Dynamics analysis of 6-SPS parallel mechanism with S pairs clearance

Abstract

ABSTRACT Based on the Lagrange equation, the dynamic equation of the ideal 6 – SPS parallel mechanism and the variation curve of the torque of the mechanism are obtained. Then, the dynamic characteristics of 6 – SPS parallel mechanism with 6 S pairs’ clearances are concerned with the continuous contact model. The S pair’s clearance of the moving platform is simplified to a non-mass linkage, and its length is represented by random function; the lubricating oil film is simplified as a spring, and the oil film thickness is simplified as the length of the linkage and the stiffness of the spring is taken as the stiffness of the linkage’s massless. Therefore, the dynamic equations of mechanism with clearances are obtained. When the dynamic equations of the mechanism had been analysed, it was obtained that the torque variation curves of the branched chain with clearance mechanism was. It was shown that the stiffness of the linkage had little effect on the moment of the mechanism by the simulation results. It was found that the torque of the mechanism was increased with the increase of the clearance after the torque curves of the ideal mechanism and the mechanism with clearance was analysed, so did the fluctuations. Thereby it was indicated that the clearance of S pair had significant effects on the state of the mechanism’s force. In addition, the change of the angular velocity of the moving platform has no significant effect on the fluctuation of the moment curve. However, the change of the angular displacement curve frequency of the moving platform has more influence on the torque than the angular displacement amplitude.