Research On Fault Diagnosis And Fault Tolerant Control For Longitudinal Stability Of Trimaran

As a type of ships with high stability and seakeeping,the high-fast trimaran has become a research hot-spot in recent years.Based on the parameters of an actual trimaran equipped with T-foil,the design of fault diagnosis observer and robust fault-tolerant controller of the trimaran longitudinal motion in the condition of wave disturbances have been studied.The stability control of the longitudinal motion has been finally realized.First of all,the coordinate system was established and the analysis of hydrodynamic forces of the longitudinal motion of trimaran was also carried out.With the analysis of the random wave model and the forces provided by the T-foil,the longitudinal motion model with input constraints of trimaran has been obtained.Then,a fault diagnosis problem for the longitudinal motion of a trimaran with wave disturbances has been proposed.Based on the H_-/H_?optimization index,the robustness and sensitivity of the diagnosis system were described.Furthermore,the problem of solving state observer has been transformed into performance index optimization.Finally,the observer gain matrix with optimal performance was obtained by solving Liner Matrix Inequality(LMI).It can be determined whether the fault occurs or not in the system by comparing and analyzing the designed threshold and the residual evaluation function.Next,one kind of robust fault-tolerant controller design for a breakdown-admitted trimaran system has been carried out.A mathematical model of the sensor-fault trimaran system with parameter perturbations was established.Combined with requirements of Lyapunov stability,the necessary and sufficient conditions for the robust stability of the closed-loop system in the form of linear matrix inequalities were given.Here all possible cases of sensor failures were discussed.The controller reconfiguration was adopted to design the robust fault-tolerant controller online.Finally,the Model Predictive Control was introduced to redesign the robust fault-tolerant controller.According to the rolling constraint optimization,the design problem of robust fault-tolerant controller was transformed into finding a feasible solution which satisfies the minimum of objective functions.Finally,the necessary and sufficient conditions for the robust stability of the closed-loop system under the predictive control algorithm were given in the form of linear matrix inequalities.The controller was reconstructed online by solving linear matrix inequalities.According to the actual trimaran parameters,the proposed methods were verified by simulations.The results have shown that the designed fault diagnosis observer not only ensures the robustness to interference signals such as wave disturbances and model uncertainty,but also has sensitivity to the fault signals.Above two methods of designing robust fault-tolerant controller has restrained the longitudinal movement of the trimaran and realized the longitudinal motion stability of the trimaran with sensor failures.The simulation results proved the feasibility and effectiveness of proposed methods.