A mathematical model for load distribution of planetary roller screw with pitch deviation

In this work, a mathematical model for load distribution of planetary roller screw mechanism with pitch deviation is proposed. The load distribution coefficient on the screw–roller and nut–roller sides is determined based on the relationship between axial contact stiffness, axial contact deformation and axial load. The presented model considers the variations of the axial clearance and contact state caused by the pitch deviation and is verified by comparing with the published model. Furthermore, the effects of one-thread pitch deviation, multi-thread pitch deviation and axial applied load on the load distribution coefficient of planetary roller screw mechanism are investigated. The results show that reducing the pitch deviation and increasing the axial applied load are conducive to improve the uniformity of load distribution and avoid the empty load of thread pairs. It is found that the increase of axial applied load is beneficial to reduce the load distribution fluctuation of planetary roller screw mechanism with pitch deviation.