Optimal path planning for unmanned combat aerial vehicles to defeat radar tracking

The problem of path planning for unmanned combat aerial vehicles (UCAVs) in the presence of radar-guided surface-to-air missiles is treated. The problem is formulated in the framework of the interaction between three subsystems: the aircraft, the radar, and the missile. The main features of this integrated model are as follows. The aircraft radar cross section (RCS) depends explicitly on both the aspect and bank angles; hence, the RCS and aircraft dynamics are coupled. The probabilistic nature of radar tracking is accounted for, namely, the probability that the aircraft has been continuously tracked depends on the aircraft RCS and range. Finally, the requirement to maintain tracking before missile launch and during missile flyout are also modeled. Based on this model, the problem of UCAV path planning is formulated as a minimax optimal control problem, with the aircraft lateral acceleration serving as control. Necessary conditions of optimality for this minimax problem are derived and used as a basis for an efficient numerical solution. Illustrative examples are considered that confirm the standard flying tactics of "denying range, aspect, and aim," by yielding flight paths that weave to avoid long exposures of aspects with large RCS.