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A dynamics model of herringbone planet train with double teeth coupling is established based on the vibration theory of the concentrated parameter. The mesh stiffness formula of the helical gear is introduced to calculate the time-varying mesh stiffness of the herringbone teeth in the way of stiffness parallel of two helical gears. The relationship curves between the mesh stiffness of the internal and external meshes and the dynamic load coefficients of the internal and external meshes are obtained by solving the dynamic equation, and the impact of the mesh stiffness of the internal and external meshes on the dynamics load characteristics of the train is analyzed. The research results show that the dynamic load coefficients of the internal and external meshes increase with the average components of the mesh stiffness of internal and external meshes without regard to the resonance, respectively. The impact of the alternate component of the mesh stiffness of the internal and external meshes on the dynamic load coefficients is much less. Because of smooth operation and small vibration of the herringbone tooth, it is feasible that the average component of the mesh stiffness represents the mesh stiffness for the calculation of dynamic load coefficient of herringbone planetary train, when the required accuracy is not too high. [ABSTRACT FROM AUTHOR]

According to the actual load suffered by a servo mechanism in a large launch vehicle, a comprehensive load simulation system was presented, which could simulate the inertia, elastic, friction and constant loads. The inertia load, elastic load and flexible assembling base of servo mechanism were simulated by the mechanical structures, and the friction load and constant load were simulated using a hydraulic system. A complete mathematical model was constructed by modeling the servo mechanism, its flexible structure and the loading hydraulic system. It is shown that this system can reproduce the load characteristics of the servo mechanism in actual situation, and the redundant force of the loading system is suppressed effectively. A load simulation system was developed for simulation of the loads and resonant characteristics, which provides the necessary fundamental facilities for ground test and further research of servo mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: Under-voltage load shedding is an important measure for maintaining voltage stability.Aiming at the optimal load shedding problem considering the load characteristics,firstly,the traditional under-voltage load shedding scheme based on a static load model may cause the analysis inaccurate is pointed out on the equivalent Thevenin circuit.Then,the dynamic voltage stability margin indicator is derived through local measurement.The derived indicator can reflect the voltage change of the key area in a myopia linear way.Dimensions of the optimal problem will be greatly simplified using this indicator.In the end,mathematical model of the centralized load shedding scheme is built with the indicator considering load characteristics.HSPPSO is introduced to slove the optimal problem.Simulation results on IEEE-39 system show that the proposed scheme display a good adaptability in solving the under-voltage load shedding considering dynamic load characteristics. [Copyright &y& Elsevier]