Research On Tracking Control For Dynamic Positioning Vessel Based On Non-smooth Search Route

Currently,many scholars has been attracted by the research of dynamic positioning(DP)system.For DP vessel sailing in the ocean,tracking control is very important.Therefore,the study tracking control is necessary.Up till now,researches on tracking control method of conventional tracking has been relatively mature.The task solution for DP vessel sailing on special tracking task based on the given non-smooth search band will be proposed,including the continuous guidance algorithm based on the non-smooth search route,the high-precision tracking controller based on pre-set performance function and backstepping sliding mode,and the tracking controller with yawing rate constraints and high-precision based on pre-set performance function.The main work of this paper is organized as follows:Firstly,the task description and problem analysis are proposed in detail,and the guidance algorithm is selected based on the solution obtained from the analysis.Through the analysis of the SFLOS algorithm which is not limited by the path,it is concluded that using the SFLOS algorithm can not finish tracking of the non-smooth search route.A guidance algorithm of non-smooth search route based on TTG is designed.Finally,the simulation of the smoothed search route based on TTG algorithm is carried out.The simulation result shows,the disadvantage of SFLOS algorithm is that the requirements for simulation step size are relatively strict,and the actual desired heading control effect is poor.Above all,The TTG algorithm is selected to design the controller.Secondly,aiming at the requirement of high-precision tracking task for DP vessel based on given non-smooth search route.A sliding mode controller for DP vessel based on pre-set performance function is designed to satisfy the requirement of high-precision.First of all,considering about the environmental disturbance,the sliding mode principle is added to the backstepping controller.The robustness of the sliding mode controller is used to reduce the influence of the environmental disturbance.The tanh function is selected to replace the traditional sign function,which effectively suppresses the chattering of the control signal.An improved sliding mode controller is designed to make the speed change of DP vessel more stable.Based on the backstepping controller with sliding mode,a controller based on pre-set performance function is designed,which restricts the error of north and east position and heading angle,which can also limits the error to the boundary of performance function.Finally,the simulation results show that the robustness of the backstepping controller with sliding mode can resist the environmental disturbance to a certain extent,and the improved sliding mode controller can make the speed change of DP vessel more stable and prevent the occurrence of input saturation to a certain extent.The backstepping controller with sliding mode based on the pre-set performance function can fulfill the control requirements of high-precision tracking and the convergence speed is faster.Finally,according to the requirements of high-precision tracking control task with yaw rate constraint,a backstepping controller with sliding mode based on pre-set performance function and i BLF function is designed.First of all,a backstepping controller with sliding mode based on BLF function is designed to restrain the yaw rate error.Similar to BLF function,a controller based on i BLF function is designed to restrain the yaw rate.Then,combining the IBLF function and the pre-set performance function,a controller is designed to satisfy both high-precision and the yaw rate constraint.Finally,the simulation results show that the controller based on i BLF function can constrain the yaw rate in the whole constraint space,while the BLF function can only constrain the yaw rate in the subspace of the constraint space and it has a high limit on the initial feasible solution.The backstepping controller with sliding mode based on the pre-set performance function and i BLF function has the advantages of i BLF function and pre-set performance function at the same time.It can make the DP vessel trace on the given non-smooth search route with high-precision,faster convergence speed,strong robustness,good security under the condition of yaw rate constraint.