A robust globally convergent position observer for the permanent magnet synchronous motor

Position observers are essential components in the design of sensorless controllers for electric motors. Their design is complicated by the fact that the motor dynamics is highly nonlinear and contains some uncertain parameters. In this paper a new robust, nonlinear, globally convergent position observer for surface-mount permanent magnet synchronous motors is proposed. A key feature of the proposed observer is that it requires only knowledge of the stator resistance and inductance with the mechanical parameters and the magnetic flux constant being unknown. Thanks to a new reparameterization of the motor dynamics only two parameters are estimated with a regressor consisting of filtered voltage and current, which is persistently exciting in normal motor operation. Realistic simulations and experiments show that the proposed observer outperforms other existing designs from the point of view of robustness and convergence rate.