Abstract: Spacecraft is a kind of complex coupling rigid and flexible system composed of free fly center rigid body connected with flexible appendages (such as sun plate，space robots etc.) by flexible joint, the problem of vibration will be caused when slewing or external disturbance excitation, which will affect the stability and the pointing accuracy of the system. Based on modal theory, the dynamics model of the coupling rigid and flexible structure including flexible link and flexible joint is built up and written in state space form, and controllability is analyzed. The combining PPF (Positive position feedback) and PD (Proportional dervative) control law is presented to suppress the vibration of the flexible structure, and the stability and control performance are analyzed theoretically. The experimental setup of the coupling rigid and flexible structure is designed and built up, and the active vibration control re-searches are developed including set point vibration control and slewing vibration control. The experimental comparative research results verify that the presented methods can suppress the vibration quickly.

Key words: Active vibration control, Combined PPF and PD control, Coupled rigid and flexible, Flexible joint, Flexible structures, ystem