Improved Twin Delayed Deep Deterministic Policy Gradient Algorithm Based Real-Time Trajectory Planning for Parafoil under Complicated Constraints

A parafoil delivery system has usually been used in the fields of military and civilian airdrop supply and aircraft recovery in recent years. However, since the altitude of the unpowered parafoil is monotonically decreasing, it is limited by the initial flight altitude. Thus, combining the multiple constraints, such as the ground obstacle avoidance and flight time, it puts forward a more stringent standard for the real-time performance of trajectory planning of the parafoil delivery system. Thus, to enhance the real-time performance, we propose a new parafoil trajectory planning method based on an improved twin delayed deep deterministic policy gradient. In this method, by pre-evaluating the value of the action, a scale of noise will be dynamically selected for improving the globality and randomness, especially for the actions with a low value. Furthermore, not like the traditional numerical computation algorithm, by building the planning model in advance, the deep reinforcement learning method does not recalculate the optimal flight trajectory of the system when the parafoil delivery system is launched at different initial positions. In this condition, the trajectory planning method of deep reinforcement learning has greatly improved in real-time performance. Finally, several groups of simulation data show that the trajectory planning theory in this paper is feasible and correct. Compared with the traditional twin delayed deep deterministic policy gradient and deep deterministic policy gradient, the landing accuracy and success rate of the proposed method are improved greatly.