A Novel Inertia Identification Method and Its Application in PI Controllers of PMSM Drives

A novel method for inertia determination of a permanent magnet synchronous machine (PMSM) drive is proposed and analyzed, which employs a sinusoidal perturbation torque with a dc offset to drive the PMSM, and the amplitudes of reference sinusoidal torque and sinusoidal speed response are used to compute the system inertia. Compared with other methods, it is robust and fast to obtain the accurate quantity of the inertia. First, the inverter measures the resistances and inductances of a PMSM through a static voltage vector and stand-still frequency response experiments. The parameters are adopted to design the current proportion and integral controller and make both dq-axes currents to perform the first-order response. Second, the results of constant torque experiment employing the current controller are applied to get the friction coefficient and no-load torque. Third, a sinusoidal torque with a dc offset is applied and the response performs a sinusoidal speed with a constant offset. All the above experimental results and other preinstalled parameters are employed to get the system inertia, and the accuracy is verified by another experiment. As compensation for a position signal from a hall sensor, a corresponding method is also proposed to compute the sinusoidal speed response amplitude, which is the key in the procedure.