OPEN-CLOSE LOOP ACTIVE CONTROL OF ARTICULATED LEG PLATFORM

A method is presented for the active control of the articulated leg pl atform (ALP) idealized as a single-degree-of-freedom (SDOF) system, us ing a combined feedforward and feedback (open-close loop) algorithm. T he linear active control strategy is adopted to obtain the controlled response. The control law is derived by minimizing a quadratic perform ance function of the state variables and the control force. The state variables include not only the structural responses but also the sea-s urface elevation and its integrands. The controlled responses are dete rmined by a frequency domain iterative technique that duly accounts fo r the different kinds of nonlinearities present in the system. A singl e-hinge ALP in a random sea state is analyzed to obtain the controlled responses using the proposed method under a set of parametric variati ons. The controlled responses are compared with those obtained by the conventional feedback active control (close loop) strategy to investig ate the relative merits of the proposed algorithm.