Abstract
In this paper, a model reference adaptive system (MRAS) based super-twisting sliding-mode-based speed observer (STSM) with direct torque control (DTC) strategy of a squirrel cage six-phase induction motor (SC6PIM) for ship propulsion application is presented. The flux estimator is based on the super-twisting (ST) approach which is a second-order SM technique. This estimator is employed as a reference model in the MRAS based-speed observer to get rid of the problem of chattering in the traditional sliding mode (SM) approaches. The STSM controller is employed at the speed, stator flux, and at the torque control loops of SC6PIM to enhance the syatem performance during external load disturbances. In addition, the STSM observer estimates the stator flux and torque with providing a robust performance without the consequences of high chattering problem. The performance of the proposed MRAS-based STSM observer is investigated experimentally for a 750 W SC6PIM and compared with conventional MRAS observer during different speed commands, and low speed command and low load torque conditions.