Intrinsic Speed-Sensorless Control of Induction Motor

A novel speed sensorless control technique for induction motors is presented. No “simplifying” assumption on the magnetic flux (such as known initial conditions, measurable rotor/stator fluxes) is considered and the load torque is assumed constant, but unknown, according to the usual industrial control problem. In the proposed solution, the natural stabilizing feedback between torque current and the mechanical dynamics is suitably “modulated” using adaptive control techniques. Main feature and novelty of the presented approach is that no explicit speed estimation is utilized to compensate for the load torque (in this sense, the solution is “intrinsic”). Local exponential stability of the resulting nonlinear time-varying tracking error dynamics is guaranteed, if a physically meaningful persistency of excitation condition is satisfied. Simulations results under significant operating conditions are provided.