Dynamic Characteristics Analysis Of Planetary Gear Transmission Mechanism Of Space Manipulator

With the development of aerospace science and technology in China,space robotic arm,as the core equipment to cooperate with astronauts in space environment,is in urgent need of research.As the core part of space manipulator,the motion accuracy and stability of transmission joint have a significant influence on space operation.As an important part of the transmission joint,the motion stability of the planetary gear mechanism directly affects the working accuracy of the manipulator.Therefore,the planetary gear transmission system on a space manipulator is taken as the object to complete the three-dimensional modeling,dynamic modeling,numerical solution and dynamic characteristics analysis of the transmission mechanism.This article’s main research content is as follows:(1)On the basis of referring to relevant literatures at home and abroad,the research status and latest progress of the nonlinear dynamics of planetary gear transmission system were analyzed,and the achievements and shortcomings of the research of planetary gear transmission mechanism in space manipulator were summarized.According to the related parameters of the planetary gear transmission mechanism of space manipulator,the three-dimensional modeling of the overall transmission mechanism is carried out,which provides the basis for the modal analysis,and the total transmission ratio is calculated.(2)The four main factors of system transmission error,namely meshing stiffness,comprehensive meshing error,toothed clearance and meshing damping,were analyzed.On this basis,the nonlinear dynamics model of planetary gear transmission system was established by mass concentration method.The dynamic equations were solved by the Runge-Kutta numerical integration method with the 5th order variable step size,and the influence of different error factors on the dynamic response of the system was analyzed.Results show that when the tooth space increases,the increase amplitude of the gear,gear torsional vibration becomes more severe.When the meshing error increases,the system response bifurcates and periodically becomes chaotic.As the meshing error continues to increase,the range of system chaotic response also increases.When the excitation frequency increases,the system will experience a series of single cycle,periodic and chaotic motions of the change.(3)Based on the three-dimensional model,the finite element model of the transmission mechanism was established,and the modal simulation analysis was carried out.The first six modal shapes and natural frequencies of the transmission mechanism were studied,and the correctness of the theoretical model was verified by comparing with the calculated values of the theoretical model.The concept of modal energy is introduced,and based on the inherent characteristics of the system,the energy distribution of each order modal vibration of the system under different working conditions is analyzed.The modal energy ratio of the first four order vibration of the system under the starting,steady and emergency stop conditions was calculated respectively.The influence of different working conditions and clearance size on the variation trend of the system vibration was analyzed.Gear in the process of the steady state vibration,vibration mainly for low-order modal vibration.The research content of this paper lays a foundation for further research on the dynamic characteristics and structure optimization of planetary gear transmission system.