variable structure finite time guidance law with autopilot lag

in this paper, the problem of finite time stabilization for guidance system is investigated and a novel nonlinear guidance law against maneuvering targets is proposed based on the principles of parallel navigation. the proposed law is developed using two variable structure control techniques. by applying finite time integral sliding mode and combining it with terminal sliding mode, a new guidance law with finite time convergence is designed. it is demonstrated that the proposed law is able to drive the line-of-sight (los) angular rate to the origin in finite time, before the final time of guidance process. due to their crucial importance, the autopilot dynamics are taken into account and finite time stability of the guidance system is guaranteed in spite of the autopilot dynamics. furthermore, in practice, it is desirable that the target acceleration be regarded as an unknown bounded disturbance. since the proposed law is robust against target maneuvers, the exact measurement or estimation of the target acceleration is not required. three-dimensional simulation results verify the robustness and usefulness of the proposed technique.