Dynamic analysis and simulation of a split-torque transmission system under maneuver-induced load excitations

During helicopter maneuvering flight, the main rotor and tail rotor systems produce complex alternating dynamic loads. Under the combined excitation of external dynamic loads and internal structural excitations, the main gearbox presents obvious nonlinear dynamic responses. To explore the influence of maneuver-induced loads on the dynamic characteristics of the main gearbox, this paper proposes a modeling framework for analyzing the dynamic responses of the transmission system under diverse maneuver aerodynamic loads. The framework is established by integrating a coupled rotor–engine model with a lumped-parameter model of the transmission system. Based on the proposed framework, the vibration characteristics, load sharing performance, and dynamic load evolution of the transmission system under barrel roll and loop maneuvers are analyzed, where maneuver loads, time-varying mesh stiffness, gear backlash, as well as manufacturing and assembly errors are fully considered. The results show that load fluctuations and abrupt load variations occurring during barrel roll and loop maneuvers induce the torsional vibration responses of gear pairs to transition between quasi-periodic and chaotic states. Furthermore, the split-torque gear pairs show satisfactory load-sharing performance in the entry and recovery phases but degraded performance in the inverted flight phase, whereas an opposite trend is observed for the power-combining stage gear pairs. Nevertheless, the maximum dynamic load peaks appear in the entry and recovery phases, which degrades the operational stability of the transmission system. This study possesses important engineering application value, and the research findings provide a theoretical basis for the dynamic performance optimization of helicopter transmission systems.