Sensorless speed estimation of linear induction motor under variable discrete loading using cascaded MRAS observer

Abstract

This paper presents sensorless speed estimation scheme for Linear Induction Motor (LIM) using Cascaded MRAS Observer. Initially, LIM is represented by its state space model including the end effects. Next, the thrust due to end effect and the external load is modeled as a quadratic function of motor velocity. One of the parameters of the quadratic cost function is tuned according to adaptive laws, which forms a part of the adaptive mechanical system based on thrust model. The speed estimated from the mechanical model, is then fed to the adaptive current model of the motor which generates rotor flux vectors. These rotor flux vectors are compared with the reference rotor flux vectors to generate an error signal, which is conditioned according to adaptation laws. The adaptation scheme is based on PID and SMC laws. The above algorithm has been implemented using Matlab/SIMULINK platform and gives satisfactory results under different operating conditions.