Comparison of Nonlinear Observers for the Back Electromotive Force of the Main Exciter of the Brushless Synchronous Starter/Generator

Using the main exciter (ME) as a quasi-resolver to perform sensorless starting control of the brushless synchronous starter/generator (BSSG) is a novel and promising strategy. The back electromotive force (EMF) of ME is essential information for this approach, however, which observer is suitable to obtain the complex sawtooth back EMF stays an open question. In this paper, three advanced nonlinear observers, non-singular fast terminal sliding mode observer (NFTSMO), high gain disturbance observer (HGDO), and high order disturbance observer (HODO), are constructed, and their performance is evaluated by estimation results of the back EMF of ME. Both the simulation and experiment results show that HODO has the best performance.