Impact time control guidance law with time-varying velocity based on deep reinforcement learning

This paper investigates the problem of impact-time-control guidance law with the time-varying velocity caused by gravity and aerodynamic drag. Using the deep reinforcement learning (DRL) algorithm, we propose a novel impact time control guidance (ITCG) law in which a DRL agent is trained from scratch without using any prior knowledge. Different from the traditional ITCG law, the proposed method doesn't rely on the time-to-go estimation, which is difficult to derive and inaccurate with the time-varying velocity. Further, a prioritized experience replay method and a novel action exploration method are introduced in the DRL algorithm to improve learning efficiency. Additionally, the agent action is shaped to provide smooth guidance command, which avoids the problem that the guidance command generated by the intelligent algorithm may not be continuous. Numerical simulations are conducted to support the validity of the proposed algorithm.