A Gain Design Method for a Linear Extended State Observers to Improve Robustness of Deadbeat Control

This article proposes an extended state observer to broaden the stability range of conventional deadbeat controller. The proposed observer is constructed through the model of permanent magnet synchronous machine (PMSM) which considers the parameters mismatch and unmodeled nonlinear elements. For the high bandwidth of current loop, the closed-loop stability is not ensured through the stability of observer. Therefore, the effect on the closed-loop performance which is caused by the observer is analyzed through the closed-loop transfer function and proved that the deadbeat performance can be kept when the parameters are precise. Furthermore, the system robustness performance is improved through adjusting the observer gain properly when parameters mismatch exists. To ensure the closed-loop stability, H_∞ norm of the transfer function is chosen as an index to determine the two gain factors of observer. The effectiveness of the proposed algorithm is verified by Simulation and experimental results.