Research On Robust Synchronization Control For Supply Ship During Underway Replenishment

The underway replenishment operation of ships is an operation where fuel,food,parts or personnel are transferred from one ship to another while both ships are moving.Replenishment of ships during navigation can shorten port time,provide favorable logistics support for long distance oceanic voyages,and thus increase the endurance and the operation range of ships.The synchronization control for the supply ship during underway replenishment is to design a synchronization control law and make it synchronously navigate with the supplied ship at a relatively fixed position on one side of the supplied ship in order to ensure the normal underway replenishment operation.Since the operational conditions and the ocean environment are constantly changing,there exist obvious uncertainties of the supply ship's dynamics and the environmental disturbances.During underway replenishment under uncertain disturbances,the supply ship needs to keep a certain safe distance from the supplied ship,and its output needs to be constrained within a certain range.Because of the inherent physical limitation of the ship propulsion system,the control forces and moment produced by it could be constrained.In addition,the velocities of the most ships are usually unmeasured.Therefore,it is of great theoretical significance and practical application value to carry out the research on the synchronization control for the supply ship and to design the synchronization control law for the supply ship during underway replenishment.For the robust synchronization control problem of the supply ship during underway replenishment,the main research work of this paper is as follows.Firstly,considering the uncertain dynamics of the supply ship and unknown time-varying environmental disturbances,a virtual trajectory locating on one side of the supplied ship with a relatively fixed distance from the trajectory of the supplied ship is introduced,and a disturbance observer is constructed to estimate the compound disturbances induced by the uncertain dynamics and unknown time-varying environmental disturbances;Based on this,a robust synchronization control law for the supply ship is designed using the command filtered backstepping approach to make it track the virtual trajectory and hence realize the synchronization navigation between the supply and the supplied ships.Besides,considering the output constraints and unknown time-varying environmental disturbances,the error transformation method is employed to deal with output constraints,and an adaptive law is designed to estimate the bounds of unknown time-varying environmental disturbances;Then,an adaptive robust synchronization control law for the supply ship is designed using the command filtered backstepping approach to make it track the virtual trajectory and hence realize the synchronization navigation between the supply and the supplied ships.In addition,comprehensively considering unavailable velocities,input saturation,uncertain dynamics and unknown time-varying environmental disturbances,a high-gain observer is constructed to estimate unavailable ship velocities;An auxiliary design system is constructed to address the effect of input saturation;The adaptive radial basis function neural networks(RBFNNs)are used to approximate the dynamics of the supply ship;The adaptive laws are respectively designed to estimate the weights of the RBFNNs and the bounds of unknown time-varying environmental disturbances;Then,an output feedback adaptive robust neural synchronization control law for the supply ship is designed using the command filtered backstepping approach to make it track the virtual trajectory and hence realize the synchronization navigation between the supply and the supplied ships.Taking a supply ship as an example,the simulations of the above robust synchronization control laws are carried out using MATLAB/Simulink.The simulation results show the effectiveness of the designed robust synchronization control laws.