Optimization of Mega-Frame Platforms Based on Orthogonal Design

The orthogonal design was chosen as the mega-frame platform optimizing method to find out the parameters which had the most important effect on the platforms’ performances. The mega-frame platform (MFP) was a new type of anti-vibration platform using the mega-frame theory. It was combined of the major frame and the minor frames. The parameters that had much more important effect on the MFP’ static capability were the number, height, position and stiffness of the major beams and the leg batter, stiffness of the major columns. In this paper, there were six factors, which were the diameter of the major beams (factor A), the leg batter (factor B), the diameter of the major columns (factor C), the position (factor D), the number (factor E) and height (factor F) of the major beams, in the orthogonal design. Two factors, the number and the height of the major beams, had two levels. One factor, the position of the major beams, had three levels. The other three factors had four levels. In order to use the orthogonal table L₁₆(4⁴×2³), one level of factor D was repeated. The analyses of the MFPs with different parameters under the same horizontal and vertical unequal loads show that: 1) the most important factor that effects the MFP is the diameter of the major columns, then the leg batter of the major columns; the thirdly and the fourthly factor are the position and the diameter the major beams; the height of the major beam has the least effect on the MFP’s performances; 2) the optimal MFP is C₄B₃D₄A₁E₂F₂. The mode analysis of the optimal MFP shows that the platform has high global stiffness and the equal mass and stiffness distribution. So the MFPs have the overall performance and can avoid the partial breakage under the random external loads.