A novel Sliding Mode Observer with multilevel discontinuous control for position sensorless PMSM drives

In this paper, a novel Sliding Mode Observer (SMO) is presented for estimating the rotor position angle of PM synchronous motors (PMSM) to achieve position-sensorless vector control. A multilevel discontinuous control is designed and applied as a substitute of sign function applied in conventional models. Compared to other SMO observers, the proposed observer can effectively circumvent the chattering problem in its discrete implementation as well as preserving the well-known SMO features due to the discontinuous control, such as robust estimation performance and low sensitivity to variation of machine parameters. As a result, ripples superimposed on the estimated currents are comparatively small and so is the estimation error of rotor position. In addition, by applying the multilevel technique, it would not be challenging any more to design the low pass filter used for the extraction of equivalent control with little attenuation and phase delay. The proposed observer is implemented in a DSP-based digital controller of a PMSM drive system. The feasibility and effectiveness are verified through experimental testing.