Elegant Anti-disturbance Control For Dynamic Positioning Ships With Thruster Faults

The accuracy of ship motion control is influenced by ocean environmental disturbances(ED)such as currents,waves,and winds.Ships using dynamic positioning(DP)systems can availably raise positioning accuracy and enhance the availably of offshore development.However,the thrusters exposed to the marine environment for a long time will inevitably have unpredictable faults,which will affect the positioning accuracy of the DP system for ships.Therefore,the reliable anti-disturbance control of DP system has received extensive attention.Based on this background,this paper has carried out the research on the elegant anti-disturbance control(EADC)of ships with different thruster faults.The main content is the following three parts:In part one,the problem of anti-disturbance control for ship dynamic positioning systems with slowly-varying ED and modeling uncertainty under loss-of-effectiveness(LOE)faults are studied.To solve this problem,an EADC strategy is proposed by combining DOBC with adaptive fault-tolerant control(AFTC),which can simultaneously compensate for the ED and the thruster faults.In addition,a robust control term is introduced to suppress modeling uncertainties,thereby reducing the impact of uncertainty on positioning control performance.Under the proposed EADC strategy,the dynamically positioned ships can reach the prescriptive position and heading.In part two,the problem of anti-disturbance control for ship dynamic positioning systems with unknown ED and modeling uncertainty under thruster faults are studied.An adaptive disturbance observer(ADO)is established to evaluate ED.Based on the disturbance estimations,an EADC control strategy is proposed by combining it with robust adaptive control and AFTC.Under the proposed EADC strategy,both the disturbances and the faults can be compensated and suppressed simultaneously,enabling the controlled ship to reach the predetermined position and heading.In part three,the problem of anti-disturbance control for ship dynamic positioning systems with and input saturation dynamic input under thruster faults are studied.An ADO is established to estimate ED.A command filtering based EADC strategy is proposed based on the ED evaluation combined with AFTC.The introduction of intermediate dynamic system solves the negative impact of input constraints on the systems.Command filtering eliminates the dynamic input problem and ensures the high anti-disturbance control accuracy of the DP system.Under the proposed EADC strategy,dynamically positioned ships can reach a given position and heading.