Sea-Skimming Tracking Control For High-Speed Aircrafts With Great Slenderness Ratio

High-speed aircrafts usually skim the sea at a low altitude to decrease detectability in long-distance flights.The marine disturbances cause strong impacts on tracking control of the aircrafts.Firstly,the waves cause the error between the actual altitude and the measured altitude.Secondly,the marine wind field causes the flow separation phenomenon that occurs on the sea-skimming high-speed aircrafts with great slenderness ratio.The unsteady aerodynamic effects also affect the controllability and tracking performance.Taking into account these factors,robustness is the main focus of the tracking control for sea-skimming aircrafts.Furthermore,to balance the robustness and time optimality,there is another matter of concern in the fixed-time convergence when sea-skimming aircrafts need to fly on the optimal trajectory in order to cut the flight short.This paper studies the robust longitudinal sea-skimming tracking control of high-speed aircrafts with great slenderness ratio.Considering the seaskimming aircrafts tracking control subject to the timing constraints,this paper also proposes an adaptive disturbance observer-based fixed-time convergent control method.The studies in this paper revolve around a cruise missile.The main contents of this paper are as follows.This paper first gives the longitudinal dynamic model and the aerodynamic model of the cruise missile.The mathematical models of waves,turbulence and wind filed are also presented to simulate the marine environment for the scenario studies.The tracking control of sea-skimming missiles subject to marine disturbances is addressed via higher order sliding mode control(HOSM)with adaptation.The adaptive super-twisting-like control in scalar case is utilized to compensate the external disturbances,aerodynamic uncertainties and sensor errors in different marine scenarios.The regulator composed of higher order sliding mode controller and differentiator achieves the finite-time convergence of the disturbance-free system.An adaptive disturbance observer-based fixed-time convergent control method is proposed for sea-skimming aircrafts to meet the timing constraints of optimal trajectory guidance.The adaptive tuning laws for fixed-time convergent super-twisting-like control in multivariable case are proposed to increase the speed of the system response,which is rarely studied in recent researches.The fixed-time convergence of the tracking control system is achieved via the feedback controller based on the implicit Lyapunov function control(ILF)method.