Modeling and Control of 'Pseudo' Direct-Drive Brushless Permanent Magnet Machines

This paper addresses the issues associated with the modeling and control of a novel 'pseudo' direct-drive machine which is realised by mechanically and magnetically combining a magnetic gear and a permanent magnet brushless electrical machine for general applications that require torque or speed control. It has been shown that due to lack of damping in the system, torsional oscillation may occur between the high- and low-speed rotors if a conventional field oriented control strategy is employed to control the 'pseudo' direct-drive machine. This problem has been circumvented by using an observer based full-state feedback control. The design of a reduced-order observer and state feedback control based on linear quadratic optimization is described. It has been shown that proposed observer structure and control strategy is effective in suppressing the torsional oscillation due to the non-rigid magnetic coupling between the two rotors.