Abstract
Based on the differential principle of thread transmission, an analytical model considering helical directions between screw and roller threads in planetary roller screw mechanism (PRSM) is presented in this work. The model is critical for the design of PRSM with a smaller lead and a bigger pitch to realize a higher transmission accuracy. The kinematic principle of planetary transmission is employed to analyze the PRSM with different screw thread and roller thread directions. In order to investigate the differences with different screw thread and roller thread directions, the numerical model is developed by using the software Adams to validate the analytical solutions calculated by the presented model. The results indicate, when the helical direction of screw thread is identical with the direction of roller thread, that the lead of PRSM is unaffected regardless of whether sliding between screw and rollers occurs or not. Only when the direction of screw thread is reverse to the direction of roller thread, the design of PRSM with a smaller lead can be realized under a bigger pitch. The presented models and numerical simulation method can be used to research the transmission accuracy of PRSM.
Highlights
Planetary roller screw mechanism (PRSM) is used in various motion-delivery devices where power is transmitted by converting rotary motion to linear motion
When the helical direction is identical between the screw thread and the roller thread, the relationships of helical direction in PRSM are as follows: screw is right-hand, roller is right-hand, and nut is right-hand
This paper develops the kinematics by analytical modeling and numerical modeling of the PRSM considering helical directions between screw thread and roller thread to provide a method to support its design and application
Summary
Planetary roller screw mechanism (PRSM) is used in various motion-delivery devices where power is transmitted by converting rotary motion to linear motion. The results indicate that the roller migration does not affect the overall lead of the PRSM They have applied the principle of conjugate surfaces to the contact kinematical modeling at the screw-roller and nut-roller interfaces [13]. There is no comprehensive kinematics model that can apply differential principles to the design or estimate the lead of PRSM, when the helical directions between the screw thread and the roller thread are considered. To address the aforementioned problems and facilitate the PRSM design, a kinematic model and a comprehensive study on the helical directions between screw thread and roller thread based on differential principle of thread transmission are developed in this work. Kinematics simulations of the PRSM are performed to validate the motion analysis which considers the helical directions between the screw thread and the roller screw. The models are examined in detail to explicitly show the relationships of the helical directions and the lead of the PRSM in the force analysis
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