Research On Guidance Method Of Aircraft Based On Adaptive Sliding Mode Tracking And Polynomial Prediction

Lifting body configuration has been adopted by many advanced hypersonic vehicles,because of several advantages such as: lift-to-drag ratio is large,maneuver capacity is powerful,internal space is utilized efficiently and aerodynamic characteristics are excellent under hypersonic flying environment.In this dissertation,reentry trajectory optimization and guidance of hypersonic lifting vehicles are studied.The detailed research work includes the following aspects:A reentry fast trajectory optimization method based on particle swarm optimization and Gauss pseudo-spectral method is studied and introduced.Firstly,an angle of attack velocity profile suitable for reentry section is designed,and a heeling angle velocity profile conforming to the constraints of reentry process is also designed in combination with the flight reentry corridor.Then,the particle swarm optimization algorithm is used to optimize the characteristic node values in the control profile under the condition of ensuring the rapidity to obtain the suboptimal trajectory.Using the high precision transcription characteristics of Gauss pseudo-spectral method,combined with the obtained suboptimal trajectory as the initial guess solution of Gauss pseudo-spectral method,the optimal trajectory with higher precision,better effect and better constraint satisfaction is obtained.Finally,the algorithm is verified by experiments,and the results show that the algorithm has strong robustness and high precision,which provides the nominal trajectory for the reentry tracking guidance.An adaptive sliding mode tracking guidance method based on quadratic linear regulator is studied and introduced.Firstly,the longitudinal nonlinear motion equation of the reentry vehicle with fast time-varying characteristics is transformed into a typical second-order nonlinear system equation by linearizing each moment equilibrium point of the nominal trajectory with small deviation.Then,the sliding mode guidance method with integral switching function is designed,and the adaptive guidance term is added into the guidance rate.At the same time,feedback gain is designed based on the linear quadratic regulator,which has a good effect on correcting the errors generated by the linearized tracking guidance method,and the robustness of the control method is enhanced.Finally,the simulation results show the effectiveness and robustness of the guidance scheme under large aerodynamic deviations.A predictive guidance method based on polynomial method is studied in this paper.It firstly introduces a method for estimating aerodynamic coefficient deviation from body shafting acceleration and aerodynamic model provided by aircraft sensor.Aiming at the reentry stage of the lift-type aircraft,the flight trajectory from descending to pulling up is designed,and the approximate formula of range,speed and level flight height is deduced to calculate the level flight altitude.Then,a polynomial method is adopted to plan the trajectory from the current flight altitude to the level flight altitude.Through transverse and longitudinal lift acceleration,the control quantity is derived in reverse.Finally,the simulation results of Monte Carlo shooting method under nominal state verify the performance of this method under large deviation.