Direct Torque-Control of PMSM Drive by Delayed Sliding Mode and Feedback Linearization Control Approach

In this paper, performance improvement of a direct torque-controlled permanent-magnet synchronous motor drive is achieved through a novel delay dependent controller. The method is based on a delayed sliding controller with exponential reaching law in the outer speed loop combined with a nonlinear feedback linearization based controller in the inner flux and torque loop. Delayed sliding mode controller guarantees fast reaching to the sliding surface and avoids unwanted chattering due to its continuous approximation of the switching term in the sliding law. Simultaneously, the feedback linearization deals with motor nonlinearities and facilitates linear controller design for torque and flux regulation. The proposed scheme is based on the Lyapunov approach and utilizes space vector pulse width modulation with optimized design parameters. It provides fast torque and flux control with diminished fluctuations, high torque at low speed, fast speed response and reduced stator current distortions. Theoretical analysis and simulation results on a Siemens servo motor (1FT7082-AF7) prove the merits of the method in considering flux, torque and speed control performance compared with the conventional direct torque control based methods.