ANALYSIS ON THE MULTIPLE BIFURCATION IN THE KINEMATIC PATH OF SPATIAL PIN-BAR MECHANISMS

Kinematic bifurcation is an important theoretical problem for the kinematic analysis of pin-bar mechanisms. Based on FEM, the basic kinematic equation of pin-bar linkages was established, and the multiple bifurcation characteristics of the kinematic path were discussed. The bifurcation condition of the kinematic path was explicated theoretically. The conventional method for pinpointing singular point was improved to adapt to the multiple bifurcation problem. A disturbing force vector, which depends on the eigenvectors of tangential stiffness matrix, was introduced into the arc-length method to trace the multiple bifurcation paths. A simplified spatial pin-bar Pantadome linkage was employed as an illustrative example. The lifting process of the linkage was numerically simulated. Using the proposed method, the singular points in the kinematic path are effectively identified, and multiple bifurcation paths are also traced.