Sensorless induction motor adaptive observer-backstepping controller: experimental robustness tests on low frequencies benchmark

In this study, experimental tests for an observer-based controller scheme are given to drive a sensorless Induction Motor (IM) even for the low frequencies case. Combining the advantages of a field oriented controller with the backstepping control method, a new robust controller is designed to track low frequencies trajectories. The static errors are eliminated using an integral backstepping technique, improving the robustness properties of the controller in spite of the uncertainties and the perturbations. An adaptive interconnected observer is designed for estimating fluxes, speed, load torque and the stator resistance in order to implement the controller. The knowledge of the stator parameter is crucial for sensorless control in particular to track low-speed trajectories when the observability property is lost. Practical stability based on Lyapunov theory has been proved to guarantee the strongly uniformly practical stability of the closed-loop system using the proposed observer-controller scheme. The tests are completed thanks to the reference trajectories of a specific sensorless IM benchmark where the robustness properties are validated under parameter variations and in presence of disturbances even for the low frequencies case.