Motion mitigation of hinged floating structures by adaptive control

System stability has been a crucial issue in design of very large floating structures. Large responses of floating structures not only deteriorate operation conditions but also seriously affect the safety, service life and maintenance cost of structures. In this paper, an idea of using hinge connection in control is proposed for stabilizing a five-modular floating platform. It leads to a great simplification in the deployment of thrusters on semi-submersible modules and only the control of heave, roll and pitch motions needs to be concerned. The motion equation of the floating structure is formulated in conjunction with a Proportional-Derivative (PD) control algorithm and an adaptive estimator for uncertain loads based on Radial Basis Function neural network (RBFnn). Sequential Quadratic Programming (SQP) is used to optimally distribute control thrusts. Numerical simulations verify the effectiveness of the proposed control method. •A control strategy with hinge connectors is proposed for motion reduction of multi-modular floating structures.•A neural network adaptive estimator for uncertain wave and connection loads is developed.•An optimization algorithm is applied to equally distribute the control output of thrusters.•The heave, roll and pitch motions of multi-modular floating structures are suppressed effectively.