Position and Speed Sensorless Control for IPMSM Based on Estimation of Position Error

In most variable-speed drives of PMSM, some type of shaft sensor such as an optical encoder or resolver is connected to the rotor shaft. However, such sensor presents several disadvantages such as drive cost, machine size, reliability and noise immunity. Therefore, the sensorless control of PMSM is desired and various sensorless control strategies have been investigated. This paper presents a novel sensorless control strategy for an interior permanent magnet synchronous motor (IPMSM). A new model of IPMSM using an extended electromotive force (EMF) in the rotating reference frame is utilized in order to estimate both of position and speed. The extended EMF is estimated by the least-order observer, and the estimation position error is directly obtained. The proposed scheme corrects the estimated position and speed so that the estimation position error becomes to be zero. The proposed system is very simple and the design of the controller is easy. Several drive tests are carried out and the experimental results show the effectiveness of the proposed sensorless control system.