Three-dimensional nonlinear coupling guidance for hypersonic vehicle in dive phase

Abstract

Three-dimensional (3D) nonlinear diving guidance strategy considering the coupling between longitudinal and lateral motions for hypersonic vehicle is investigated in this paper. It constructs the complete nonlinear coupling motion equation without any approximations based on diving relative motion relationship directly, and converts it into linear state space equation with the same relative degree by feedback linearization. With the linear equation, slide mode control with strong robustness is employed to design the guidance law, and 3D diving guidance law which can satisfy terminal impact point and falling angle constraints with high precision is obtained by substituting the previous control law into the origin nonlinear guidance system. Besides, regarding lateral overload as the standard, hybrid control strategy which can take full advantage of the excellent characters of both bank-to-turn (BTT) and skid-to-turn (STT) controls is designed to improve the guidance accuracy further. Finally, the results of CAV-H vehicle guidance test show that the algorithm can realize high accuracy guidance even if serious motion coupling exists, and has strong robustness to the path disturbances and navigation errors as well.