Current sensorless position–flux tracking controller for induction motor drives

An innovative indirect field-oriented output feedback controller for induction motor drives is presented. This solution is based on output feedback since only speed and position of the motor shaft are measured, while current sensors are avoided. This approach is suitable for low cost applications, where the position sensor cannot be removed to guarantee accurate position tracking.The proposed method provides global asymptotic tracking of smooth position and flux references in presence of unknown constant load torque. It is based on the natural passivity of the electromagnetic part of the machine and it guarantees asymptotic decoupling of the induction motor mechanical and electrical subsystems achieving at the same time asymptotic field orientation. Lyapunov analysis and nonlinear control design have been adopted to obtain good position tracking performances and effective torque–flux decoupling. The cascaded structure of the controller allows performing a constructive tuning procedure for speed and position control loops.Results of experimental tests are presented to demonstrate the tracking and robustness features of the proposed solution.