Meshing characteristics of planetary roller screw mechanism with multiple roller considering manufacturing and assembly errors

Abstract

A comprehensive multi-roller meshing model is developed to address the unclear coupling mechanisms through which manufacturing and assembly errors influence the meshing characteristics of the planetary roller screw mechanism. This model is employed to analyze the patterns of contact point distribution and axial clearance variation. First, a multi-roller contact analysis coordinate system considering assembly errors is established based on the theory of homogeneous coordinate transformation. Subsequently, manufacturing errors are parameterized as additional correction terms integrated into the thread surface equations, thereby constructing a mathematical model of the thread surface with errors. Then, by solving nonlinear equations under geometric contact constraints, the meshing point radius and the minimum axial clearance under different error combinations are obtained. This process reveals the coupling influence law of manufacturing and assembly errors on the meshing characteristics. Finally, an equivalent relationship between coupled errors and the roller’s limiting error is proposed, and an optimization model for the thread tooth thickness targeting axial clearance is established to expand the error tolerance of the planetary roller screw mechanism. The results demonstrate that a negative pitch diameter error exhibits a significant negative coupling effect with other errors, while positive coupling characteristics are observed among the remaining errors. The optimized thread tooth thickness model increases the minimum axial clearance under comprehensive error conditions from −1.5 to 2.3 μm, thereby significantly improving assembly feasibility.