Load distribution over threads of planetary roller screw mechanism with pitch deviation

Abstract

A model is proposed to calculate load distribution over threads of planetary roller screw mechanism (PRSM) with pitch deviation. Firstly, four kinds of machining errors of threads including pitch deviation, deviation of thread angle, division error of multiple threads and deviation of pitch diameter are analyzed, and the relationships among them are investigated. After analyzing the relationships among the errors, pitch deviation is chosen to be the main machining error to investigate because it can reflect the effects of other machining errors, and is the most influential machining error on the contact condition and deformation compatibility relationship, i.e. the load distribution of PRSM. Based on the proposed model, the effects of pitch deviation on the load distribution of PRSM are studied through numerical analyses, and load distributions under different machining precisions are analyzed. In order to experimentally verify the investigation, two PRSM samples are measured and tested under the same experimental conditions. The experimental results show that load distributions over threads will fluctuate because of the existence of pitch deviations. The pitch deviations, load distributions over threads and wear depths of threads in the samples show obvious accordance, which indirectly demonstrates the effects of pitch deviation on load distribution.

Research on Fractal Model of Load Distribution and Axial Stiffness of Planetary Roller Screw Mechanism Considering Surface Roughness and Friction Factor

“…A large number of studies on the axial stiffness and load distribution have been carried out in the past 20 years. For load distribution analysis, Zhang et al [3,4] proposed an efficient model to compute load distribution over threads of the PRSM considering the effect of the pitch deviation, and presented an effective method that the roller threads were redesigned. The results showed it was beneficial to achieve even load distribution to a certain extent.…”

“…5) Compute the distribution of the actual contact area A r and contact force F ri by Equations ( 35), (49), and (51). 6) Compute the total axial contact load (4) and recalculate the contact stiffness and contact load until |F a − F a0 |∕F a < 𝜀. 7) Compute the normal contact deformation, thread deformation, and screw shaft deformation by Equations ( 46), (3), and (12).…”

Wear Modelling of the Thread Pair in a Planetary Roller Screw Mechanism

“…Abevi et al [15] presented a hybrid model using the bar, beam, and nonlinear spring elements to compute the load distribution and axial stiffness of the PRSM. Zhang et al [16] proposed a model to calculate load distributions over PRSM threads with pitch deviation, the influence of pitch deviation on load distributions can be verified by comparing wear depths.…”

A comprehensive error analysis of the planetary roller screw mechanism

“…The results show that the load distribution and fatigue life dramatically change with the variation in the machining errors. Zhang et al 11 proposed a model to calculate the load distribution over the PRSM threads with pitch deviation. The experimental results showed that load distributions over the threads will fluctuate due to pitch deviations.…”