The inverted recirculating planetary roller screw mechanism is a novel transmission screw that enables integrated nut-motor design, simplified fabrication, high load capacity and long service life. The nut engages with multiple annular-grooved rollers, which further mesh with the screw threads to transmit power. This paper first proposes an innovative structural design of the inverted recirculating planetary roller screw mechanism, derives the dimensional range of the screw’s unthreaded section, establishes the parameter matching equations for the mechanism components, and performs a virtual modeling. Next, the calculation formulas of the motion parameters of the inverted recirculating planetary roller screw mechanism are derived. Then, a dynamic simulation model is developed using ADAMS software, and the results are compared with the theoretical ones, with a relative error ranging from 0.25% to 1.12% being obtained, which validates the feasibility of both the simulation approach adopted in this study and the proposed mechanism. Finally, the variation patterns of the thread contact force as well as the collision force between the rollers and the boss slope in the inverted recirculating planetary roller screw mechanism are quantitatively analyzed from two aspects: the operating condition parameters and the inclination angle of boss inclined plane. It is found that the axial contact force in the threaded section is minimally affected by the rotational speed and the boss inclination angle, but is significantly influenced by the external load; that the average axial contact force increases markedly with the external load; and that the collision force between the rollers and the cam ring boss slope increases with the increase of nut’s rotational speed and screw load, but decreases significantly with the increase of boss inclination angle. The research results of this paper provide certain reference for optimizing the design of the inverted recirculating planetary roller screw mechanism.

The recirculating planetary roller screw mechanism, as a derivative of planetary roller screw mechanism, is a transmission mechanism that is engaged by the screw or nut thread and multiple circular groove rollers. To study the random vibration fatigue characteristics of the recirculating planetary roller screw mechanism, this paper established a finite element model of the mechanism based on fatigue failure theory, and conducted the dynamic analysis and fatigue life prediction. Firstly, according to the material stress-number of cycles (S-N) curve and Miner’s linear damage accumulation theory, fatigue analysis was carried out on the recirculating planetary roller screw mechanism using the related software, and fatigue results in the contact area and damage values at each node were obtained. Then, based on the developed four fatigue life prediction models, the obtained analytical solutions were compared with the simulated damage values. The results show that the resonance induced by the recirculating planetary roller screw mechanism at 3960 Hz causes the most damage to the mechanism. When the excitation frequency is the same, the area of maximum contact stress and minimum fatigue life is the same. Besides, the corresponding frequencies of the peak stress in the harmonic response analysis and that of the peak power spectral density in the fatigue analysis of the recirculating planetary roller screw mechanism are the same. This study can provide a theoretical guidance for the design and fatigue optimization of the recirculating planetary roller screw mechanism.

The recirculating planetary roller screw mechanism is a transmission mechanism that is engaged by the screw or nut thread and multiple circular groove rollers. This study theoretically analyzed the working principle and motion relationship of the recirculating planetary roller screw mechanism, and established the 3D model of the recirculating planetary roller screw mechanism. The 3D model was imported into the multi-rigid-body dynamics simulation software ADAMS, and the reasonable connection relationship of virtual prototype was set. The dynamics analysis was carried out and related parameters such as angular speed, velocity, force and torque were extracted. The results show that the simulated value of roller angular speed is 28.28 rad/s, the angular speed of roller is -5.20 rad/s, the nut movement velocity is 1.98 mm/s, and the nut displacement is 2 mm. The above values were compared with their corresponding theoretical values, and the error was found to be less than 5%, thus verified the correctness of the simulation results. The contact force of the roller contacting with the screw and the nut respectively presents sine curve characteristics in the nut threadless area. When the load is 5, 10 and 15 kN, the maximum peak of the collision force between the same roller and convex platform of cam ring under different loads are 113.92, 32.31 and 54.08 N, respectively. Besides, the fluctuation range of the maximum peak of the collision force between different rollers and convex platform of cam ring under the same load is similar to the above values, thus the collision force between the roller and convex platform of cam ring peak value is not affected by the load size. The collision torque between the roller and the carrier increases under higher load; the angular speed of the roller begins to change in the nut threadless area during the operation of the recirculating planetary roller screw mechanism, and the maximum sudden change occurs at the contact between the roller and the convex platform of cam ring. This study has certain reference significance for optimizing the overall performance of the recirculating planetary roller screw mechanism.