ZHU Jingyuan1,2,WANG Jian1,2,DING Zehua1,2, ZHOU Hui1,2,CAO Yi1,2,3,4
JOURNAL OF VIBRATION AND SHOCK. 2018, 37(18): 9-17.
In order to study the effect of joint clearance on the dynamic characteristics of parallel mechanisms, a 3-CP_aRR parallel mechanism was taken as an example.First, the kinematics of the parallel mechanism was studied synthetically by analyzing the constraints.It shows that the cylindrical pair of the parallel mechanism can be equivalent to a driving-sliding pair and a passive-revolute pair.Next, a normal distribution statistic model was used to establish the kinematic model of the revolute joint with clearance in radial direction and axial direction, and a branch kinematics model was also established.The normal contact force between the joint elements was evaluated based on the Flores contact model, and the tangential contact force was evaluated according to the modified Coulomb friction model.Then, the dynamic model of the parallel mechanism with joint clearance was established based on the non-holonomic systems Lagrange equation method.Finally, the effect of revolute joint clearance on the parallel mechanism’s kinematics and dynamic response was analyzed in detail through a numerical example.In addition, compared with the parameter of standard normal distribution model, the physical meaning of defining the initial contact clearance value as μ was analyzed.The research provides a new research approach and builds a theoretic foundation for the analysis of multi-body systems with clearance.