A Coupled Contact Dynamics Model for the Thread and Gear Pairs Considering Multisource Nonlinear Factors

Synchronous meshing of thread and gear pair is one of the important characteristics of the planetary roller screw mechanism (PRSM), which will have a key impact on the dynamic performance of the whole mechanism. At present, the research on dynamics of PRSM considering nonlinear factors mainly focuses on the thread pair, but the coupling effect of thread and gear pair has not been involved. Considering nonlinear factors such as clearances, errors, and contact stiffnesses of the thread and gear pair, a coupled contact dynamics model for the thread-gear pairs is established. The correctness of the presented model is corroborated by comparing the contact forces on the thread and gear pairs with and without the influence of nonlinear factors mentioned above. In addition, the influence of clearances, errors, and contact stiffnesses of the thread and gear pairs on contact forces is analyzed. The results indicate that as thread clearance increases, thread contact force decreases while gear contact force rises. The gear pair clearance does not affect the thread pair contact force. The errors in pitch and pressure angle have a meaningful impact on the contact force of both thread and gear pairs. Increased thread normal stiffness: roller-screw force dips, then peaks; gear force peaks, then dips. Higher gear meshing stiffness elevates thread contact force.