Spatial Stiffness Analysis of the Planar Parallel Part for a Hybrid Model Support Mechanism

Abstract

The hybrid aircraft model support mechanism is subjected to six directional forces in the experiment, and high spatial stiffness requirement of the parallel part is the guarantee for the stability of the aircraft model. The purpose of this paper is to obtain a planar parallel part with relatively good spatial stiffness and to explore the influence of components on the stiffness characteristics. We employed screw theory and virtual work principle to establish the spatial stiffness model of two possible parallel parts for the support mechanism. The stiffness characteristics of the two parallel mechanisms were evaluated by a desired trajectory sub-workspace deformation distribution and two novel stiffness indexes. According to deformation distributions of the sub-workspace, the deformation of typeI is smaller than that of type II. The proposed indexes indicate that the influence of the hydraulic cylinder range on the stiffness of type II is more significant; RVR of ASI is 263.5%, RVR of CSI is 18.1%. These reveal type I has better spatial stiffness than type II. The reason is that the guideway of type I provides a part of the ability to resist external forces.

Keywords

• spatial stiffness
• planar parallel mechanism
• stiffness index
• screw theory
• model support mechanism
• active stiffness