Performance Improvement of Sensorless Direct
Field Oriented Induction Motor Drive with Sliding Mode and Fuzzy Sliding Mode Controllers

Abstract

For high performance, variable speed applications, the Induction Motors are used widely due to its low cost, low maintenance, requirement, robustness and reliability, thus replacing the DC motor drives. For wide range of speed applications and fast torque response, IMs perform
satisfactory with the vector control strategy. Because of the higher order unmodeled system dynamics and different machine parameters such as rotor speed, stator and rotor resistance variation and load torque variation, different nonlinear controllers are used to increase its robustness and to make the system stable. However, the use of linear controller does not give satisfactory performance due to the above causes. IM is mathematically to get an approximate idea of the actual plant model. The vector control of IM is implemented by using different controllers such as P-I, sliding mode controller and a hybrid controller such as fuzzy sliding mode controller. To make the system to remain in steady-state, P-I controller is used and due to the more sensitive action of the derivative controller, it is not used. The sliding mode controller is designed for robust control of IM. Under different adverse condition, its performance is satisfactory. But, the main disadvantage of sliding mode controller is the chattering problem that can be reduced by taking necessary steps. The disadvantage of the sliding mode controller is eliminated by a hybrid controller such as fuzzy sliding mode controller. To make the system sensorless, we go for rotor speed estimation using direct synthesis of state equation, as the closed loop control requires the speed sensor. By using speed sensor, the IM becomes more costly and less reliable and increased maintenance cost. The different simulation results are observed and studied and the analysis of the different simulated results are presented.