Magnet demagnetization observation or permanent magnet synchronous motor

Accurate information of rotor permanent magnet field is needed in permanent magnet synchronous motor(PMSM) control, but this information is variable under demagnetization conditions, such as high temperature or peak current. Nonsinusoidal flux density distribution caused by demagnetization induces to torque ripple, which degrades the PMSM drive performance. To estimate flux magnitude, a Kalman filter is built by using stator current and PM flux as state variables. The estimation method can accurately track the diversity of permanent flux and is robust to motors’ parameters. The flux linkage is represented by means of Fourier series expansion, and the observe method is used for the online detection demagnetization of PMSM. Experimental evaluations of flux linkage are carried out on a DSP-controlled PMSM drive platform. Test results obtained demonstrate the effect of the proposed method.