  In topology optimization of compliant mechanisms, the specific placement of
boundary conditions strongly affects the resulting material distribution and
performance of the design. At the same time, the most effective locations of
the loads and supports are often difficult to find manually. This substantially
limits topology optimization's effectiveness for many mechanism design
problems. We remove this limitation by developing a method which automatically
determines optimal positioning of a prescribed input displacement and a set of
supports simultaneously with an optimal material layout. Using nonlinear
elastic physics, we synthesize a variety of compliant mechanisms with large
output displacements, snap-through responses, and prescribed output paths,
producing designs with significantly improved performance in every case tested.
Compared to optimal designs generated using best-guess boundary conditions used
in previous studies, the mechanisms presented in this paper see performance
increases ranging from 47%-380%. The results show that nonlinear mechanism
responses may be particularly sensitive to boundary condition locations and
that effective placements can be difficult to find without an automated method.
