Load Torque and Moment of Inertia Identification for Permanent Magnet Synchronous Motor Drives Based on Sliding Mode Observer

In this paper, a load torque observer and two moment of inertia identification methods are developed for permanent magnet synchronous motor drive systems. First, the load torque identification method is proposed based on sliding mode observer, in which the mismatches of moment of inertia, electromagnetic torque, and viscous friction are all considered. It is analyzed that the chattering phenomenon will be well weakened if appropriate observer parameters are chosen. Second, based on the property that the mismatch of the moment of inertia will cause the load torque observation error, two types of moment of inertia identification methods, called direct calculation (DC) method and proportional integral (PI) regulator method, are presented to identify the moment of inertia. In addition, the identification errors of the DC and PI regulator methods are also analyzed theoretically. Simulation and experimental results show that compared with the conventional identification method of the moment of inertia, the proposed DC and PI methods have improved estimation accuracy. Moreover, the presented load torque observer also has high observation precision and fast convergence speed.