Robust Speed Regulation of Induction Motor Subjected to Unknown Load Torque

Abstract

Induction motors are still the most used in industrial applications due to the simplicity of installation and low maintenance cost, especially for the squirrel cage type. The significant development in power electronics in terms of high-speed technologies in power electronic switches, their availability in high ratings, and the considerable decrease in the cost of the power electronics components supports this increase in uses. However, changing the induction motor's speed with loading, load torque measurement devices, and speed sensors limit this increase in using such motors. This paper proposes a state feedback controller-based backstepping technique for robust speed regulators of induction motor loaded without measuring the load torque. Designing such a controller (state feedback controller) needs to know the value of the load torque, and hence torque values ​​are assumed to start the design process. A state observer as output feedback is integrated into the speed controller proposed in this paper instead of load torque measurement. To asset the proposed controller's capability to keep the induction motor speed at the desired value, the global stability is investigated using Lyapunov direct theorem. The simulation results show that the proposed method's effectiveness in keeping the motor speed at the desired value without load torque measurement.