Structure of the control system of a marine vessel in dynamic positioning mode and its software implementation

Currently, dynamic positioning and low-speed maneuvering systems are increasingly in demand and necessary for safe maritime activities. Dynamic positioning systems are widely used mainly in the oil and gas industry, but also in supply vessels, barges and drilling rigs, ocean liners, and cargo ships. The development and analysis of control systems for the effective operation of a ship's control system with dynamic positioning requires the use of a mathematical model of the vessel, on the basis of which a study of synthesized control systems is carried out. The article proposes a general structure for modeling the control system for a vessel with dynamic positioning. The control system is represented by a set of a control object (in our case, a marine vessel), a command input device, a control device (controller), and an information and measuring system. The article considers a mathematical model of plane-parallel motion of a vessel, describing the movement of a vessel in three generalized coordinates: surge, sway, and yaw. As an example, two types of vessels with different propulsion systems are considered: a vessel equipped with two aft azimuth thrusters and a bow tunnel thruster, and a similar vessel, but equipped with a bow azimuth thruster. The forces generated by the propulsion devices of ships are determined through the connection with generalized forces and moments via the thrust allocation matrix for the corresponding kinematic scheme. The given propulsion schemes provide the possibility of holding the vessel in dynamic positioning mode. The description of mathematical models is presented in the form of vector-matrix nonlinear differential equations. The mathematical apparatus used to represent mathematical models of ships allows the use of models for the synthesis and modeling of control systems. The structure of the software implementation of the control system, developed in the Matlab environment, a description of the developed modules, and simulation results are presented.