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The optimization design of the face gear split-torque transmission (FGST) consumes a lot of modeling and calculation costs. Implementing closed-loop design for data generation optimization improves system design efficiency. However, there are two challenges: firstly, the lack of a mapping method for the tooth surface modification parameters to discrete mesh coordinates, which makes it difficult to generate data samples; secondly, a quantitative representation method for evaluating contact performance has not been proposed, making it difficult to achieve quantitative design. In this paper, we propose a fast integration method of analysis and optimization to the contact performance design of a face gear split-torque transmission. An efficient mapping method from FGST geometric parameters to discrete grids is established to achieve fast data generation. A quantitative evaluation method for contact performance based on image processing has been proposed to achieve rapid optimization. The time required for modeling and optimization is shortened to less than 0.5 h, significantly improving design efficiency.

Concentric face gear split-torque transmission system (CFGSTTS) has great applied value in the field of aeronautical transmission due to the characteristic of high integration. Mesh stiffness, as one of the most primary sources of vibration, is vitally important for the dynamic performances of gear transmission system. The existing finite element method (FEM) and analytical method (AM) are not suitable for tackling the mesh stiffness calculation of closed-loop multi-branch system such as CFGSTTS. Thus, a semi-analytical method (SAM) is presented and verified, which combines the high precision of FEM with the high efficiency of AM. Additionally, the differences between the mesh stiffness of independent face gear drive and that of the same gear pair in CFGSTTS under accordant load is researched by applying SAM. The influence rules of distribution angle and load condition on the mesh stiffness of gear pairs considering system structure are also studied. Results demonstrate that the mesh stiffness of gear pairs in CFGSTTS is time-varying and tends to be consistent with each other by adjusting load parameters.

A calculative model for parallel shaft split torque transmission system is presented, the model includes stiffness of shaft supporting, time-varying stiffness, damping, gear eccentric error errors, bearing eccentric errors, gear tooth thickness error, assembly error. Dynamic analytic model is built using the theory of equivalent mesh error and Newton method. The model was solved by variable step size forth/fifth-order Runge-Kutta method. The result shown all error affect load sharing in different way, one error deduced sharply can not improve load sharing obviously.

The helicopter power transmission system technology is the key technical area for improving the helicopter performance, reducing the noise/vibration level of helicopters and decreasing the cost of life cycle of helicopters. In this paper, the technical characteristics of the helicopter power transmission system are introduced first. Then, the development history and trend of the transmission configuration, the component and the design and analysis technique of the transmission system are described. The advanced material and process technology applied in the helicopter power transmission system are also described. Finally, the power transmission system technology used in the high speed helicopters is briefly presented.

A helicopter transmission with split-torque drive trains to the main rotor and tail rotor drive shaft is described. A design based on two 1200 kW engines supplying torque to a 350 r/min main shaft demonstrates a weight reduction of 40 per cent, extreme low height and reduced losses. Four double-helical pinions drive a combining gear and provide a 10:1 reduction ratio to the main shaft; flexible torque tubes, set by fine-difference splines, control the division of torque between pairs of pinions. Rotor loads bypass the transmission housings and pass to the fuselage through a large-diameter mast that encloses an integral sump and cooler.