Research On Safe Navigation Control Method For Hovercraft With State And Output Constraints

The hovercraft can sail on the surface of water-air at high speed,which has the advantages of speedability and amphibiousness.Therefore,the hovercraft can navigate in some special environments,such as shoals,swamps,snowfields,grasslands,etc.,which has the incomparable advantage with other displacement ships.However,the characteristics of cushioned navigation and special hull structure make the hovercraft more nonlinear and uncertain than ordinary surface ships.The research shows that the hydrodynamic and aerodynamic parameters of the hovercraft change greatly with the change of the navigation status,and the influence of the external environment make it have problems such as parameter uncertainty and inaccuracy of modeling.On the other hand,the hovercraft with underactuated characteristics lacks sufficient centripetal force and lateral force compared with the displacement ship.It is very easy to have dangerous situations such as stall phenomenon,high-speed tail-swinging phenomenon,drift during navigation.Therefore,given the safety problems in the navigation of hovercraft,it is of great significance and engineering application value to research the navigation control theory and method of the hovercraft.This paper takes the hovercraft as the research object and considering the problems of model uncertainty and external environmental disturbance,and the navigation risk of stall,high-speed tail-swinging caused by self-navigation characteristics,the state and output constraint control is carried out.The main research work is divided into the following aspects:(1)Aiming at the problems of the heading instability when the hovercraft sails at speeds near and below the resistance peak speed,an adaptive speed and heading control method are proposed for hovercraft with external disturbances based on an exponential disturbance observer.First of all,an exponentially convergent disturbance observer based on state tracking error is designed to compensate the external disturbance in the motion mathematical model of hovercraft.Secondly,considering the problem of the heading instability when the hovercraft sails below resistance peak speed and turning stall,a speed constraint controller based on ensuring the lower bound integral barrier Lyapunov function method is designed to keep that the navigation speed is above the resistance peak speed.Thirdly,in the framework of backstepping,a heading controller is designed to realize high-precision tracking of the set heading.Finally,the ultimately uniformly bounded stability of the speed and heading tracking system is proved in virtue of the Lyapunov stability theory,and the effectiveness and robustness of the proposed control strategy to external disturbances are verified by simulation experiments.(2)Aiming at the modeling error and to avoid the occurrence of dangerous navigation states such as stall and tail-swinging caused by the turning motion,a speed and turn rate constraint control method for hovercraft is proposed based on improved time-varying barrier Lyapunov function.Firstly,to avoid the phenomenon of tail-swinging during high-speed navigation,a turn rate constraint controller of the hovercraft based on improved tangent function barrier Lyapunov function is designed to achieve safe turning motion.Then,an exponential disturbance observer based on the state is designed to compensate the system uncertainty on the yaw degree of freedom.Furthermore,considering that the tangent function barrier Lyapunov function can only constrain the tracking error and can not constrain the state,two improved integral barrier Lyapunov functions are proposed for constraining the speed and turn rate of the hovercraft to avoid dangerous navigation situations.Then,according to the relationship between drift angle and surge and sway speed,the problem of transforming the constraint of drift angle into the speed constraint control is proposed,and the drift angle is also located in the constraint range by ensuring that the speed is always kept within the constraint range.Finally,the effectiveness of the proposed control strategy are verified by numerical simulation results.(3)Aiming at the trajectory tracking control problem of the hovercraft with the requirement of fast convergence of tracking error,a trajectory tracking control design method is proposed based on finite-time backstepping technology.Firstly,a finite-time observer is designed to quickly compensate the system uncertainties such as model uncertainty and external disturbances.Then,combining the nonlinear backstepping technology with the finite-time control theory,a finite-time trajectory tracking controller is proposed to track the virtual ship quickly and accurately.In order to further improve the robustness of the system and consider the influence of drift angle on control accuracy and navigation safety,a finite-time proportional integral sliding mode trajectory tracking control method with drift angle constraint is proposed.Firstly,a finite-time proportional integral sliding mode surface is proposed for the system tracking error to ensure the convergence of speed and turn rate tracking errors within finite time,so that position tracking errors can also converge to the origin within finite time.Then,a finite-time drift angle safety auxiliary adjustment system is designed and introduced into the turn rate control law.The turn rate control law is adjusted in real-time according to the size of the drift angle so that the drift angle can be kept in the safe region as much as possible.Finally,the effectiveness and fast convergence of the proposed finite-time trajectory tracking control method are verified by comparative simulation experiments.(4)Aiming at the trajectory tracking control problem of the hovercraft with the transient and steady-state performance of the position tracking error is constrained and speed and turn rate are required to be within the safe range,an appointed-time trajectory tracking control method is proposed based on performance envelope function.Firstly,a finite-time observer is designed to compensate for the compound disturbance of the trajectory tracking system,to improve the robustness of the system.Secondly,the position tracking error is controlled by using the new performance envelope function and the integral barrier Lyapunov function which directly deals with the tracking error,to ensure that the position tracking error is always kept within the predefined performance envelope curve.Thirdly,on the premise that the speed,drift angle and turn rate are in the safe region in the process of trajectory tracking control,the controller with the state constraint is designed to ensure the speed,drift angle and turn rate are always in the safe region.Finally,the effectiveness of the proposed trajectory tracking control strategy with the performance constraint of the position tracking error is verified by numerical simulation experiments.