In order to achieve a straight ballistic trajectory of missile and reduce the update frequency of the missile normal acceleration for the interception of maneuvering target, a backstepping-based parallel approaching guidance method is designed with nonlinear disturbance observer (NDO) technique and event-triggered (ET) mechanism in this paper. In order to suppress the adverse effect of target maneuver, the NDO is designed to estimate the target maneuvering acceleration. Then, the NDO-based backstepping method is used to obtain the normal acceleration of missile and realize the parallel approaching guidance. In order to reduce the update frequency of missile normal acceleration, the ET mechanism is employed in the parallel approaching guidance method. If the missile trajectory is relatively straight, the normal acceleration of missile remains unchanged. On the contrary, if the missile trajectory is not straight, the normal acceleration of missile is updated to make the missile trajectory straight. In this way, the ET-based parallel approaching guidance can be obtained. Furthermore, a determined method for the initial missile flight-path angle is proposed to keep the normal acceleration of missile at zero in the initial stage of interception. Besides, Lyapunov stability analysis method is used to prove that all signals in the closed-loop guidance system are uniformly ultimately bounded. Finally, simulation results show the effectiveness of the proposed guidance method.

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