A novel speed estimator for induction motor based on Integral Sliding Mode current control

The paper presents a new speed estimation method for the induction motor. The speed estimator is made possible by a special current control scheme that is based on Integral Sliding Mode (ISM). The traditional method for synchronous d-q current control is to use PI controllers along with a decoupling compensator. Synthesis of the compensation voltages requires knowledge of the speed and motor parameters. In the ISM scheme, the PIs are complemented with sliding mode (SM) controllers. This structure offers comparable performance without knowledge of the speed signal. The SM controllers play the same role as the compensation voltages used in the traditional method. Based on this observation, the speed is estimated using the filtered (average values) of the SM outputs. The paper describes the ISM current control method and presents the structure of the speed estimator. Simulations results are shown for a 1/4 hp three-phase machine.