Performance achievable in sensorless control of electrical drives strictly depends on the adopted synchronous machine. The combination of cross-saturation and saliency, both dependent by the current load and the rotor position, makes always the position estimation afflicted by an estimation error. When the machine is highly saturated, the sensorless control can even diverge resulting in a useless drive. Thus, it is of primary importance to know in advance the convergence region of the sensorless drive, i.e., the operating points, where the motor can be successfully controlled without a position sensor. The aim of this article is to show how to compute the estimation error, the saliency, and the convergence region (hereafter called self-sensing capabilities) starting from the flux linkages maps or, more generally, from the incremental inductances. The dependence on the rotor position is also considered. Finite element simulations and experimental measurements validate the proposed model. The code used to compute the self-sensing capabilities is available as an open source package.

The article deals with a position sensorless control for synchronous motor drive with an ease tuning procedure and a reduced number of tunable parameters. The rotating high-frequency (HF) signals injection is implemented and the elliptical shape of the HF-induced current trace is fitted by means of the least square (LS) algorithm. The ellipse tilt is related to the rotor position and the latter is estimated by processing the fitted coefficients of the ellipse mathematical equation. The proposed LS algorithm processes the measured currents, without the need to filter them as occurs in conventional injection methods. Furthermore, no motor parameters are required to tune the proposed rotor position observer. The method was validated throughout several experimental tests performed on an interior permanent magnet synchronous motor.

The conventional methods for estimating the rotor position of permanent magnet synchronous machines, at low speed range and characterized by rotor saliency, rely on high frequency voltage injection in the stator windings. Ordinarily, the rotor position estimation is achieved through the demodulation of the high frequency current response. In this paper, an alternative method is presented for detecting rotor position from the rotating high frequency injection current response. The proposed ellipse fitting technique is not affected by signal processing delay effects and it requires the tuning of only one parameter, called forgetting factor, making the studied method suitable for industrial application thanks to its minimal setup effort. The inverse problem related to the ellipse fitting is solved implementing a QR recursive least squares algorithm. Efficient updating QR factorization has been adopted because of its features in terms of numerical stability and required limited computational effort. The proposed sensorless control scheme is validated by means of many experiments.

Signal injection sensor-less control for synchronous machines is known to be afflicted by an estimation error dependent on the load current. The estimation error is related to the cross-saturarion and the saliency of the adopted synchronous machine. A motor can be more or less suitable for signal injection sensorless control compared to other motors with different designs or sizes. A sensorless drive can even be afflicted by the control divergence when the machine is highly saturated, resulting in a useless drive. Moreover, even when the control converges, the actual current control trajectory is different from the given reference. In this paper, a measurement procedure of the convergence region, i.e. the operating points where the motor can be successfully controlled without a position sensor is presented and validated. In particular, two different synchronous motors are considered, a permanent magnet assisted synchronous reluctance motor (PMA-SynRM) and a synchronous reluctance motor (SynRM).

Sensorless control schemes are object of great interest in the synchronous motor drives field. They permit to avoid the use of position sensors in the system, allowing several benefits. In this paper a sensorless control scheme is proposed for low speed or standstill operation of a synchronous motor drive, characterized by a rotor anisotropy. The method is based on a high frequency voltage injection in the stator motor windings. High frequency current response to this injection is obtained from the measured currents thanks to a high pass filter. These filtered currents describe an ellipse trajectory, that is deeply analysed considering all its components. In particular, ellipse major semi-axis tilt is related to the rotor position. A recursive least squares estimator is proposed for the ellipse equation coefficients identification. After some manipulations, the rotor position is extrapolated from these information.

This paper presents an investigation on the self-sensing capability of a dual three-phase synchronous reluctance motor. Self-sensing capability refers to the ability of the motor to properly operate in a sensorless drive. The multiphase machine is decomposed into two different three-phase systems according to the multi-stator approach. Several supply scenarios are studied where the two three-phase windings are controlled at different operating points along a reference trajectory. The analysis is carried out both with FEA simulations and experimental tests. In the first part of the paper the rotor is locked to derive the observer trajectories and find the regions in which the motor can operate without position sensor. A comparison between simulated and experimental results is given. Finally, a sensorless control strategy that allows exploiting the motor self-sensing capability under position sensor fault is developed and validated through experimental tests.