Kinematic Modeling of 3D Clearance in Revolute Joint and Its Application in Overconstrained Linkages

Joint clearance, which is always being viewed as a negative factor in most machine operations and hoped to be eliminated in previous studies, can be used to release some constraints in mechanisms, especially in overconstrained linkages. It is expected to prevent the movement of the developable structure constructed with overconstrained linkages from being stuck due to the deformation of the components. In this paper, we propose a general comprehensive model of 3D clearance for revolute joints (R-joints) and focus on the kinematic performance. From a kinematical perspective, contact modes of journal and bearing are divided into four cases by treating the point (or line, surface) contact as a single-point contact. Then, the relative motion of journal and bearing is analysed and derived by D-H method. Using the model, we present a method to study the kinematic characteristics of overconstrained mechanisms with joint clearances. The correctness of the proposed method is verified by the comparison with a numerical case.