Investigation on mechanical behavior of planetary roller screw mechanism with the effects of external loads and machining errors

The effects of radial force and machining accuracy were ignored in previous studies, which considerably affected load distribution and fatigue life for planetary roller screw mechanism (PRSM). This study establishes mechanical models that incorporate radial load and machining error. These models consist in using equivalent contact load and deformation to estimate axial loads, and applying Hertz contact theory and thread cumulative deformation to calculate contact loads of all threads. The results show that the contact forces over threads periodically change considering radial loads. Moreover, the load distribution and fatigue life dramatically change with the variation of machining errors. Based on load coefficient, the roller threads are modified so that the fatigue life and load distribution uniformity can be improved.