Topology optimization of hinge-free compliant mechanisms under a maximum rotation constraint

This article presents a novel approach for the design and optimization of compliant mechanisms in micro-mechanical systems. Traditional topology optimization often leads to the formation of virtual hinges characterized by excessive rotation. To address this limitation, a new design methodology is proposed that incorporates rotation as a constraint, effectively controlling the formation of virtual hinges. The proposed approach introduces a topology optimization framework with a constraint on the maximum allowable rotation, ensuring that design solutions remain within the linear strain regime. In addition, an adjoint-based sensitivity analysis is employed to facilitate efficient evaluation of the impact of design variables. The efficacy of the proposed method is demonstrated through benchmark numerical examples, including the flexible gripper, reverse gripper and steering mechanism. A three-dimensional (3D) gripper design is experimentally validated through 3D printing, confirming that the rotational deformation constraint significantly reduces undesirable deformations, thereby enhancing both structural robustness and functional performance.