Research On Cooperative Positioning Control Of Multiple Dynamic Positioning Vessels

As an important tool in marine exploration and exploitation,dynamic positioning(DP)vessels are widely used in marine engineering operations.With the increasing types of offshore engineering operations,a single DP vessel cannot meet the requirements of complex tasks due to its limited operational capacity,such as marine emergency rescues,installation and decommissioning of large offshore structures,and positioning unactuated floating obj ects.To accomplish these tasks,multiple DP vessels are required to perform cooperative positioning operations.Therefore,the research on cooperative positioning control of multi DP vessels has significant practical application values.Under this background,the dissertation focuses on the cooperative positioning control of multiple DP vessels,where some practical issues are considered,including time-varying environmental disturbances,model uncertainties,input saturation,unavailability of velocity measurements,and positioning unactuated floating objects.The specific research contents are as follows.For the cooperative positioning control problem of multiple DP vessels with time-varying environmental disturbances,cooperative positioning control methods based on disturbance observers are proposed.Firstly,a disturbance observer is introduced to estimate time-varying environment disturbances.Based on graph theory and the dynamic surface control(DSC)technology,a cooperative positioning controller is proposed.Secondly,to improve the estimation performance of time-varying environmental disturbances,a finite-time disturbance observer is designed.And considering the control input saturation constraint,an auxiliary dynamic system(ADS)is constructed.Then,an anti-saturation cooperative positioning controller is devised.Thirdly,it is proved that the cooperative tracking errors are bounded via the Lyapunov stability theory.Finally,simulation results verify that the proposed control methods can accurately estimate environmental disturbances,reduce the oscillation and saturation time of control input,and achieve high cooperative positioning operation precision.To solve the cooperative positioning control problem of multiple DP vessels with model parameter uncertainties and time-varying environmental disturbances,neuroadaptive cooperative control methods are proposed.Firstly,a neuroadaptive estimator is designed to estimate the lumped disturbances that consists of model parameter uncertainties and disturbances.Secondly,a state feedback anti-saturation cooperative positioning controller based on the ADS is devised to handle input saturation.In particular,a second-order linear tracking differentiator is introduced to avoid directly taking the derivative of the kinematics control law and sensitivity to noise in traditional DSC,and obtain the smooth kinematics control signal.Thirdly,considering that the velocity measurement is not available in practice,a neuroadaptive state observer is designed to estimate the velocity information and lumped disturbances.Based on the estimation values,an output feedback anti-saturation cooperative positioning controller is proposed.Thirdly,it is proved that the cooperative tracking errors are bounded via Lyapunov stability theory.Finally,simulation results verify that the proposed cooperative positioning control methods can estimate the lumped disturbances well,reduce the output oscillation in the initial stage,and have better dynamic quality and higher steady-state cooperative positioning accuracy.For the cooperative positioning control problem of multiple DP vessels connected to an unactuated floating obj ect through towlines under model parameter uncertainties and time-varying environmental disturbances,cooperative positioning control methods for multiple DP vessels are proposed based on time-varying relative positions.First,the time-varying relative positions are designed according to the control force required by the unactuated floating object,the control allocation algorithm,the towline model,and the towline attachment geometry on the floating object.Secondly,based on the state information of neighboring vessels,the designed time-varying relative positions,and an adaptive law,a robust state feedback cooperative positioning controller is devised using DSC.Thirdly,considering that the velocity measurements of the object and DP vessels are not available,nonlinear extended state observers(NESOs)are designed to estimate the velocities and the lumped disturbances.And considering the control input saturation constraint,an output feedback anti-saturation cooperative positioning controller is developed based on the ADS.In particular,the designed NESOs only need to adjust one parameter,which can simplify the parameter adjustment process in practical application.Thirdly,it is proved that all signals in the closed-loop system are bounded by using the Lyapunov stability theory.Finally,simulation results verify that the proposed control methods can improve the positioning accuracy of the unactuated floating object,smooth the towline tension,and have better robustness.In this paper,some control problems of cooperative positioning operation for multiple DP vessels are investigated,and the stability analysis and simulations of the designed control methods are carried out.The results show that the designed cooperative positioning control methods based on disturbance observers can deal with disturbances and input saturation well,and achieve high-precision cooperative positioning operation of multiple DP vessels.The designed neuroadaptive cooperative positioning control methods can further achieve high-precision cooperative positioning operation of multiple DP vessels with model parameter uncertainties and unavailable velocity measurements.The designed cooperative positioning control methods based on time-varying relative positions can improve the positioning accuracy of the unactuated floating object.