Trajectory Design of High-Altitude Gliding Torpedo Based on Optimal Guidance Law

In the process of attacking submarines, the high-altitude gliding torpedo can increase the attack range by gliding extended range, and can attack outside the submarine defense area to effectively improve the survivability of carrier aircrafts. The air trajectory of the high-altitude gliding torpedo includes gliding extended range trajectory and parachute trajectory, and at the end of the gliding extended range trajectory, the torpedo will separate from its glider and open the parachute. As a result, the terminal trajectory constraint of the high-altitude gliding torpedo is more complicated than normal airdropped torpedo. To satisfy the terminal position and terminal trajectory inclination angle constraints, a trajectory model of high-altitude gliding torpedo is established based on the optimal control principle, and an optimal guidance law is proposed in this paper. According to the optimal guidance law and the overload control principle, the integral overload control method of the glider is given. The trajectory simulations between the traditional proportional navigation(PN) and the proposed optimal guidance law are compared. The results show that PN can satisfy the position constraint, which contains the horizontal control accuracy and the separation altitude of glider and torpedo, but exerts no control over the trajectory inclination, while the optimal guidance law can satisfy not only the constraints of horizontal control accuracy and separation altitude, but also the constraint of terminal trajectory inclination angle.