Optimization of helicopter and UAV coordinated SAR time.

The optimization of total helicopter-unmanned aerial vehicle (UAV) coordinated search-and-rescue (SAR) time to buy time for follow-up rescue activities is an important problem in air rescue that needs to be solved. In this study, helicopter was used as a carrier for the remote taking-off and landing (TAL) of UAV. The helicopter-UAV rescue time optimization, in which UAV is responsible for low-altitude detection task, include the remote TAL site selection model for UAV, the SAR task allocation model of UAV, and helicopter-UAV coordinated SAR time optimization model. To address the high site selection cost for the local TAL mode of UAV, a remote TAL site selection model for UAV in helicopter-UAV coordinated SAR was constructed in this study. Subsequently, a weighted distance matrix among SAR points was introduced, and an improved task allocation model of UAV was constructed to overcome security conflicts, which easily occur when UAV frequently runs across the helicopter airways. Finally, a helicopter-UAV coordinated SAR time optimization model of multi-UAV parallel searching was built to improve the coordinated SAR efficiency with considerations to the performance of the helicopter. According to the sensitivity analysis based on the earthquake of Yushu, the improved model increased the SAR efficiency significantly under different numbers of SAR points compared with the traditional mode. Specifically, the site selection cost under 50 SAR points was reduced by 56.08%, but the SAR efficiency was improved by 37.3%. This finding also demonstrates that the proposed method can adapt to SAR tasks in a larger scale. The proposed method provides references to study helicopter-UAV coordinated SAR problems.