Mohammed Bouheraoua

Slip Recovery and Prevention in Pseudo Direct Drive Permanent-Magnet Machines

A Pseudo Direct Drive (PDD) is a permanent magnet machine with an integrated magnetic gear. It has two magnetically coupled rotors. When subjected to a load torque higher than the pull-out torque, slip between the two rotors may occur. Although this may not cause any damage to the PDD or the load, it could, if left uncontrolled, result in undesirable consequences such as loss of power transfer, excessive speed on the high-speed rotor (HSR), incorrect commutation signal, and/or loss of load speed/position control. This paper proposes a technique for a PDD equipped with a position/speed sensor on each rotor to control the slip caused by external overload torques and to enable a swift recovery when they are removed. However, when the PDD is equipped with only one sensor on the HSR, it is impossible to determine the position/speed of the low-speed rotor using an observer after slip occurs, which precludes a swift and controlled recovery. Therefore, a novel technique which prevents the slip between the two rotors under overload conditions is also proposed. Both techniques have been successfully implemented and demonstrated on a prototype PDD drive.

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.

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 (LSR). Due to the magnetic coupling between the two rotors, the PDD machine exhibits low stiffness and non-linear torque transmission characteristics, and hence, the position of the high-speed rotor (HSR) cannot be determined using simple gearing 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.

Slip recovery and prevention in Pseudo Direct Drive permanent magnet machines

A Pseudo Direct Drive (PDD) is a permanent magnet machine with an integrated magnetic gear. It has two magnetically coupled rotors. When subjected to a load torque higher than the pull-out torque slip between the two rotors may occur. Although, this may not cause any damage to the PDD or the load, it could, if left uncontrolled, result in undesirable consequences such as loss of power transfer, excessive speed on the high-speed rotor, incorrect commutation signal and/or loss of load speed/position control. This paper proposes a technique to control slip caused by external overload torques and enable a swift recovery when these are removed for a PDD equipped with a position/speed sensor on each rotor. However, when the PDD is equipped with only one sensor on the high-speed rotor, it is impossible to determine the position/speed of the low-speed rotor using an observer after slip occurs, which precludes a swift and controlled recovery. Therefore, a novel technique which prevents the slip between the two rotors under overload conditions is also proposed. Both techniques have been successfully implemented and demonstrated on a prototype PDD drive.

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.

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.