Double-body Yaw Motion Control Method Of Wave Glider

An unmanned wave glider(UWG)composed of floating body(Float),submerged body(Glider)and umbilical cable(Umbilical)is a multi-functional marine environment monitoring and data transfer platform,which has the ability of full autonomy,unlimited endurance and adaptability to extreme environment.The unique double-body structure of UWGs is different from the traditional ocean vehicle.Due to its practical value in marine biological survey,meteorological data monitoring,marine acoustic monitoring and positioning,related technologies have developed rapidly in recent years.In the field of UWGs motion control,the research on model-based and model-free yaw control has been carried out.Considering the disadvantages of model free control,such as large calculation load,unstable control and uncertain parameters,model control is preferred as the yaw motion control method of UWGs.However,the current mathematical models of UWGs involve the estimation of hydrodynamic parameters and the calculation of a large number of inertia parameters,which is difficult to meet the requirements of the yaw motion control.For this reason,this paper establishes a double-body coupled yaw motion maneuverability response model to solve the problems of mismatching control model and insufficient precision;based on this model,a double-body variable-structure yaw motion filtering method considering the relaxation / tension of Umbilical is proposed to solve the high frequency chattering problem and the filtering problem of Umbilical state switching;an improved indirect control method for the yaw motion of Float is proposed which improves the effect of orientation control and tracking control.The main contents of this paper are as follows:First of all,according to the characteristics of the UWG's double-body yaw motion,and on the basis of reasonable assumptions,the coupling relationship between the two body's yaw motion is analyzed,and the maneuverability response model of the coupled double-body yaw motion considering the lag of the Umbilical is established.For the UWGs equipped with a single yaw motion sensor on Float,the identification method of Umbilical lag time based on the least square method and Fibonacci method is designed.By the synchronous characteristics of the double-body yaw motion,the step-by-step identification method are designed to identify six yaw maneuverability parameters based on a set of Z-shaped test data and rotation test data.The numerical simulation results of the phase difference of heading angle between the two bodies verify the linear identification conditions.By comparing the simulation and tank test results of the model with and without considering the hysteresis of Umbilical,the generalization of the former is better than that of the latter.At the same time,it is shown that the lag time of Umbilical is an indispensable parameter in the identification model,and the importance of considering the lag time of Umbilical is shown.It provides a maneuverability response model for the research of filtering and control of the UWG's double-body yaw motion.Then,by using the double-body coupled yaw motion maneuverability response model considering the lag of the Umbilical,an iterative-mean EKF method is proposed to smooth the sensor data accurately and effectively.In order to solve the problem of unconstrained motion of the double body caused by the relaxed state of the Umbilical under high sea conditions,a criterion for determining the variable structure of the dual body yaw system is proposed,which realizes the correct matching of the filtering models of the free state and the constrained state.Based on the iterative-mean EKF method and the variable-structure criterion of the double-body yaw system,a variable-structure yaw motion filtering method considering the relaxation / tension of the Umbilical is proposed.The filtering method combined with the estimation of the model of the yawing motion of the two bodies is used to obtain the smooth data of the yaw motion of the two bodies under the condition of the whole sea state,which provides a stable control input for the control system of the double-body yaw motion.Then,in view of the particularity of the double-body structure and energy drive of the UWGs,the problems existing in the control system of the double-body yaw motion are analyzed,and the importance of the Umbilical lag time is expounded.In order to solve the problem that the lag time of Umbilical is shifted due to the attachment of marine organisms,a pulse steering identification method is proposed,which is suitable for on-line identification of long-distance navigation.In order to solve the problem of mismatching control expectation and control feedback at the same time in control system,a control strategy of double-body yaw motion considering the lag time of Umbilical is proposed to coordinate the consistency of control expectation and control feedback.The feasibility of the control strategy is verified by simulation experiments.At the same time,based on the control strategy of the double-body yaw motion considering the lag time of the Umbilical,the control method of the double-body yaw motion is studied,which comprehensively improves the stability and rapidity of the control system.By simplifying the double-body coupled yaw motion maneuverability response model,the response model of the yaw motion of the Float is obtained.Based on the model,the direct control method of the yaw motion of the Float is proposed.Aiming at the disadvantage that the direct control method of the yaw motion of the Float is difficult to overcome the inertia of the system,an indirect control method for the yaw motion of the Float is proposed based on the double-body coupled yaw motion maneuverability response model,in which the yaw motion control method of the Glider is attached.In the indirect control method,four kinds of combination modes of the controller are compared,and the optimal combination mode of the linear controller for the Float and the fast controller for the Glider is determined.In order to solve the problem of high frequency chattering near the target,two improved methods are proposed: the stress indirect control method and the degenerative indirect control method of the yaw motion of the Float.Compared with the numerical simulation results,it is shown that the two improved methods are suitable for directional control,and the latter is more suitable for tracking control than the former.Adjusting the approach attractor in the degenerative indirect control method based on energy level,the energy-saving control method of the yaw motion is proposed;according to the phase difference of the heading angle of the two bodies,the control method of the stability of the double-body structure is proposed.the degenerative indirect control method is integrated with energy saving and stability function of double-body structure.The problems existing in the control system are solved comprehensively.Finally,the system structure of the UWGs is built,and the prototype is established.The design method of the energy system is emphasized,which provides the energy level parameters for the energy-saving control method.The rationality,reliability and safety of the structure design of the prototype are verified by tank and sea experiments,and the ability of motion control and environmental monitoring of the prototype is proved.