Research On Dynamic Characteristics Of RV Reducer

As the mainstream reducer of robot joints,the RV reducer plays an important role in the precision of both transmission and motion for an industrial robot.However,the domestic RV reducer has the problems with vibration and noise generally,and the dynamic characteristics are to be improved.In this paper,taking the RV40E-121 reducer as an example,the study of the dynamic characteristics of the RV reducer is carried out to find the main factors affecting its inherent characteristics and analyzes what the effects of cycloidal meshing characteristics are due to the changing of structure parameters of cycloidal gear.All of these studies aim at solving the problem of vibration and noise of RV reducer.This paper gives theoretical advice on structural optimization and the selection of design parameters of cycloidal gear to avoid the blindness.In this paper,influences of different modification parameters and eccentricities on the meshing characteristics of the cycloidal pair are studied on the basis of a cycloidal gear with negative moved distance modification and negative equidistance modification.And the correctness of the conclusion is verified by dynamic simulation.The research shows that:(1)With the increase of absolute value of moved distance modification,the number of teeth that the cycloidal pair will engage at the same time will decrease.Besides,the equivalent mesh stiffness of them will be smaller and smaller,and the meshing force will be bigger and bigger.(2)With the increase of absolute value of negative equidistance modification,the number of teeth that the cycloidal pair will engage at the same time will increase.Besides,the equivalent meshing stiffness of them will be bigger and bigger,and the meshing force will be smaller and smaller.(3)With the increase of the eccentricity of cycloidal gears,the number of mesh teeth will decrease,but the meshing force will decrease,and the equivalent mesh stiffness will increase gradually.The research uses the lumped mass method to establish a mass spring model of RV reducer.By translating the rotation displacement of each component into a linear displacement,a disc analysis model considering torsional deformation was built by Lagrange method.According to the Matlab program solution to the model,the research gets the natural frequency and vibration mode.Basing on the sensitivity of the quantitative and qualitative analysis of system parameters,the research finds the influence of different structural parameters on the inherent characteristics:(1)The main factors affecting the RV reduction system is the rotation inertia of planet carrier and the bearing stiffness on it.(2)When the natural frequency of a "low sensitive" part is close to its characteristic frequency or the natural frequencies of RV reducer,its appropriate modification on quality parameters or stiffness parameters does not affect the inherent frequency of the whole machine,so it is not necessary to consider whether the second resonance will occure.An experiment of RV40E-121 was carried out for the modal analysis,the research obtains the first two order natural frequencies of the reducer.The research compares them with the values calculated by the mathematical model and analyzes sources of the value error.The results show that it is still effective to use the theory of dynamic model to predict the first natural frequency of RV reducer.Besides,the research gets the natural frequencies of main parts respectively in the actual working conditions by the finite element method and compares their natural frequencies with their characteristic frequencies and the inherent frequency respectively.The results show that: in the rated working conditions,resonance will not happen to any parts of the RV reducer.The dynamic characteristic of the reducer is good.