Research On The Control Allocation Of Pipe Laying Crane Dynamic Positioning System

Dynamic positioning is that the Ships or offshore platforms automatically use its ownvarious types of sensors to detect the deviation between the actual location and the targetlocation and influence of the external environmental forces (wind, waves and ocean currentetc), controller can calculate the required control and torque real-timely, keeping the ship atrequired position of sea level as much as possible to achieve positioning. The controlallocation unit is an important part of the dynamic positioning system. The unit can Output ofthe horizontal, vertical force and the heading rotation torque command according to thedynamic positioning controller, allocate the control for each controller reasonably. The controlallocation include control allocation management and control allocation method. In this paper,we use the deep water pipe laying crane "Offshore Oil201" as the research object andresearch on the control allocation of the dynamic positioning system.First, in this paper, we should set up mathematical motion model of the pipe-laying crane,that include the kinematic model,the dynamic model, the external environmental forces (wind,waves and ocean current etc),the propeller model, and the load of the pipe-laying operation.The control allocation is usually divided into Linear quadratic unconstrained controlallocation, Linear quadratic constrained control allocation and Nonlinear constrained controlallocation. We can establish mathematical model respectively and research on the controlallocation using the pseudo-inverse method, quadratic programming and sequential quadraticprogramming methods.Different modes have their own adaptive control allocation method, so far there is not amethod being the most appropriate for every modes. Therefore, we lead in the concept of thecontrol allocation management. It means in case of considering mode of the ship we use andmanage the thrusters reasonably. Control allocation management usually consists of ThrusterSelection, Thruster Groups, Thruster Biasing, High-Speed Modes.Finally, the PID controllers are designed for the research object. The controller calculatethe required thrust command according to the position and heading deviation and pass it to thecontrol allocation unit. the application of matlab software for pipe laying crane movement model simulation. The simulations about mathematical motion model of the pipe-laying craneare carried out by the application of matlab software. The simulations of three controlallocation optimization algorithm are given, and prove the success of using the three methodon control allocation. Their advantages and disadvantages are illustrated in the samecontroller and simulation environment. Also coefficient matrix effects of the objectivefunction to the control allocation are studied.