Rotor Position Estimation of a Pseudo Direct-Drive PM Machine Using Extended Kalman Filter

The paper describes an improved method to control a pseudo direct-drive (PDD) permanent magnet machine with only one sensor on the low-speed rotor. Due to the magnetic coupling between the two rotors, the PDD machine exhibits low stiffness and nonlinear torque transmission characteristics, and hence, the position of the high-speed rotor (HSR) cannot be determined using a simple gear ratio relationship. An extended Kalman filter is proposed to accurately estimate the position of the HSR which is used to provide electronic commutation for the drive. The technique has been implemented on a prototype PDD subjected to various speed and load torque profiles.