A New Rotor Position Estimation Method for Spherical Reluctance Motor Based on Inductance Characteristics Obtained From Measurement

Since the spherical reluctance motor (SPRM) works in saturation, it is difficult to estimate the rotor position. In this article, a new rotor position estimation method for SPRM is proposed. In order to accurately estimate the rotor position, according to the inherent characteristics between phase inductance, rotor angle, and phase current, the phase inductance–rotor angle curve is divided into three segments. The idea of scaling is adopted to deal with the analytical expression of each segment, and the three analytical expressions corresponding to the three segments are generated through linear function and quadratic function. The coefficients of each analytical expression are determined through a small amount of the measured inductance data. Experiment and comparison results show that the proposed method can effectively and accurately estimate the rotor position.

I. Introduction

Spherical motor is a new type of motor proposed in the past three decades, and a spherical motor has the ability to carry out multi-degree-of-freedom (multi-DOF) motion [1], [2]. With the continuous development of machining technology and computer-aided software, many different types of spherical motors have been designed, processed, and analyzed [3], [4]. According to the needed materials, the existing spherical motors are mainly divided into permanent magnet spherical motor (PMSM) [5], [6] and spherical reluctance motor (SPRM). SPRM is a new type of spherical motor with simple structure and small size, which has a wide application prospect in the field of industrial production. Accurate rotor position information is the premise for spherical motors application in various fields [7]. For example, in industrial processing, accurate rotor position information is the key to manufacture accuracy.