On-line mechanical unbalance estimation for permanent magnet synchronous machine drives

An on-line mechanical unbalance estimation for permanent magnet synchronous machine (PMSM) drives is presented. At high speeds, either rotor or mechanical load unbalance generates vibration that can cause mechanical failure such as a defect of a bearing or shaft. To prevent failure and minimise mechanical vibration, the amount of the rotating unbalance should be detected in real time. The information of the estimated unbalance can be utilised to manage an operation to achieve the durability of mechanical parts. The dynamic nature of a mechanical system with a PMSM with regard to unbalance is investigated. From this examination, the models of the stator current in time and frequency domains for PMSMs are presented to develop a robust real-time unbalance estimation scheme. Based on the modelling and analysis of a rotating mechanical system using a PMSM drive, a compact unbalance estimation algorithm is proposed. The algorithm is combined with an open-loop torque observer and an unbalance estimator using a filter. Experimental results show the validation of the developed model and the proposed on-line unbalance estimation scheme.