Tribo-dynamics modeling of cycloidal gear-pin pair considering transient effects

Abstract

Rotating vector (RV) reducers are widely applied in heavy-duty robotics, yet their stability is often compromised by friction and wear at the interface between the cycloidal gear and pins. This study establishes a novel tribo-dynamics model specifically for the cycloidal gear-pin pair, filling a critical research gap in RV reducer analysis. Considering the transient effects such as pin motion and oil film squeezing, the model accurately captures the dynamics behavior, revealing that the pins follow an “$\infty$”-shaped trajectory which significantly reduces the interface load compared to traditional fixed-pin assumptions. Furthermore, the analysis shows that asperity contact becomes the dominant load-bearing mechanism during the late stage of engagement, when pin motion disrupts the lubricating oil film. The model also successfully predicts the wear region of the cycloidal gear with high accuracy; the simulated results are in good agreement with the experimental ones. These findings demonstrate the importance of considering the transient effects to enhance the understanding of lubrication, friction, and wear mechanisms in RV reducers, ultimately supporting enhanced reliability and service life.