Active motion control of fixed offshore platforms using an extended state observer

This paper describes an investigation into the application of an active control strategy for reducing the motion of offshore platforms in waves. The simulated structure is augmented with an active mass damper with a passive component tuned to the natural frequency of the platform. An actuator force under feedback control is used to improve the performance of the device. Simulations with realistic wave loadings are conducted and the performance is compared with that achieved using a passive tuned mass damper. A robust output feedback control strategy is utilized, which includes an extended observer to simultaneously estimate the system states and disturbance force. It is shown that significant performance improvements can be achieved when compared with passive control devices, and that the application is feasible within practical constraints, at least for smaller platforms.