Robust speed control of an induction motor: an H∞ control theory approach with field orientation and μ-analysis

In this paper we present a robust speed control strategy for an induction motor under field orientation. The control framework employed properly represents the induction motor state-space model and its inherent variations, which are treated as structured uncertainties. Applying an H_∞, optimization methodology on this framework we derive a stabilizing controller to meet design objectives and then robust stability and performance against such variations are checked by using μ-analysis. No on-line tuning is required for the parameters of the derived controller, which is the dynamic system responsible to keep the rotor flux orientation as well as the speed regulation at design levels, irrespective of the motor operating points. A general methodology arose from the usage of the proposed strategy and simulated experiments showed satisfactory results for the robust speed control of an induction motor.