Direct torque control via feedback linearization for permanent magnet synchronous motor drives

The paper describes a direct torque controlled (DTC) permanent magnet synchronous motor (PMSM) drive that employs feedback linearization and uses sliding-mode and linear controllers. We introduce a new feedback linearization approach that yields a decoupled linear PMSM model with two state variables, the torque and the square of stator flux magnitude. This linear model is intuitive and allows the implementation of DTC-type controllers that preserve all DTC advantages and eliminate its main drawback, the flux and torque ripple. Next, we investigate two controllers for toque and flux. A variable structure controller (VSC) which is robust, fast, and produces low-ripple control is compared with a linear-DTC scheme which is ripple free. The torque time response is similar to a conventional DTC drive and the proposed solutions are flexible and highly tunable. We present the controller design and analyze the robust stability. Experimental results for a sensorless PMSM drive validate the proposed solution.