Special positions of body-and-cad frameworks

James Farre, Audrey Lee-St.John, Jessica Sidman, Louis Theran— 2013

- Focus Area 1: High-complexity Geometry - A recent result provides a combinatorial characterization of the generic rigidity for the majority of Computer Aided Design (CAD) structures. However, an algorithm based on this result will incorrectly classify a design as well-constrained if it is in a special (non-generic) position allowing an internal motion. Since, in practice, CAD users often rely on highly organized structural elements and design patterns which may exhibit this non-generic behavior, we seek an approach to determine whether a design is in a special position. We present a combinatorial approach for finding the factors of the polynomial whose vanishing indicates a special position. For certain structures, we further find geometric properties determining when factors of the polynomial vanish by using the Grassmann-Cayley algebra and present case studies demonstrating our approach.

TitleSpecial positions of body-and-cad frameworks
AuthorJames Farre, Audrey Lee-St.John, Jessica Sidman, Louis Theran