Dynamical Model of RV Reducer and Key Influence of Stiffness to the Nature Character

For the RV reducer used in Robots, based on different characteristics of involutes gear and cycloid gear, taken into account the influence of support bearing´s stiffness and the angle periodic variation between the crankshaft and the cycloid gear, applying Newton´s second law and the generalized coordinates method, the 25-DOF dynamical model by lumped-parameter method has been established. Results show that the nature frequency of the RV reducer changes at a tiny range with the rotation of the cycloid gear, the support bearings stiffness of planet carrier and the bending stiffness of crankshaft has obvious effect on the nature frequency. Furthermore, sensitivity analysis of bearing stiffness to the nature character has been analyzed, and the results show that the nature frequency will be larger than 750 Hz when the support and arm bearings have higher stiffness. But the stiffness will decrease quickly when the bearings have tiny clearance caused by assembling or by fatigue. These can produce multi-stage lower nature frequency less than 380Hz, and result in the vibration or flutter of the system. In order to avoid resonance and keep the precision of RV reducer, the support and arm bearings should be designed and assembled as high stiffness.