Stiffness analysis of Tripod parallel positioner and applications in aircraft assembly

To improve traditional 3-UPU parallel mechanism(PM),a 3-Tripod and 4-Tripod parallel mechanism is obtained,which has more compact structure and higher stiffness.Based on stiffness matrix represented by Jacobian matrix of the 3-Tripod,the maximum,minimum stiffness mapping and corresponding eigenvector direction mapping at each point within the workspace of the 3-Tripod are got.It is demonstrated that the PM gets a higher stiffness in the vertical direction and a lower stiffness in the horizontal direction in the workplane.The study of the Tripod PM is useful for improving the precision of aircraft assembly.