A Two-Stage Pre-Positioning Method for Resolver Zero-Offset Calibration in PMSM

Abstract

High-performance control of Permanent Magnet Synchronous Motors (PMSMs) heavily relies on accurate rotor position information. However, the inherent zero-offset error in resolvers can lead to controller output disturbances and even induce significant safety hazards such as system shutdown. Therefore, this paper designs and implements a detection strategy for the zero-offset angle suitable for zero and low-speed operating conditions. To overcome the dead-zone issue in single pre-positioning at a power angle of π-where zero electromagnetic torque prevents rotor movement-a "two-stage pre-positioning" correction method is proposed. This approach implements an open-loop angle injection strategy. First, a 0° virtual angle and quadrature-axis current are injected for initial positioning. Then, the virtual angle steps to 90°, triggering a second positioning. This instantaneous 90° commutation of the stator field generates maximum transient torque, overcoming static friction and load torque to precisely align the rotor. Experiments validate that the proposed two-stage pre-positioning method safely and rapidly aligns the rotor to a determined position, enabling the acquisition of the actual zero-offset angle.