This paper proposes a novel robust design method of the full-order observer for vector controlled induction motors. The full-order observer has been widely employed to estimate rotor flux, but pole location for robust flux estimation against parameter deviations has not been clear unfortunately.
In this paper, robust flux estimation problem is regarded as a phase shaping problem of a transfer function because it is the most important for the vector control to suppress axis deviation. Accordingly, the proposed design method utilizes γ-positive real problem, gain-scheduled H_∞ control and linear matrix inequality technique so that axis deviation might be suppressed against parameter deviations at all operating point. Robust performance of the proposed method is evaluated by the frequency response function. Finally, feasibility and effectiveness of the proposed method are shown by experimental results.