Dynamic Analysis And Control Methods For Wave Glider

Unmanned wave gliders(UWGs)are a new type of wave-powered unmanned marine vehicle.The thrust of a UWG comes from wave energy.The electronic power of the control system is provided by solar panels.UWGs overcome the constraints of limited energy for conventional marine vehicles and realize powerful endurance through innovative energy utilization.In recent years,UWGs have been widely applied to multifarious fields like marine environmental monitoring and marine data relay.However,the unique rigid-flxible multi-joint structure brings huge difficulties to the dynamic analysis and control algorithm researches for UWGs.The following problems were discussed:the dynamic modeling problem of UWG,the adaptive filtering method for the multi-body yawing motions of UWG,the course control problem of UWG,and the heading control problem of the surface float body(float)Firstly,the dynamic model of a UWG with flexible umbilical was established considering the influences of the flexibility of the umbilical on the dynamic characteristics of UWG.The dynamic models of surface float body(float)and submerged glider(glider)with slack umbilical were firstly separately established,and subsequently,the dynamic model of the UWG was formulated when the umbilical was under tension.Furthermore,the judgment principle and the state transfer problem in the switching process were analyzed.The dynamic model of a UWG when the umbilical was under tension was formulated through the decomposition,conversion and synthesis of forces and motions of the dynamic models of the float and the glider with slack umbilical.The established dynamic model of a UWG with flexible umbilical was found to be reasonable to reflect the dynamic characteristics of UWG by the numerical simulation and tank test results.The relative amount of time the umbilical spends slack is considerable,and it is with great significance to consider the influences of the flexibility of the umbilical on the dynamic characteristics of UWG.Then,an adaptive filtering method for the multi-body yawing motions of UWG was proposed for the estimation of the headings and yawing velocities of the float and the glider Considering the multi-body yawing driving principle of UWG,the linear response models of the yawing motions of the float and the glider were respectively established,and the dynamic response coefficients of the yawing motions of the float and the glider were adaptively revised by the dynamic data in the actual sailing of UWG.On this basis,the adaptive filtering method for multi-body yawing motions of UWG was proposed based on the frame of the extended kalman filter(EKF)method.The proposed adaptive filtering method for multi-body yawing motions of UWG leverages the information of the input and output data in the estimation process,and is independent of the mechanism mathematical model of UWG.The numerical simulation results prove that the proposed adaptive filtering method suppresses the noise effectively even with model parameter perturbation,and the tracking performance is satisfied.Next,aiming at the course control problem of UWG,the course control method with multi-body heading information fusion was proposed.The rudder is equipped on the glider and drives the glider to turn directly.The tension of umbilical drives the float to turn indirectly.The course of UWG is influenced by the heading of the float,the heading of the glider and environmental interference factors.The heading of the float,the heading of the glider and system course of UWG are correlated,but not equal at most of the time.The course control problem of UWG is a special kind of weak maneuvering control problem.The multi-heading dynamic coupled model of UWG and the estimation method of the offset radio coefficient(ORC)were proposed to describe the real-time interrelation of the heading of the float,the heading of the glider and system course.The multi-heading information fusion strategy was proposed to calculate the desired heading of the glider.Via direct heading control of the glider,the course control of UWG was realized indirectly.Simulation and sea trial results demonstrate that the proposed multi-heading dynamic coupled model of UWG and the course control method with multi-body heading information fusion improve the course control performance of UWG significantly.Next,aiming at the difficulties of the time-delay heading control problem of the float,the adaptive heading control method for the float was proposed.There is a large time lag of the heading response of the float,and the heading control of the float cannot be duplicated by the heading control of the glider.It is hard to stabilize the heading control system of the float by conventional control methods.The basic and improved arrangement methods of the desired heading of the glider were proposed.The compensation of the desired heading of the glider was realtime modified by the actual sailing data.The time-delay heading control problem of the float was converted to the heading control problem of the glider which was relatively easy.Simulation and sea trial results demonstrate that the proposed adaptive heading control method of the float improves the heading control performance of the float significantly,and is practical in the actual applicationsFinally,the sea trials of the UWG were introduced,including the structural design of UWG,the architecture of the control system,the installation,release and recovery of the UWG.Part of the sea trial results,including the heading control experiment of glider,the waypoint following experiments,the autonomous marine environmental monitoring experiments,and the autonomous long voyage test were demonstrated to verify the reliability and the motion control and environmental monitoring performances of UWG in actual sailing.