Concept and Implementation of a Rotor Position Detection Method for Permanent Magnet Synchronous Machines Based on Linear Halls

The purpose of this paper is to propose and implement a novel rotor position detection method for permanent magnet synchronous machines (PMSMs) based on linear Halls, which are embedded inside of stator of PMSMs. A three-phase 9-slots/8-poles PMSM is exampled to verify the method. Firstly, a special point located in stator yoke (back-iron) is found by two-dimensional finite element analysis (2D-FEA), where the open-circuit flux-density due to permanent magnets versus rotor position (BPM) shows a high amplitude and good linearity, while the armature-reaction flux-density (Barmature) due to armature currents exhibits a low amplitude and good linearity versus armature currents. Then, an analytical model is built and the analytical relationship between armature currents and the Barmature is derived. Based on the analytical mode, BPM can be obtained by separating the Barmature from the synthetic magnetic field (BSynthetic). Thereafter, the resultant BPM can be used to detect the rotor position information with differential-type piecewise-linear analytical method. The feasibility of the proposed detection method is verified by co-simulations and experiments. The simulation results show that the novel linear Hall-based angle sensor can achieve the accuracy equivalent to 3000-line. The experimental results indicate that compared with an encoder, the maximum error of electric angle position at different speeds is less than 0.3%.