Reliability modeling and analysis of unmanned aerial vehicle parachute systems considering falling dynamics and failure causality

Unmanned aerial vehicles (UAVs) are playing an increasingly important role in modern society, presenting significant safety challenges. As the ultimate line of defense for safety, the reliability of UAV parachute systems is crucial. This paper proposes a novel dynamic reliability model for UAV parachute systems that incorporates falling dynamics and failure causality by revealing the coupling evolution mechanism of discrete events and continuous changes of the UAV parachute system. First, through a comprehensive analysis of the physical operating process of the parachute system, a six-stage dynamic model is developed to describe the full deployment sequence. Based on this model, a failure-causality logic is constructed, accounting for both material degradation and pyrotechnic impulse loading effects. Furthermore, a stochastic hybrid automaton (SHA) combined with the event tree analysis (ETA) is put forward to describe the system reliability, and a simulation-based algorithm is also developed for reliability analysis. Finally, a case study is conducted to demonstrate the effectiveness of the proposed models, and the influences of UAV parameters, environmental factors, and uncertainties are evaluated accordingly.