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This paper presents an observer-based position sensorless control method with signal injection. An extended electromotive force (EEMF) observer is suitable for salientpole synchronous motors, because position information of EMF and saliency are both included. Signal injection is needed to make use of the position information of saliency at low speed. However, observer consists of a low-pass filter. Therefore, position information of saliency has not been used enough for the EEMF observer.In this paper, signal injection method without torque ripple is applied to make effective use of the EEMF observer at low speed. The signal frequency can be selected in a bandwidth of the observer. Then, position estimation method based on heterodyne detection with the filter of the EEMF observer is proposed. The proposed technique makes it possible to expand the operating range of the EEMF observer to lower speed. The validity of the proposed control is confirmed by experiments.

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So far a lot of sensorless control methods have been proposed for permanent-magnet synchronous motors (PMSM).However, application which require the response at transition is limited in current methods, and the expansion of coverage of sensorless control is requested. In this paper, an extended flux is defined and minimal order observer estimating it is proposed. Then, the poles of the minimal order observer are assigned, considering robustness to velocity estimation error and suppression of higher harmonic components. Assigning poles like this, this observer becomes robuster to velocity estimation error at transition than conventional method. By this characteristic, the improvement of the response can be expected. The performance of proposed method is shown by experiments.

This paper deals with an amplitude-adjusting method for signal injection in position sensorless control of interior permanent magnet synchronous motor (IPMSM) drives. Signal injection is necessary for position estimation at standstill and low speeds. Response signals to the injected signals have position information because of the saliency of the IPMSMs. The position information appears in inductances depending on the rotor positions; therefore, time derivative of motor currents has to be measured directly or indirectly. The position estimation method discussed in this paper is based on an extended electromotive force (EEMF) model. Although the EEMF model is mainly used in middleand high-speed regions of IPMSM drives, it can be applied to all speed regions by combining it with signal injection methods. We adopt a signal injection method to stabilize the estimation and reduce the effects of disturbances. Then, the amplitude of the signal currents is adjusted to maintain a sufficiently high amplitude of EEMF against disturbances. Signal setting becomes easier because the lower limit of EEMF can be adjusted against the degree of disturbances.