Dynamic modeling and analysis of spatial parallel mechanism with revolute joints considering radial and axial clearances

Due to manufacturing and assembly errors, there are clearances in the mechanism, which reduces motion precision and working performance of the mechanism. Revolute joint is one of the most widely used joints in the mechanical system. Most researches only consider the radial clearance of revolute joint, but in fact there are both radial and axial clearances; this makes it impossible to master influence of revolute clearance joint on dynamic characteristics of the mechanism. As a kind of spatial parallel pointing mechanism, 3-RRRRR mechanism needs high precision. In order to accurately predict the dynamic characteristics of the mechanism, a modeling method of revolute joint considering both radial and axial clearances is derived, and a modeling method of spatial parallel mechanism considering spatial revolute clearance joint is proposed. On this basis, the dynamic model of 3-RRRRR mechanism with clearance is developed. The Runge–Kutta method is used to analyze the dynamic response of the mechanism when the axial clearance is considered or not. The necessity of the existence of the axial clearance is verified. Then, the dynamic response of the mechanism with different clearance sizes and numbers is analyzed, and the results are compared with virtual prototype simulation to verify the correctness of the mathematical model. Through the analysis, this paper verifies that the axial clearance cannot be ignored and provides a theoretical basis for predicting the effect of spatial revolute clearance joint on the dynamic characteristics of the mechanism and lays a good foundation for the manufacture and application of the mechanism.