Simplified exponentially convergent rotor resistance estimation for induction motors

One of the main problems in induction motor (IM) control is the lack of knowledge about the actual value of the rotor resistance, which is subjected to large variations during operation. Due to the unavailability of the rotor electrical quantities, it is not easy to define an error signal suitable to be used as "engine" for the identification mechanism. We propose two adaptive/variable-structure identifiers based on different standing assumptions, both providing an exponentially convergent estimate of the rotor resistance. The high simplicity of the overall schemes, and the low dimension of the regressor vectors (which leads to mild persistence-of-excitation requirements) constitute the main positive features of the proposed approach. Simulation results are provided.