Design Of Robust Control System Based On New Disturbance Observer

As for the problem that the actual plants inevitably exist model uncertainties, external disturbances and measurement noise, this paper mainly researches for disturbance observer-based robust control. Because the traditional disturbance observer structure is mainly used for minimum phase plants and its effect of suppressing high frequency is not well. So, an improved disturbance observer based control structure is put forward, which can suit for non-minimum phase plants. It has two degrees of freedom control features, and the design of controllers can be divided by two separate phases: one stage is performance design (nominal cost controller design), the other is robustness design (design of disturbance observer ). Hence, the mutual restriction of contradictions between system performance and robustness are eliminated.On the basis of traditional disturbance observer structure, the improved disturbance observer control system adds a new structure for compensating the feedback signals of system output. When there exist model uncertainties, any external disturbances or measurement noise, the performance controller output and the feedback signals of system output can be dynamically compensated in real time. Hence, the effect of the external disturbances in low frequency and the model uncertainties in system output are eliminated. Furthermore, the capability in suppressing high frequency measurement noise is highly improved. Whether there is any disturbance, the law of nominal performance controller can maintain unchanged. And disturbance observer-based closed-loop control structure is equivalent to open loop control, organized by an controller adding with a disturbance observer structure.This paper has analyzed the basic principles of improved disturbance observer control and design of parameters. The design of control parameter is so simple that the system robustness against external low-frequency disturbances and high-frequency measurement noise through a low pass filter and high pass filter design. At last, MATLAB simulation results show the effectiveness of the improved disturbance observer control structure enhancing control system robustness against disturbances.