The Effects of Joint Clearance on the Dynamics of the 3-RPR Planar Parallel Manipulator

In reality, clearances in the joints are inevitable due to the defects arising from manufacturing process, design tolerances, and wearing after a certain working period. It leads to a chaotic behaviour including the impact loads which results in an unpredictable response in the system. Since clearance introduces an additional uncontrollable degree of freedom to the manipulator, it causes error and could not be neglected in the manipulator design. In this study, the dynamic behaviour of a planar mechanism with revolute joints, in the presence of clearances is investigated. The planar 3-RPR parallel manipulator with six revolute clearance joints is modelled in MSC.ADAMS software and the simulation results are presented. Moreover, the effects of clearance size on the dynamic characteristics of a planar mechanical system are analysed and compared. What is found out is the prediction of the dynamic error due to the joints clearance for this parallel robot.