Design of a Stewart-Gough Platform for Engineering Material Characterization

Stewart-Gough platforms have been used as the basis for multiaxial test machines in multiple applications. Their stiffness coupled with the ability to simultaneously create a combined loading (tensile/bending/twisting) of any design enables them to excite material parameters in any conceivable coupling. For engineered materials, whose properties are often nonlinear and nonisotropic, such loadings are necessary to understand the as-built material parameters inherent within these designed systems. However, the design of a Stewart-Gough is nontrivial as the presence of singular configurations is poorly understood. In the proximity of these singular configurations, precision control of the loading applied by the system is difficult to control due to large gradients in the forces generated. This work uses a combination of simulation and surrogate modeling to establish a “map” of the singular configurations of the Stewart-Gough platform. As a result, a “home” location where the system provides a zero loading upon a specimen is found so as to maximize distance from a singular configuration, and a greater understanding of the nature of singularities in parallel robotics structures is obtained.