Kineto-Elastodynamic Characteristics of the Six-Degree-of-Freedom Parallel Structure Seismic Simulator

Abstract

Based on the kineto-elastodynamic assumptions, the dynamic model of the six-degree-of-freedom parallel structure seismic simulator is developed by virtue of the finite element method and the substructure synthesis technique. The kineto-elastodynamic characteristics represented by the natural frequency, the sensitivity analysis, the energy ratios, and the displacement response of the moving platform are investigated. It is shown that the second-order natural frequency is much higher than the first-order natural frequency, and the first-order natural frequency is sensitive to the radius of the strut and the radius of the lead screw. In order to improve the dynamic characteristic of the manipulator, the mass of the moving platform should be reduced or the stiffness of the strut should be increased especially for the sixth strut. For the investigated trajectory, the displacement response of the moving platform along the x direction is smaller than these displacement responses along the y direction and along the z direction. The angular displacement response of the moving platform rotating about z-axis is slightly larger than those angular displacement responses rotating about the x-axis and about the y-axis. ⎡ ⎣ U si (1 : 18, 1 : 1) U ci ⎤ ⎦ , M ki = ⎡ ⎣ M si (1 : 18, 1 : 18) M si (1 : 18, 21 : 21) M si (21 : 21, 1 : 18) M si (21 : 21, 21 : 21) + m ci ⎤ ⎦ i = 1, 2, 3, M ki = ⎡ ⎣ M si