Research On Thrust Allocation Algorithm Of Ship Dynamic Positioning System

With the growing demand of various resources of sea for human, the scope of activities for people has extended from the coast offshore to deeper waters. At the same time ship dynamic positioning system will get a great development. As an important part of the ship dynamic positioning system, thrust allocation will play an important role. Thrust can be more accurately allocated based on the understanding of the propeller type and installation location. In this paper we propose an economic, reliable and practical method of solving thrust allocation to the 2.8 m ship model installing two tunnel thrusters and two azimuth thrusters based on the pseudo-inverse algorithm.Firstly, this article lists the difference between dynamic positioning thrusters and conventional propulsion thrusters and gives a variety of typical ship thrusters and a brief introduction characteristics of various thrusters as a reference for the selection and installation location of the ship thrusters, that provides a basis for the solution of the thrust allocation algorithm.Secondly, this article establishes a mathematical model of the thrust allocation based on thrust allocation problem, and gives optimization objectives of optimization algorithm and various constraints according to the needs of the actual system.Thirdly, this article introduces the theoretical basis of thrust allocation algorithm based on the pseudo-inverse method and proposes static and dynamic combination for quadratic optimization of thrust allocation algorithm based on the pseudo-inverse method. Select the appropriate weight matrix depending on the power of the thrusters can allow thrusts mainly distributed in azimuth thrusters of the stern. This thrust allocation method can make the minimum energy consumed. Taking into account banned angle of azimuth thrusters, the change rate of azimuth angles, thrust limit, singularity structure and so on, the error is smaller. Taking into account the actual situation of the ship model system, an optimization thrust allocation algorithm based on the pseudo-inverse method also can quickly get stability solutions and will be more concise, reasonable and also meet the above conditions.Finally, this article introduces the concept of ship dynamic positioning capability curve. It expresses dynamic positioning capability of the ship under specified thrust system parameters and environment and the main representation method is limit wind speed curve. This article draws out the dynamic positioning capability curve based on pseudo-inverse thrust allocation algorithm. It not only analyzes positioning capability of the ship dynamic positioning system, but also provides a reference for the design of the ship dynamic positioning scheme.