Research On Sliding Mode Decoupling Control Of Heave And Pitch Of Cushion Vehicle

The vertical plane control strategy of fully cushioned air cushion vehicle is an important means to ensure navigation safety.The main control method is to control the heave and pitch degrees of freedom by adjusting the air intake of the pad up fan.Therefore,in the vertical plane,it can be regarded as an underactuated strong coupling system with control input and two degrees of freedom.When the pitch angle is too large,the bow burying accident will occur;when the heave height changes greatly,it will affect the crew’s riding comfort.Based on the above problems,the air cushion model is firstly modeled and simulated.The gas in the air chamber is regarded as vertically compressible and horizontally consistent.Then the sliding mode decoupling controller is designed to control the heave height and pitch angle,and the control effect is compared with the single degree of freedom sliding mode controller.On the basis of the above research,In this paper,based on the above research,a disturbance observer is designed for the disturbance of the external sea waves,and the controller is designed by combining the disturbance observer with the sliding mode decoupling control law.Finally,the simulation results are compared with the simulation results without observer.The detailed research contents of this paper are as follows:1.The mathematical model of the air cushion system of the fully cushioned air cushion vehicle is established,and the gas density is correlated with the air chamber pressure.Through the simulation experiment,the average value of the balance pressure in the air chamber and the gas density are obtained.Then,based on the gas mass continuity equation and the moment balance equation,the mathematical models of the heave and trim degrees of freedom of the hovercraft are established and transformed into the state space form.In this modeling method,the air intake of the pad up fan is taken as the control input,and the state variables are heave height,heave speed,pitch angle and pitch velocity.Based on Arduino control board,the ship model is made,and the heave height,trim angle and corresponding acceleration in the ship model experiment are obtained by carrying a ten axis sensor,which verifies the coupling between the heave and trim degrees of freedom of the hovercraft under a single control input.Finally,simulation experiments are carried out on the model with different air intake,which proves that the established mathematical model is in line with the actual motion situation,which lays a foundation for the design of the controller in the following chapters.2.The heave pitch coupling model is established,and the sliding mode controller is designed to control the heave and pitch degrees of freedom,and then the sliding mode decoupling controller with two degrees of freedom is designed for simulation verification.Then,the basic principle of sliding mode control method,the existing problems and the method of sliding mode chattering suppression are introduced.It is verified that the decoupled sliding mode control has the advantages of shorter adjustment time and less jitter than the single degree of freedom sliding mode control when there is coupling effect.It is verified that the designed sliding mode decoupling controller can effectively control the heave height and pitch angle.3.In the three marine environments of wind,wave and current,The vertical motion of the hovercraft is mainly disturbed by waves.Therefore,this paper mainly considers the interference of external waves on hovercraft.Firstly,the wave disturbance equation is established based on P-M wave spectrum.Because the wave disturbance is the superposition of a series of sine functions,the disturbance must be bounded.A sliding mode decoupling controller is designed based on the ocean wave disturbance observer to control the heave height and pitch angle.Finally,the simulation results show that the decoupled sliding mode controller with disturbance observer designed in this chapter can effectively compensate the wave disturbance and reduce the amplitude of heave height and pitch angle.