Aerodynamic Parameter Identification And Integrated Autopilot-guidance For Guided Projectiles

Indirect-fire artillery weapon systems on the battlefield responsive,able to provide strong and sustained fire support,are important elements of future joint operation troops.With the development of modern war concepts,remote suppression,precision strike and efficient damage,etc.have become the focus of the development of intelligent ammunition The guidance and control system of a guided projectile is the key to its precise strike.By the launch platform restrictions,the ability to control the guided projectiles is limited.The integrated design of guidance and control can take full account of the coupling relationship between the guidance and the control systems to ensure the stability of the cascade systems as a whole,so as to fully exploit the potential of guided projectiles and improve hitting accuracy.Good guidance and control systems are designed depending on reliable dynamic models and parameters.Therefore,in this dissertation.two aspects of the key technologies for guided projectile are investigated:one in the field of dynamics modeling is using flight test data to identify aerodynamic parameters,and the other in the field of guidance and control design is integrated guidance and control synthesis.Firstly,several different forms of six-degree-of-freedom rigid-body dynamics models for guided projectiles are presented,and the aerodynamic characteristics of guided projectiles is studied from the view of control.A "rigid-body-particle" model is established for integrated guidance and control design,with the guided projectile described by six-degree-of-freedom rigid body dynamics and the target assumed to be a controllable particle.The model reflects not only the relative motion relationship between the guided projectile and the target but also the attitude of the guided projectile during the terminal guidance phase.Then,the problem of using flight test data to identify aerodynamic parameters is studied.The parameter identification problem is casted into a state estimation problem by extending the drag coefficient for identification to the system states,and an improved form of hybrid extended Kalman filter(HEKF)is proposed.In order to avoid the divergence or even instability in the implementation of HEKF caused by modeling errors and finite precision of digital microprocessors onboard the projectiles,fictitious process noise is added to the system model and covariance matrix is symmetrized at each time step.As a result,the robustness of HEKF is improved.A maximum likelihood identification method based on the artificial fish swarm algorithm is proposed for identifying the longitudinal aerodynamic parameters for guided projectiles using the flight test data,overcoming the problem of initial value sensitive of Newton-Raphson's optimization in the traditional maximum likelihood estimation method.The experiment design plays a important role in the parameter identification.For latal aerodynamic parameter estimation for guided projectile,the influence of different inputs and different signal-to-noise ratios(SNR)on the accuarcy of aerodynamic parameter identification is studied for applying recursive Fourier transform regression.The SNR range corresponding to different identification accuracy is given.Then,the integrated guidance and control design for guided projectiles is studied from the view of the optimal control.The structures of classical three-loop autopilot,proportional guidance law and several common guidance laws are explained from the perspective of the optimal control.Two kinds of the integrated guidance and control design based on the linear quadratic regulation(LQR)are proposed for canard-controlled guided projectiles to intercept head-on maneuvering targets with constant normal acceleration.The simulation results show that the single-loop integrated guidance and control and the two-loop integrated guidance and control law based on the LQR can make the miss distance converge to zero at the end of interception.There is no problem of acceleration divergence while the projectile is approaching the target.Two kinds of integrated guidance and control design based on the finite-horizon state dependent Riccati equations(Finte-SDRE)method are proposed for tail-controlled guided projectiles to intercept head-on weaving targets.The simulation results show that the miss distance converges to zero at the end of interception using either the single-loop integrated guidance and control or the two-loop integrated guidance and control law,and that the acceleration profiles of the integrated guidance and control laws are better than that of the separated guidance and control.Finally,the integrated guidance and control design for guided projectiles is studied from the view of the robust control.An integrated guidance and control law based on quasi-continuous second-order sliding mode control is proposed for guided projectiles to intercept maneuvering targets,considering the aerodynamic parameter uncertainties of guided projectiles and unknown bounded target maneuvering strategies.By Lyapunov stability theory,it is proved that the proposed method can converge and keep the angular rate of the line-of-sight to zero in the finite time.A robust two-loop integrated guidance and control law based on the high-order sliding mode observers is proposed and its effectiveness is proved using Lyapunov stability theory,for guided projectiles to intercept maneuvering targets,considering measurement limitations,the uncertainties of guided projectile aerodynamic parameters and unknown bounded maneuvering strategies.The simulation results show that the proposed integrated guidance and control law possesses high hitting accuracy and good acceleration characteristics.A novel robust impact-angle-constrained guidance law with autopilot-lag is proposed based on integral sliding mode and dynamic surface control for guided projectiles.The stability of the line-of-sight rate and the line-of-sight angle bias is proved in the sense of the uniform boundedness and ultimate boundedness via Lyapunov stability theory.The simulation results show that the proposed method can make the guided projectile hit the target with high accuracy at a given impact angle in the presence of target maneuvering uncertainty and autopilot disturbance,and that the acceleration characteristics is good.