This paper investigates the terminal guidance problem for the missile intercepting a maneuvering target with impact time constraint. An impact time guidance law based on finite time convergence control theory is developed regarding the target motion as an unknown disturbance. To further improve the performance of the guidance law, an autopilot dynamics which is considered as a first-order lag is taken into consideration. In the proposed method, the coefficients change with the relative distance between missile and target. This variable coefficient strategy ensures that the missile impacts the target at the desired time with little final miss distance. Then it is proved that states of the guidance system converge to sliding mode in finite time under the proposed guidance law. Numerical simulations are presented to demonstrate the effectiveness of the impact time guidance law with autopilot dynamics (ITGAD).
The paper proposes a new autopilot design for agile missiles flying at a high angle of attack (AoA). A maneuver strategy applicable to 90°AoA flight for agile turning is described prior to the missile modeling. Accounting for the disturbance rejection, the extended state observer (ESO) technique is employed for online estimation of the system uncertainties due to the aerodynamic unpredictability at high AoA regimes. Under the circumstances, linearization with dynamic compensation and non-singular terminal sliding mode control are applied to achieve controllability during 90°AoA flight. Numerical simulation results demonstrate the effectiveness and robustness of the proposed scheme. Additionally, the chattering caused by unmodeled dynamics is obviously mitigated with the action of the ESO.
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