Optimal Closed-loop Guidance For Cruise Missiles Based On Pseudospectral Method

Cruise missiles facing complex constraints are prone to deviate from the intended trajectory due to disturbances and unexpected situations in flight,which and more new functions are needed to achieve more real-time and adaptable trajectory optimization and guidance methods.This dissertation is about the flight trajectory optimization and optimal closed-loop guidance problem of subsonic cruise missiles based on pseudospectral method.Firstly,according to the development status of trajectory optimization,the main ideas and methods of solving optimal control problem are expounded.The indirect method and the direct method are also compared in principles and characteristics.It is shown that the optimal control problem of trajectory optimization is solved with pseudospectral method efficiently and accurately.Secondly,the mathematical description and simulation model of cruise missiles trajectory optimization problem is established by missile dynamics modeling,motion modeling and battlefield environment modeling,etc.It provides the solution to the problem and the realization of optimal closed-loop guidance.Thirdly,the trajectory optimization problem is transformed into the continuous optimal control problem with the differential equation of missile motion as the state equation.According to the pseudospectral method,the continuous optimal control problem continues to be approximated as a finite-dimensional nonlinear programming problem subject to a large number of algebraic equality constraints and inequality constraints.The effective nonlinear programming method is used to solve the problem,and the flight trajectory of the maximum missile survivability probability satisfying the battlefield environment constraints is obtained.And the simulation experiment of the Tomahawk cruise missile is carried out to verify the equivalence of the pseudospectral method and the feasibility of the flight trajectory.Finally,based on solving the optimal control problem of trajectory optimization with pseudospectral method,the optimal closed-loop guidance is realized by continuous on-line trajectory reconstruction using the rolling time-domain strategy.Two specific methods of fixed and free updating period of guidance law are discussed,and their characteristics are studied.The simulation experiments are also undertaken for the unexpected events and disturbances that may be encountered during flight,which verify the capability and feasibility of this method.The optimal closed-loop guidance for cruise missile based on pseudospectral method can meet the requirements of real-time and accuracy,and has good adaptability to different interference errors and task modification forms.This method is valuable to our cruise missile mission planning and to ensure mission completion in the complex battlefield environment.