Safe Path Correction Method for Ambulance Aircraft Based on Low-Altitude Wind Prediction

The flight height of ambulance aircraft during aviation emergency rescue is low. Low-altitude wind fields and complex terrains may threaten the flight safety of rescue aircraft and thus limit rescue efficiency. The path planning of ambulance aircraft with consideration of low-altitude wind fields and terrains was presented in this study. First, a new wind field interpolation method was proposed to address the shortages of traditional reverse-distance wind field interpolation methods that neglect the effects of mountain slopes on wind vectors. This new interpolation method comprehensively considers the effects of terrain elevation, topographical slope, underlying surface roughness, and distance on wind vectors. The wind field interpolation results could accurately reflect the influence of topographic slopes on wind vectors and were close to practical results. Second, the effects of wind fields of different wind directions on flight paths were analyzed in view of the effects of low-altitude wind fields and restrictions of terrain obstacles. On the basis of the results, a method for correcting corresponding path nodes given aircraft performance constraints was proposed to ensure path safety. The connection matrix was solved by combining the A* algorithm and a 3D meshing technique. The safe path planning method for low-altitude rescue was concluded by combining a path-solving algorithm and the correction method for path nodes. Finally, the topographical features from Wenchuan and Chengdu to Mianyang during the Wenchuan earthquake were simulated with a constructed digital equation model. In the simulation environment, the safety of the path plan of the ambulance aircraft was verified under the influence of low-altitude wind fields.