Feedforward And Feedback Optimal Tracking Control For Offshore Steel Jacket Platforms

Thispaperstudiesthefeedforwardandfeedbackoptimaltrack-ing controller, the feedforward and feedback optimal tracking controllerwith memory and the discrete feedforward and feedback optimal trackingcontroller under an offshore steel jacket platform subject to irregular waveforce. Details are as follows:Firstly, we study the feedforward and feedback optimal tracking con-trol for an offshore steel jacket platform subject to irregular wave force.Based on a linear exogenous system model of the wave force, a feedfor-ward and feedback optimal tracking control scheme is proposed such thatthe controlled output of the offshore platform is capable of tracking an in-troduced asymptotically stable system. The uniqueness and existence ofthe feedforward and feedback optimal tracking controller is derived. Thecontroller can be obtained by solving an algebraic Riccati equation andSylvester equations, respectively. The effectiveness of the proposed con-trol scheme is demonstrated by simulation results. It is found that the feed-forward and feedback optimal tracking controller is better than the feed-back optimal tracking controller in the vibration amplitudes of the offshoreplatform and the required control force.Secondly, we study the feedforward and feedback optimal trackingcontrol for an offshore steel jacket platform with control delay. Basedon a state transformation, the offshore platform system with control de-lay is first transformed into a delay-free system. Then, the uniqueness andexistence of the feedforward and feedback optimal tracking controller isderived. The controller can be obtained by solving an algebraic Riccatiequation and Sylvester equations, respectively. It is found through simula-tion results that the feedforward and feedback optimal tracking controller is better than the feedforward and feedbackoptimal controllerfrom thetwoaspects: the vibration amplitudes of the offshore platform and the requiredcontrol force.Thirdly, we study the feedforward and feedback optimal tracking con-trol for an offshore steel jacket platform subject to irregular wave force. Afeedforward and feedback optimal tracking controller is developed to at-tenuate the wave-induced vibration of the offshore platform. For the caseof the offshore platform with a control delay, a feedforward and feedbackoptimal tracking controller with memory is presented. The controllers canbe designed by solving an algebraic Riccati equation and Stein equation-s, respectively. It is found through simulation results that compared withthe classic state feedback optimal tracking control scheme, the proposedcontrol scheme is more efficient in attenuating the vibration of the offshoreplatform. In addition, compared with the feedforward and feedback opti-malcontrolscheme, theproposedcontrolschemerequireslesscontrolcost.