Nonlinear Modeling of Electromagnetic Forces for the Planar-Switched Reluctance Motor

Abstract

Planar switched reluctance motors (PSRMs) have the merits of simple structure, low cost, low heat loss, high precision, ease of manufacture, and strong adaptability of harsh environment, which directly transform the mechanical energy to electromagnetic energy available to planar motions without mechanical transmissions. Therefore, PSRMs are an attractive candidate in high-precision two-dimensional positioning devices [1], [2]. For PSRMs, accurate modeling of electromagnetic forces is the theoretical foundation of the design and control. However, electromagnetic forces are highly nonlinear and hard to be accurately modeled due to the inherently complex magnetic characteristics of PSRMs. There are primarily three methods utilized to model electromagnetic forces of switched reluctance motors (SRMs) up to now, which are the equivalent magnetic circuit method, the Maxwell stress method, and the virtual work method [3]-[5]. Additionally, the neuron network is also employed to model electromagnetic forces for a SRM [6]. Nevertheless, the modeling of electromagnetic forces for SRMs cannot be directly applied to PSRMs owing to their unique structure of magnetic circuit. For linear switched reluctance motors (LSRMs) and PSRMs, electromagnetic forces including thrust force and normal force have been modeled under linear magnetic circuit [7], [8], but the modeling of electromagnetic forces has not been formulated so far with consideration of magnetic saturation. Furthermore, the finite-element method (FEM) is frequently used to establish electromagnetic force model for SRMs, LSRMs and PSRMs [9]-[11], whereas FEM takes a long calculating time. Based on aforementioned analysis, the nonlinear modeling of electromagnetic forces has not been built analytically for PSRMs. Hence, it is necessary to derive the nonlinear modeling of electromagnetic forces for deeper investigation of PSRMs.