| This thesis introduces contact-aided compliant mechanisms (CCMs), which use only elastic deformation and intermittent contacts to transmit force and motion, and develops systematic methods to synthesize them. Judicious use of intermittent contacts enables CCMs to exhibit non-smooth kinematic and kinetostatic behavior as well as the ability to tailor their stiffness as needed by a task. The contact-induced unilateral displacement constraints that make this possible also give rise to non-differentiability in the optimization-based CCM synthesis problem. Consequently, smooth optimization algorithms that are proven to be efficient for compliant mechanism design become unsuitable for this problem. In order to circumvent this difficulty, regularized normal contact modeling is proposed for small and large deflection CCM synthesis problems. This model, which has a single tunable parameter, is used to transform the non-smooth problem into a sequence of smooth approximations that can be solved efficiently.; The above methodology is used to design CCMs for a variety of non-smooth responses with a single monotonic input, using the framework of beam-element based topology optimization. Design examples are used to illustrate that interesting non-smooth force-deflection behavior can be obtained with CCMs even in the small-deflection regime. Non-smooth path generation is demonstrated by designing a CCM that undergoes large deflections. The reliability of the design method is enhanced by an objective that uses Fourier shape descriptors for shape comparison and a robust arc-length based nonlinear finite element analysis technique. Detailed case studies of two CCMs, one that produces a pair of non-smooth curves with a single reciprocating input and the other that functions as a mechanical cycle-doubler, are included to address the aspects not accounted for in the systematic synthesis procedure. |
