Dynamics analysis and characteristics of the 8-PSS flexible redundant parallel manipulator

The modeling methodology and the dynamic characteristics of the 8-PSS flexible redundant parallel manipulator are investigated based on some basic assumptions. Firstly, the system description and the rigid dynamic model are presented. The actuating forces with minimum norm and least quadratic sum among the possible actuating forces are achieved. Then, the kineto-elastodynamic model of the manipulator is developed by virtue of the finite element method and the substructure synthesis technique. Finally, the dynamic characteristics represented by the natural frequency, the sensitivity analysis, the energy ratios and the displacement responses of the moving platform are investigated through simulation. It is shown that the second order natural frequency is a little higher than the first order natural frequency for the 8-PSS flexible redundant parallel manipulator. The first order natural frequency is much more sensitive to the radius of the lead-screws than to the radius of the struts. From the computation of the energy ratio distribution, the mass of the moving platform should be reduced or the stiffness of the strut should be increased in order to improve the dynamic characteristic of the manipulator. For the investigated trajectory, the displacement response of the moving platform along the x direction is slightly larger than these displacement responses along the y direction and along the z direction. The angular displacement response of the moving platform rotating about the x axis is slightly larger than those angular displacement responses rotating about the y axis and about the z axis.