Predefined-Time Antidisturbance Control for Periscope-Type Coarse Pointing Assembly Under Multiple Disturbances

The coarse pointing assembly (CPA) is a key actuator for satellite laser communication. In actual laser alignment tasks over distances of thousands or even tens of thousands of kilometers, extremely high requirements are placed on the CPA's angle position-tracking precision and rapidity. However, the aforementioned ultrahigh performance requirements encounter multiple disturbances including satellite vibration, and friction torque from the drive motor. To this end, this article proposes a novel antidisturbance control with predefined-time performance to deal with this problem. First, by fully utilizing the prior information of disturbances, a refined predefined-time disturbance observer (RPTDO) is designed to quickly and accurately estimate these disturbances. Second, to accomplish simultaneous compensation and suppression of multiple disturbances, a predefined-time composite controller is presented based on the output of the RPTDO. Finally, the effectiveness and advancement of the proposed method are demonstrated by experimental results.