No Speed Sensor, High-performance Induction Motor Speed Control

Due to multivariable, nonlinearity, strong coupling and varying with temperature changes of the parameters of induction motor, it is difficult to find control methods with expected performance in IM drive system. In order to improve control performance, a lot of work have been undertaken to develop the speed controllers. Meanwhile, to achieve high performance speed control, it is necessary to apply close-loop control of speed. Generally, rotor speed is obtained by speed sensor. Speed sensor will make the control performance degraded. Therefore, many studies and researches, in the control of induction motor drives, have focused on improving performance of speed controller and eliminating the speed sensor from the control system.The main challenge of this paper is to introduce the speed control methods of induction motor and the estimation methods of rotor speed. Initially, the necessary background is provided to explain control methods, speed estimation algorithms and mathematic model of induction motor. Then three control algorithms are studied and discussed specifically:(1) Speed sensorless sliding-mode control for induction motor drives based on feedback linearization: a speed sensorless sliding-mode feedback linearization control scheme with load torque estimation is presented. Simple observers constructed from mechanical model of the motor are used to estimate flux, speed and load torque. Additionally, a continuous control term is introduced to eliminate chattering. The following are the advantages of this control scheme: the generated speed becomes a linear output with respect to the control states; the rotor flux and generated speed can be accurately controlled; the system is robust to matched and unmatched uncertainties.(2) Vector control-based speed sensorless control of induction motors using sliding-mode controller: in the control scheme, the sliding-mode control strategy is worked in conjunction with the field-oriented method to improve the speed controller performance. The rotor speed used in speed feedback loop is obtained by speed observer system based on the measurement of terminal quantities. The...