Analytical rotor position estimation for SRM based on scaling of reluctance characteristics from torque-balanced measurement

In this paper, a novel analytical method is proposed for rotor position estimation of switched reluctance machine (SRM). The nonlinear reluctance characteristic of the SRM is divided into two parts, namely air gap and iron core, and analyzed in detail from the aspect of magnetic field. According to the inherent features of the reluctance characteristic, it is analytically expressed based on scaling. Two segments are considered, which are expressed as a linear function and a quadratic function, respectively. Then, the analytical expressions of rotor position are derived for each segment. The effectiveness of the proposed analytical estimation method is evaluated with detailed simulations and experiments under different operating conditions. The proposed method is accurate and just requires the reluctance characteristic at four or even two rotor positions, which can be conveniently measured by the torque-balanced method.