WANG Jian1,3, DONG Hu1,3, WANG Zhaodong1,3, LIU Junchen1,3, CAO Yi1,2,3
JOURNAL OF VIBRATION AND SHOCK. 2020, 39(5): 118-130.
In order to study effects of joint clearance on output kinematic characteristics of a parallel mechanism under flexible condition, a 3-CPaRR parallel mechanism was taken as the study object.Firstly, according to this mechanism’s spatial position relations, its kinematic laws were studied.It was shown that this mechanism’s driving cylindrical pair can equivalently be decomposed into a driving moving pair and a passive rotating one.Then, based on this mechanism’s spatial position vector model, the kinematic models of rotating joint with clearance in radial direction and axial one were established.Furthermore, various branched rotating joints with clearance’ kinematic models were also established.Secondly, based on Lankarani-Nikravesh contact force model and Coulomb friction model, various branched rotating pairs with clearance’ dynamic models in normal direction and tangential one were established.Then, forces produced due to clearance at passive joints were transferred to ones at driving joints to establish the elastic dynamic model for a 3-CPaRR parallel mechanism with joint clearance.Finally, effects of different joint clearances on this parallel mechanism’s kinematic responses were analyzed with actual examples.The results showed that flexible branches with joint clearance significantly affect output kinematic characteristics of a parallel mechanism; the study results provide a theoretical basis for elastic dynamic modeling of other multi-body systems with joint clearance.