A three-dimensional robust nonlinear guidance law in trajectory coordinates considering input dynamics and uncertainties

Viewing missile control system as a second-order reference model with uncertainties, this paper proposes a three-dimensional nonlinear guidance law in the trajectory coordinates based on small-gain theorem and input-to-state stability for interception of a maneuvering target. The guidance law designed in this paper, compared with most existing ones, is novel in that the acceleration in the trajectory coordinates is considered as the control variable directly, and the approach can compensate for the effects of the control loop dynamics and disturbances. The simulation results show that our scheme has strong robustness with respect to target maneuvers and bounded disturbances of control loop.