A methodology is presented for implementing the nonlinear active control of compliant offshore platforms, such as the articulated leg platform (ALP), using feedforward and feedback gain (open-close loop) strategy. The nonlinear control law is derived by minimizing a higher order performance index, expressed as a function of the state variables and the control force. The state variables include angular displacement and velocity of the tower, and also the sea surface elevation and its integrands. The degree of nonlinearity of the control force is regulated by incorporating a nonlinear weighting factor in the control law. Both controlled and uncontrolled responses of the ALP are obtained by an iterative frequency domain technique which duly considers all the nonlinearities involved in the system. The response of a 180.5-m ALP is obtained for a random sea state under different, important parametric variations and is compared with those obtained by other control strategies.
Nonlinear open-close loop active control of articulated leg platform
International Journal of Offshore and Polar Engineering ; 9 , 2 ; 141-148
1999
8 Seiten, 24 Quellen
Article (Journal)
English
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