Research On Tracking Control Algorithm For Pipe-Laying Dynamic Positioning Vessel

With the "Marine Powers" dream proposed by China, exploring and developing to the resource in the deep ocean has been promoted to a new height, at the same time, vessel and ocean engineering technology are becoming hot spots for the researchers recently. Dynamic Position technology has been applyed in various kinds of ocean engineering works as a kind of positioning technology, with the advantages such as excellent mobile ability, reliability and uncontrained to the deep of the water etc. The vessels equiped with the Dynamic Position system can produce reasonable control command and make the ship maintain desired position and stem depend on its own thruster system,while pipelaying,the pipe-lay vessel need to tracking along the desired path slowly, so the pipe-lay vessel must cooperate with the DP system to have a better performance. On the basic of forward foundation,this thesis has done some works about the modelling of pipe-lay vessel and the pipe, designing of the observer and the controller of the DP system combined with the actual production detailedly, the main works are listed as follow:Firstly,a reasonable kinematics combined with the dynamic model of the DP ship together with the environment disturbance model contains wind, current and wave are developed for the pipelay operation. At the same time, a simulation system comprised by the above three parts of models is given, and simulation test results are shown based on the above model.Secondly, a S pipe model is established according to the pipe-lay characteristic, this paper develops a robotic pipe model suited for control tasks which can maintain the physical shape and the force balance between each element of the pipe, The developed model is on the form of the robot equation with minimal coordinates, thus the methods of controller synthesis and stability analysis can be applied directly, and then proposes a passive controller which can guarantee the stability of the system,then simulation proves the effection of the developed method.An accurate estimator is the foundation of an excellent control system, this paper proposes a nonlinear passive estimator for the parameter uncertain situation in the pipe-lay model. The estimator can not only estimate the unknown environment disturbance force but also measure the low-frequency position and velocity information of the vessel from the measurement which includes noise. This paper analyses the passive property of the velocity estimate loop and proves the stability of the system with Lyapunov theory. At last,simulation study proves the effection of the proposed estimator in solving the uncertain problem caused by the uncertain hydrodynamic parameter and estimating the low-frequency position and velocity information of the vessel with a high accuracy.Actually, considering the difference between the desired pipe path and the desired vessel path,assuming that the distance between the touchdown point to the stern of the vessel is invariable, the desired vessel position can be compute according to the touchdown point by coordinate transformation. To track along the desired vessel positon accurately,a kind of terminal sliding mode control with neural dynamic model method is proposed in this paper which solves the velocity, control force and moment jump problem in traditional control methods, taking advantage of the smooth and output bounded particularities of biological neural system, choosing the velocity error as the sliding mode surface, the controller is designed, the simulation study proves the proposed control method can not only guarantee the tracking accurancy, but also solves the velocity and force jump problem existing in traditional control ways, so that the pipe-lay vessel can tracking smoothly and stably, the safety of pipe laying work can be guarantied.