Sensorless control of IPMSM for last 10 years and next 5 years

This paper presents the developments of sensorless control of interior permanent magnet synchronous machine (IPMSM) for last 10 years, which could be divided into the past and the present for each 5 years. Several popular methods developed for last 10 years would be described and evaluated, and the limitations with the methods are discussed. In the past a concept extended EMF (EEMF) was introduced and it can model IPMSM as a non-salient motor, meaning that the representation of IPMSM in the estimated rotor reference frame would be much simpler and accurate. However, because it still relied on back EMF, standstill operation was impossible. And, the position control of IPMSM could not be achieved with EEMF concept. For sensorless drive, the high-frequency signal injection method exploiting inherent saliency of IPMSM has been continuously developed for last 10 years and applied to various industry fields, where torque control at standstill is essential. Its performance has been improved but there are still many problems to be solved. In the present, the square-wave signal injection at estimated d-axis has improved the control performance conspicuously. However, there are strong demands to improve the control performance of sensorless drive, yet. Based on the problems in the present, in this paper the possible developments of sensorless drive of IPMSM in next 5 years are enlightened as the future of sensorless control.