Designing distributed compliant mechanisms with characteristic stiffness

A novel method is proposed in this paper to address the cutting-edge problem of topology optimization of distributed compliant mechanisms, which requires the design to possess both large output displacements and evenly distributed compliance simultaneously. The design is represented by a level-set model that precisely specifies the distinct material regions and their sharp interfaces as well as the geometric boundary of the structure, capable of performing topological changes and capturing geometric evolutions at the interface and the boundary. Existing techniques for eliminating de facto hinges in the design are reviewed. Further, the intrinsic deficiencies in the widely used "spring model" are discussed and a new formulation considering the "characteristic stiffness" of the mechanism is proposed. The proposed method is demonstrated with benchmark examples of compliant mechanism optimization. The result is a design with evenly distributed compliance and a more desirable characteristic, which uniquely distinguishes our method.