Research On Large Ship Course/Track Intelligent Fault-Tolerant Control

With the rapid development of science, modern engineering systems are developing to the direction of largescale and complication, so reliability has already been a key indicator. It needs to research and solve urgently that how to guarantee the system operation high-frequency, safety and reliable. Large ship takes four-propeller and two-rudder, so that its propellers and rudders have the function of redundancy. That provides functional redundancy for large ship's course/track fault-tolerant control. In actual engineering, a simple robust fault tolerant control is difficult to improve the control precision,either a simple reconstruction of fault-tolerant control is limited by the time-delay of fault diagnosis sub-systems. Considering that, this paper first put forward the theory of steps for fault-tolerant control of ship course / track. In which combined organically with the robust fault-tolerant control, fault diagnosis and fault-tolerant control reconfiguration, integrated intelligent fault-tolerant control system, so that can improve the performance of fault-tolerant control system implementation, as well as reduce the difficulty.Firstly,briefly described the development of the subject relative theories and the needs of large ship.And then introduced the entire conceptual framework and contents of the paper.The mathematical modeling study of ship motion is foundation and core of ship control and simulation. Analyzed large ship manoeuvrability, derived the non-linear motion simulation model and simplified linear control model of the ship horizontal in detail, and then gave formulas of the ship hydrodynamic. Meanwhile, in order to simulate the ship's maritime navigation sports gesture as accurately as possible, and provide the simulation platform for the design and verification of fault-tolerant control strategy, we have researched the model of ship's total resistance, of propeller thrust, of the rudder force and moment model and the rudder servo system simulation. And then got the mode of random disturbance force and torque simulation model of the marine environment,Secondly, based on failure mechanism, established the fault tree, and then decomposed the fault tree's minimal cut sets to discriminate all possible failure modes and weak links. Researched the method of fault-tree generation sample set, designed fuzzy neural network fault diagnosis device structure, learnt algorithm training sample based on improved FNN-BP neural network, and approached the boundary of faults classification, so as to formate many-to-many nonlinear mapping from the feature space to the fault. Simulation verificated the diagnostic accuracy and generalization ability of designed intelligent fault diagnosis, so that provided fault information support for fault-tolerant control strategy reconstruction.Again, this research was based on analytical redundancy for fault-tolerant control theory, including the robust fault-tolerant control and reconfigurable faul-tolerant control. Because of the ship motion with uncertainty, non-linear, time-varying parameters, we designed a normal operating mode controller as H₂ /H∞.Proposed a fault mathematic modeling method that unity of sensor and actuator. As there was great difference in system control models under four fault conditions of propeller, based on the Lyapunov asymptotic stability theory and Riccati equation respectively, derived the ship robust fault-tolerant control design method that based on state observer, and designed robust fault-tolerant strategy for the corresponding operating mode switch scheduling. Researched the sensor fault tolerant control loop compensation method and sensor reconfigurable strategy, then put forward a method of genetic algorithm optimizes reconstruction parameters, so as to ensure the dynamic performance system reconstructed. Reconstructed pseudo-inverse method on actuator to prove the feasibility of the system actuators reconstruction conditions and designed the system reconfiguration controller.And then, described the idea this research proposed first that fractional steps for fault-tolerant control.On the normal operating conditions, used H₂ /H_∞to resolve large ship's problem, such as parameter uncertainty, theoretical modeling error, and random disturbance. At the initial stage, used robust fault-tolerant control based on Lyapunov to ensure system bounded, so that intelligent fault diagnosis system had time to process. After fault information diagnosis and separation, reconstructed the control law based on diagnostic information to further improve the system's fault-tolerant control performance. And put forward a design scheme and algorithm design flow chart of large ship course / track fault-tolerant control.Finally,simulated a large ship course / track intelligent fault tolerant control system to compare the effectiveness of this fault-tolerant control strategy design. Simulated respectively the robust fault-tolerant control system and intelligent fault tolerant control system of large vessels course / track in conventional PID control and H₂ /H_∞robust control systems on the normal operating conditions, as well as four fault operating conditions. Simulation results showed it was better that adopt H₂ /H_∞robust control strategy. The result was that STD (ψ) decreased by 8.9%, STD (δ) decreased by 14.6% in average. In which ship course / track control is better when the bow wave oblique incident angle. The performance under intelligent fault-tolerant control was better than that under traditional PID control. The result was that STD (ψ) decreased by 6.8%, STD (δ) decreased by 16.2% in average. That confirmed the step-fault-tolerant control strategy can achieve better fault-tolerant control effect. At last, gave a comprehensive summary of the large ships course / track intelligent fault-tolerant control system analysis and integrated approach.