Research On The Method Of Dynamic Positioning Ship Propulsion System Fault Tolerant Control

With the continuous depletion of land resources, people started to focus on the resourceful ocean. However, the development and exploration of marine resources often need high-tech marine equipment and this demand accelerated the development of deep-sea equipment continuously. As a sword in deep-ocean exploitation,dynamic positioning(Dynamic Positioning, DP) system has been more and more popular. Considering the safety and reliability of ship,in modern dynamic positioning system,there exists physical hardware equipment redundancy and control software analytical redundancy. When the system equipment faults, the physical redundancy equipment is adjusted through analytical redundancy relationship to achieve the goal of fault-tolerant control. The failing systems after fault tolerant control are still able to meet the requirements of certain condition.In this paper, the fault diagnosis and fault tolerant control of DP ship propulsion system are studied. The method of fault diagnosis and fault tolerant control of a certain type of DP ship is verified. The specific contents are as follows:Firstly, the dynamic model and kinematic model of DP ship is established, and the propulsion system is introduced. The parameters of the ship model are given, and the model is verified through simulations.Secondly, the possible fault types, fault features and possible consequences of the DP ship propulsion system are introduced, and the fault types and data analysis of the fault diagnosis can be better provided by the introduction of this part.Then, the fault diagnosis problem of DP ship propulsion system is based on the adaptive sliding mode observer for global fault diagnosis method for local fault diagnosis. The main reasons are that the DP ship is strongly coupled because of multiple propellers, and the global fault diagnosis is not able to accurately determine the fault location. The fault diagnosis of the sliding mode observance is verified by simulation. Qt is used to establish the fault diagnosis platform for the BP neural network part and fault type can be determined effectively.At last, when it comes to fault-tolerant control with propeller malfunction, according to the fault diagnosis results, the output saturation problem in practical engineering is considered and the nominal controller is still kept in the control loop at the same time. The fault tolerant control method of input saturation adaptive sliding mode virtual actuator is used to control the fault system. Reconstructing and adjusting the nominal controller caused by malfunction becomes unnecessary in the proposed method. The proposed method solves the uncertainty, nonlinear, model error and external disturbance problems of the system based on sliding mode control and adaptive control. The virtual actuator is placed in the middle of the fault of the ship and the nominal controller to reconstruct the control signal, so that the fault of the ship can still get the desired output under the influence of the reconstructed signal. The feasibility of the method to solve the problem of fault tolerant control of thruster fault is verified by simulation.