To improve the vibration suppression performance of LQR based real structural vibration control system, an amended disturbance observer design method was presented for an all-clamped stiffened panel with unmodeled error, harmonic effect and acceleration sensor noise. Then, a compound control strategy is proposed to suppress the structural vibration excited by external sinusoidal disturbance, via combing the amended DOB and the traditional LQR optimized by the chaos sequence. Both theory analysis and vibration control experiment results have shown good disturbances and measurement noise rejection performances of the proposed active vibration control strategy.