The Longitudinal Motion Control Of The Fully Submerged Hydrofoil Vessel

The fully submerged hydrofoil vessel(FSHV)is a new type of high-performance ship combining navigation technology and aerospace technique which possesses characteristics of high speed,outstanding sea-keeping performance,and all.When cruising at a high speed on the sea,the hull is elevated out of the sea by the lift which is generated by the hydrofoils installed under the vessel.Thus,the wetted surface area is reduced that the influence of the wave resistance and viscous force will be overcome and attenuated dramatically.Nevertheless,as the craft hull is totally above the sea,it cannot provide the restoring forces and moments under the wave disturbance that the stability and the safety of the FSHV cannot be guaranteed.Thus,a higher requirement is put forward for the motion control of the FSHV.At present,researchers of longitudinal motion control of the FSHV are mostly based on a linear model,without considering the influence of external disturbances.To improve the stability,a robust control strategy for the longitudinal motion control of the FSHV is proposed in this dissertation considering the difficulties and problems that still need to be solved.In view of the analysis of the dynamic of the longitudinal motion of the FSHV,a robust control strategy is designed to reduce the longitudinal motion of the FSHV and guarantee the global stability of the FSHV.The research of this dissertation proceeds from the following aspects:Firstly,the domestic and foreign research progress of the FSHV and the development of relative theories are summarized.The problem and demand for the controller design are illustrated according to the analysis of the structure and character of the FSHV.Then,according to the dynamic property of the FSHV,the structure of the closed-loop control system and the operating principle are proposed.The mechanism of the control system is described.Then,the nonlinear model of the longitudinal motion of the FSHV is established according to the theorem of the momentum of the rigid body.The hydrodynamic characteristic of the hydrofoil and the longitudinal motion characteristic of the FSHV under the ocean waves are analyzed.The disturbance forces of the FSHV under different wave conditions are simulated and lay a foundation for the study of longitudinal motion control.Secondly,in order to reduce the influence of the disturbance to the longitudinal motion of the FSHV and improve the robustness of the controller,a compound control system contains the disturbance observer and the modified adaptive complementary sliding mode controller is introduced.Firstly,according to the model of the multiple-input multiple-output system,a nonlinear disturbance observer is designed by introducing the auxiliary variable.The disturbance observer realizes the estimation of the disturbance of the system and reduces the conservatism.To restrain the influence of the disturbance,the generalized sliding surface and the complementary sliding surface are reconstructed by the estimation of the observer.Then,a compound controller which contains the nonlinear disturbance observer and the modified adaptive complementary sliding mode controller is designed by the adaptive law of controller gain and continuous hyperbolic tangent function.Thus,the chattering of the controller is attenuated.The coordinate of the disturbance rejection and the reduction of control error is realized.The robustness and the control precision of the longitudinal motion of the FSHV are improved.Then,to guarantee the stability and the control performance of the FSHV when the actuator is saturation,the author proposes an anti-windup adaptive global terminal sliding mode control for the longitudinal motion control of the FSHV.Considering the lumped uncertainties are difficult to obtain in advance,the radial basis function neural network is utilized for the estimation of the upper bound of the uncertainties.The weight of the network is adjusted by the gradient descent algorithm.Then,considering the actuator saturation situation,a nonlinear antiwindup compensator is designed according to the FSHV system.Then the adaptive global terminal sliding mode controller is designed according to the estimation of the uncertainties and actuator compensator.The influence of saturation is compensated through the feedback channel.The fast convergence of the states and the control performance of the system are guaranteed.The anti-windup control of the FSHV realized.Lastly,considering the length of the hydrofoil struts is limited,when the FSHV cruises at the high wave condition,the wave struck the hull of the FSHV and the foil of FSHV out of the wave have easily occurred.Then,the safety and the lifespan of the FSHV are influenced.Then,in order to control the longitudinal motion of the FSHV under the high wave condition,a wave height tracking control of the FSHV is proposed.The probability forecast models of the wave that struck the hull of the FSHV and the foil of FSHV out of the wave are proposed firstly according to the theorem of the threshold problem.The distribution test and Pearson's theorem were used to verify the model.Then,the wave height tracking control of the FSHV based on model predictive strategy is designed based on the model prediction algorithm.Considering the model uncertainties and the saturation of the actuator,the objective function is designed by the increment of the control to avoid the salutation of the controller.The relaxation factor is introduced to guarantee the optimal solution of each moment.The controller designed guarantees the wave struck the hull of the FSHV and the foil of FSHV out of the wave have not occurred.Meanwhile,the longitudinal motion of the FSHV and the energy consumption of the actuator are decreased.Thus,the wave height tracking control of the FSHV is effective.Lastly,considering the length of the hydrofoil struts is limited,when the FSHV cruises at the high wave condition,the wave struck the hull of the FSHV and the foil of FSHV out of the wave have easily occurred.Then,the safety and the lifespan of the FSHV are influenced.Then,in order to control the longitudinal motion of the FSHV under the high wave condition,the probability forecast models of the wave struck the hull of the FSHV and the foil of FSHV out of the wave are analyzed firstly according to the threshold problem and Pearson's theorem.Then the wave height tracking control of the FSHV based on model predictive strategy is designed considering the model uncertainties and the saturation of the actuator.The objective function is designed by the increment of the control to avoid the salutation of the controller and the relaxation factor is introduced to guarantee the optimal solution for each moment.The controller designed guarantees the wave struck the hull of the FSHV and the foil of FSHV out of the wave have not occurred.Meanwhile,the longitudinal motion of the FSHV and the energy consumption of the actuator are decreased.Thus,the wave height tracking control of the FSHV is effective.The research results of this dissertation possess the academic value and engineering application prospect.After further study,the research results can be applied to marine navigation,spacecraft,robots,and other relative aspects.