Simultaneous State and Parameter Estimation in Induction Motors Using First- and Second-Order Sliding Modes

We address the problem of meeting the requirements of controllers for the control of speed of induction motors, but under the constraint of not using speed and flux sensors: the so-called “sensorless” control problem. We offer an observer-based solution and present the design of two observers which provide motor speed, flux, and rotor resistance estimates simultaneously. Both observers, based on the rotor flux model in the stationary reference frame, are designed with inputs that enforce first- (conventional) and second-order sliding modes, respectively, on appropriately chosen switching surfaces. We present experimental results of the estimation procedure to demonstrate that only current and input voltage measurements are needed for accurate speed and flux estimation even in the presence of unknown parameters.