Abstract: A novel combined active-passive model of the floating raft isolation system is developed by employing substructure mobility approach. Based on mobility matrices of subsystem, a general mathematical description of active and passive control of complex floating raft isolation system is completed. The concepts of such control methods as machine control, raft control and full control are presented for the first time, and then their relationships are illustrated. The power transmission characteristics of active floating raft system are investigated under different control methods when minimizing power flow strategy is applied, and the behaviors of active forces of the actuators installed on the intermediate raft structure are discussed in detail, hence some valuable general active isolation design principles of floating raft system are presented.

Key words: Active control, Floating raft system, Isolation design