Simultaneous Identification of Load Torque and Moment of Inertia of PMSM Based on Variable Structure Extended Sliding Mode Observer

In this article, a variable structure sliding mode observer (VS-SMO) for load torque observation is designed by adding a decoupling term to the structure of the traditional sliding mode observer. The VS-SMO can remove the coupling relationship between the parameter to be estimated and the derivative of the estimated speed error, as well as the chattering signal in the estimated load torque. Then, a variable structure extended sliding mode observer (VS-ESMO) is designed on this basis, with the moment of inertia used as an extension, to achieve simultaneous identification of the load torque and the moment of inertia. This article analyzes the estimation errors and the impact of measurement noise on estimation errors. The stability of the VS-ESMO is proved by backstepping control theory. An experiment is carried out on a 3.1 kW surface-mounted permanent magnet synchronous motor to validate the identification performance. The experimental results demonstrate that the VS-ESMO has a high estimation accuracy and fast convergence speed, and the identification value does not contain a chattering signal. Using the inertia and load torque identified by VS-ESMO for parameter tuning and compensation can improve system dynamic performance and anti-interference performance to the load.