Sliding-Mode Sensorless Control of Direct-Drive PM Synchronous Motors for Washing Machine Applications

A new sensorless field-oriented control of direct-drive permanent-magnet synchronous motors based on "sliding mode" has been studied and applied to domestic washing machine drives. To achieve speed control requirements for the application, a novel sliding-mode observer has been developed by applying the technique of feedback of the "equivalent control." Armed with the developed algorithms, this observer is able to minimize the estimation error of rotor position at low speeds and guarantee fast convergence of the observer at high speeds in the flux-weakening region. As such, this sensorless control is suitable for domestic washing machine drives demanding wide-speed-range operation. The proposed sensorless control algorithms are implemented in a cost-effective digital controller and tested in a selected prototype washing machine. Both computer simulation and experimental results are illustrated for verification.