Enhancing Sensorless Start-Up in PMSM: Analysis and Optimization of Open-Loop Technique for Smooth Transitions

Permanent Magnet Synchronous Motors (PMSMs) are widely used in various applications because of their high efficiency, torque-to-weight ratio. Sensorless control algorithms, particularly those that eliminate position or speed sensors, have become essential for reliable and cost-effective motor drives. The sensorless algorithms are mainly based on back-emf. Since sensorless back-emf estimators are inaccurate in low angular velocity, initiating motor movement from standstill remains a challenge. A current-frequency (I-f) Open-Loop Start-Up Technique designed to start the motor but can cause current, torque disturbances during startup. This paper aims to analyze this I-f method, minimize current ripple (torque and audible noise), and ensure seamless transitions through five distinct start-up stages, ultimately leading to closed-loop operation. The proposed improvements use a model-based approach implemented with Scilab and XCOS for simulation and HW in the loop testing.