed in this paper can increase the region of attraction and the observer error decay rate.

Keywords: SDRE technique, SDC representation, nonlinear observer, stability analysis, Lipschits conditions, PM synchronous motor

Full-Text [PDF 409 kb]   (4536 Downloads)