On vibration rejection of nonminimum-phase long-distance laser pointing system with compensatory disturbance observer?

This paper focuses on the vibration rejection problem for the nonminimum-phase long-distance laser pointing system on the moving platform. Due to the unstable approximate inverse of nonminimum-phase property, the disturbance-observer based control (DOBC) methods inevitably sacrifice numerous vibration rejection capabilities to stabilize the system. In this paper, a compensatory disturbance-observer-based control (CDOBC) method is proposed to ensure a much stronger vibration rejection performance. In this method, the stable nominal plant replaces the unstable approximate inverse. Limited by stability constraints, the primary filter still sacrifices performances to provide basic vibration rejection capabilities. In the premise of a stable primary filter, the proposed compensatory filter naturally and effectively satisfies its stability constraint. Thus, the novel compensatory filter has sufficient flexibility to make up for the sacrificed vibration rejection capabilities of the primary filter without breaking the system?s stability. The CDOBC method has quite enough capability to reject the vibrations of the nonminimum-phase long-distance laser pointing system, which is impossible for the DOBC methods. Furthermore, the analytical system?s stability and tuning laws for the proposed method are presented. The simulations and experiments demonstrated the effectiveness of the proposed method despite various vibrations.