| With the important national demand of China's space technology,the application of the aerospace institutions such as space station large-scale robotic arm and satellite antenna is becoming more and more extensive,and the complexity of performing space tasks as well as the accuracy requirement of the stability and reliability of such institutions is increasing.As the core part of them,the transmission joint mainly completes the mechanical connection,power transmission and other works,and has a direct impact on the position accuracy of the space robotic arm and the satellite antenna pointing accuracy.In this paper,in response to the multi-gap phenomenon and rigid-flexible coupling phenomenon in the planetary gear train system,a variety of dynamic models are established and numerical simulation is performed.The main research work is as follows:Firstly,the significance and related backgrounds of the research are expounded,the development status,advantages and disadvantages of the related research are analyzed,and the research direction and key points of this paper are put forward.The study of the dynamics of the aerospace mechanism will help to improve the design and analysis level of the aerospace institutions,delay the wear of the aerospace institutions,prolong the service life,and provide reference for the development of other large-scale institutions.Secondly,as the helical gear is widely used as transmission part in the planetary gear train system,a six-degree-of-freedom bending-torsion-axis coupling dynamic model is established for the helical gear.Considering the tooth side clearance,time varying meshing stiffness and meshing damping in the helical gear transmission,the gear meshing stiffness and the gap function equation are deduced.In order to analyze the influence of the tooth profile modification on the gear meshing transmission,the tooth profile modification model is established,and the modification curve equation is analyzed by different curves.The results are substituted into the dynamic model of the original helical gear transmission,and a five-degree-of-freedom dynamic equation systematically considering tooth profile modification is obtained.The numerical simulation results show that the external stimulation,the tooth side gap and other factors have great influence on the vibration of the gear transmission,and the reasonable tooth profile curve can effectively reduce the system amplitude.Thirdly,a planetary gear train joint with multiple sets of helical gears is analyzed,and the dynamic models of the planetary gear transmission system and the flexible arm considering multi-gap factors are established.The Lagrangian multiplier method is used to establish the systematical dynamic equations involving the planetary gear train joint and the flexible arm.In the numerical simulation,through the comparison of the multi-gap model and the rigid-flexible coupling model,it is found that the coupling of the flexible arm and the multi-gap inside the joint causes the vibration of the transmission system to be violent,but also accelerates the attenuation of the collision.The rigid-flexible coupling dynamic model conforms more to the actual working condition.On the basis of the rigid-flexible coupling dynamics,the size of parameters such as the rotational speed,the inertia load and the gap are changed to analyze the influence of different factors on the dynamic characteristics of the system.The results show that at higher speeds the number of the motion deviation fluctuations decreases rapidly but the degree of impact and collision at the start-up is high.Also,the reasonable value of the gap size to maintain the optimal working condition of the system is obtained.Finally,the 2K-H planetary gear transmission system used as the research object,the translation-torsion coupling model is established.The satellite antenna is regarded as a multi-body system including satellite body,planetary gear train joint,mechanical arm and antenna reflection surface.The satellite antenna multi-body model is built up.The influence of nonlinear factors such as gear backlash,meshing error,friction force,coupling error and heat effect on the pointing accuracy of the antenna is analyzed emphatically in the case of a double planetary gear joint.The numerical simulation results show that the suitable tooth side clearance can avoid the latches phenomenon during gear meshing and maintain high transmission precision.The choice of gear material of larger Poisson ratio can reduce the influence of gear meshing error and make it easier to keep the antenna steady in the case of low speed,uniform speed and low friction.And due to the coupling effect of the double planetary gear joint,it is more likely to cause the fluctuation of the antenna pointing accuracy deviation. |
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