Open-Loop Self-Calibration of Position Sensor Offset in SM-PMSM Drive Systems

Abstract

Field-oriented control (FOC) or vector control is a formidable control strategy for permanent magnet synchronous machines (PMSMs) due to high dynamic torque response. However, FOC requires rotor flux orientation information, typically obtained using a position sensor mounted on the motor. The relative displacement between the position sensor and the rotor zero location is a key calibration required to properly orient the stator field based on the rotor magnetic field. A method is proposed herewith that enables the calibration of this relative offset between the position sensor and the rotor zero that reduces the overall manufacturing floor space and manufacturing time. The proposed scheme exploits hardware and software components that are readily available on the motor-drive system for FOC control. The self-calibration scheme generates a slowly rotating stator flux vector to rotate the motor rotor under the no-load condition to collect information about the position sensor alignment. Lack of a need for specialized measurement in comparison to conventional methods saves and space while reducing the calibration time. The novelty lies in the ability to self-calibrate and, in doing so, reduces resource utilization. Analysis, simulation, and experimental results are provided to validate the proposed methodology.