Research On The Thrust Allocation And Control Capability For Dynamic Positioning System Of Ocean Engineering Vehicles

Dynamic positioning system refers to a ship under the closed-loop control system,without the aid of mooring system, could continue to detect the ship’s deviation betweenactual and target position by the measuring system, and use its own propulsion device tocounter the outside disturbance forces which acting on the ship, so that the ship can keepnavigation or positioning and meet the requirements of heading, speed, etc. The thrustallocation and control capability calculation are the important parts of the research of thedynamic positioning system. Thrust allocation strategy is to satisfy the controller and theoptimization objective function requirement, through certain allocation logic to control itsthrusters generate force and moment, a DP capability plot gives visual impression of themaximum environment in which a ship was still able to maintain heading and positioning.This topic is a major achievement transformation project of hall of Jiangsu provincescience and technology, the research object is a trailing suction hopper dredger and a cablelaying ship. In the thrust allocation strategy research aspect: First, this paper introduces thecomposition of ship propulsion system, analysis the hydrodynamic interaction between thepropeller and hull, analysis the hydrodynamic interactions between azimuth thrusters, andput forward the solution. Then puts forward the establishment of mathematical model ofthruster and described a equivalent processing way to the ship equipped with more than onebow thruster; Second, The objective of the optimal thrust allocation is less energyconsumption, heading keeping, less thrust error and minimize largest thrust force, takinginto account the physical conditions of the thruster and set up the dynamic thrust region. Atlast, using the quadratic programming methods combined with disjunctive programmingtechniques to solve above problems.In the control capability calculation aspect: This paper establish environmentaldisturbance force model and work force model, analysis the principle of control capabilitycalculation and draw the DP capability plots. The DP capability plots are usually used in thedesign phase of a ship, to get an indication of its DP capabilities. They can giving the validreference for the choice and layout of the thrusters and also used when analyzing therobustness of the DP system.In this paper, part of the research achievements carried out the dynamic positioningexperiments with a dredger, and the experiments made a good result. Therefore, this paper to a certain extent has theoretical reference and value of engineering applications.