Stable inertia identification considering precise cogging torque under low-speed operation

Committed to the fact that the cogging torque of permanent magnet synchronous motors (PMSMs) under low-speed operation severely aggravates the speed ripple as well as the identification performance of inertia, this article puts forward an interconnection network (IN) using three extended sliding-mode observers (ESMOs) for the precise identification of both inertia and cogging torque. Difference from existing parallel observers, an adaptive-reaching gain (ARG) for each observer is designed to fully exploit the identification performance while minimizing undesirable low sliding-mode tremors. Moreover, a constraint criterion is adopted to limit the ARG for the IN's stability. By constructing an auxiliary function, more notably, the first ESMO in this IN is capable of identifying the cogging torque's eigenvalue online, which allows its mathematical model to be, thoroughly, linearized. Meanwhile, the second dual-state ESMO to observe its model parameters, where a tradeoff activator is exploited to suppress the coupling effect caused by estimation errors between the dual-state items, is combined for facilitating the accurate cogging torque. Finally, a stable inertia observed by the third ESMO is guaranteed via this IN. The advantages of the proposed scheme are verified by experimental results.