Research On Fuzzy Control Schemes For Offshore Platforms

This paper mainly deals with fuzzy control schemes of off-shore steel jacket platforms subject to external wave forces and nonlinear self-excited wave forces.The main points are:Firstly,an active feedback H_?fuzzy control scheme for offshore plat-form is studied.First of all,by considering the parameter perturbation-s of the platform mass and active mass damper mass,a Takagi–Sugeno(T-S)fuzzy model is established for offshore platform subject to external wave force.Then an active feedback H_?fuzzy control scheme is designed based on parallel-distributed compensation scheme.An existence suffi-cient condition of the fuzzy control law is derived,the stability and H_?performance of the system are analysed.At last,by numerical simulation,the H_?fuzzy control scheme is compared with the conventional H_?control scheme,which is proved that the proposed scheme can improved the con-trol performance more significantly,while the former requires less control cost.Secondly,a pure delayed H_?fuzzy control scheme of the offshore plat-form is researched.First of all,by introducing time-delays intensionally into control channel,a pure delayed H_?fuzzy control scheme is designed based on the T-S model established in the first part.Then,an existence sufficient condition of the fuzzy control law is derived,the stability and H_?performance of the system are analysed.At last,by numerical simula-tion,the delayed fuzzy control scheme is compared with the method men-tioned in the previous part,which is proved that the the proposed scheme can improved the control performance more significantly,while the former requires less control cost.Thirdly,a delayed robust H_?fuzzy control scheme for offshore plat-form is studied.First of all,by applying T-S fuzzy method to approximate the nonlinear term,a T-S fuzzy model is established for uncertain offshore platform system subject to external wave forces and nonlinear self-excited wave forces.Then,a delayed H_?fuzzy control scheme is designed.An ex-istence sufficient condition of the fuzzy control law is presented,the stabil-ity and H_?performance of the system are analysed.At last,by numerical simulation,the proposed scheme is compared with the conventional de-layed H_?control scheme and the pure delayed H_?fuzzy control scheme,which is proved that,(i)for the uncertain system,the control performances of the delayed robust H_?fuzzy control scheme are improved more signifi-cantly than those of the conventional delayed robust H_?control scheme and the pure delayed robust H_?fuzzy control scheme,while the control cost of the former is reduced;(ii)for the nominal system,the control performances of the delayed H_?fuzzy control scheme are improved more dramatically than those of the conventional delayed H_?control scheme and the pure delayed H_?fuzzy control scheme,while the control cost of the former is reduced dramatically.