Semi-active Groundhook Control of Offshore Tension Leg Platforms Using TMD with Optimized Parameters and MR Damper Under Regular waves

The motivation and objective of the present study are to propose a semi-active control system for offshore tension leg platforms (TLPs) to mitigate the vibrations induced by regular wave loads. State-of-the-art indicates that not much work is reported on semi-active control of offshore TLPs considering potential nonlinearities for multiple hazards using a control algorithm, which is robust against uncertainties. A displacement based groundhook (DB-GH) control algorithm using tuned mass damper (TMD) and magneto-rheological (MR) damper is employed for the semi-active controller because of its robustness against parametric uncertainties and reliability. Optimized parameters of the semi-active TMD (SATMD) are obtained using constrained nonlinear optimization to achieve the best control performance. The flexibility of the groundhook control lies in its simplicity of implementation, computational efficiency and its demand for only two sensors in order to achieve the calculations of control forces. The scope of the present study is to demonstrate the efficiency of the proposed controller and investigate the effects of different influencing parameters. A TLP, reported in literature, is taken as an illustrative example. The non-linearly coupled dynamic responses of the structure-damper system is analysed and solved in time domain using MATLAB SIMULINK. The results show the SATMD performs quite satisfactorily in reducing the responses of the TLP in different critical conditions.