Dynamic modelling and contact analysis of bearing-cycloid-pinwheel transmission mechanisms used in joint rotate vector reducers

Abstract A generalised dynamic model is proposed for the bearing-cycloid-pinwheel transmission mechanisms (BCPTMs) that are used in robot joint rotate vector (RV) reducers. The model can be used to investigate the effect of changing the geometrical design parameters of the tooth profile of the cycloidal gear and turn-arm bearings on the dynamic contact response and internal-load transmission characteristics of the BCPTM. Contact analyses are conducted for the meshing of the multi-tooth cycloid-pinwheel transmission system and the multiple contact points of the turn-arm bearings. This allows us to judge the contact positions, calculate the contact loads, update the generalised force acting on the system and reassemble the dynamic equation for the system. To investigate the effectiveness of the model, a typical BCPTM composed of two cycloidal gears, three crankshafts and six turn-arm needle roller bearings is analysed. On this basis, the internal load-transmission characteristics and dynamic contact response of the transmission mechanism are elucidated considering the clearance of the cycloidal gear pairs and the radial clearance in the bearings. The research reported provides a sound theoretical basis for the analysis of the carrying capacity of RV reducers used in industrial robots.