Dynamic modeling and comparative analysis of a 3-PRR parallel robot with multiple lubricated joints

This paper presents a methodology to study the dynamic response of a parallel robot with multiple lubricated joints. Based on Gumbel's boundary conditions, the hydrodynamic force of the journal bearing is calculated with the Pinkus-Sternlicht model. Considering the dynamic loads on the multiple lubricated joints, the Pinkus-Sternlicht model is modified to ensure numerical stability of the solution of the system's equations. A comparative analysis of four joint force models is presented to show the advantages of the modified model for a 3-PRR (P and R represent prismatic and revolute pairs respectively and the underline of the P represents the actuated joint) parallel robot. The improvement in the numerical stability of the modified Pinkus-Sternlicht model is proven. Subsequently, the dynamic behavior of the 3-PRR parallel robot with multiple lubricated joints is analyzed comprehensively, compared with the 3-PRR parallel robot with multiple dry clearance joints. Simulation results demonstrate the validity of the dynamic methodology containing the modified Pinkus-Sternlicht model for the 3-PRR parallel robot with multiple lubricated joints. This dynamic methodology can illustrate the better periodicity of such parallel robots considering lubricated joints.