Speed Control for a Pseudo Direct Drive Permanent-Magnet Machine With One Position Sensor on Low-Speed Rotor

This paper describes a novel approach to operate a pseudo direct drive (PDD) permanent-magnet machine with a single sensor on the low-speed rotor (LSR). Due to the magnetic coupling between its two rotors, the PDD machine exhibits torsional oscillation when conventional control techniques are employed. While full state feedback (SFBK) control can effectively suppress torsional oscillation, the need for a position sensor mounted on the high-speed rotor (HSR) for electronic commutation imposes great constraints on the PDD mechanical design. A novel technique has been developed in order to control the PDD machine using a single sensor mounted on the LSR, whereas the position and speed of the HSR required for electronic commutation and SFBK control are estimated with an observer. Both the SFBK controller and observer are optimally designed using the genetic algorithm against a defined set of criteria and constraints. The proposed control technique has been validated by experiments on a prototype PDD system.