A Multi-layer Parallelogram Flexure Architecture for Higher Out-of-Plane Load Bearing Stiffness

Abstract Parallelogram Flexure Mechanism (PFM) is a common flexure module which is widely used as a building block in the design and manufacturing of flexure-based XY motion stages that provide in-plane Degrees of Freedom (DoFs). In such motion stages, low in-plane stiffness along the DoF helps increase the DoF range of motion and reduce the actuation effort. At the same time, high out-of-plane stiffness is paramount to suppress out-of-plane parasitic motions, support heavy payloads and mitigate the negative impacts of out-of-plane resonant modes. Achieving both of these design objectives simultaneously is extremely challenging in PFMs and flexure mechanisms comprising PFMs due to the inherent tradeoff between the in-plane and out-of-plane stiffness. This paper resolves this tradeoff by proposing a novel multi-layer PFM architecture, referred to as the sandwich PFM, that achieves a significant improvement in the out-of-plane translational and rotational stiffness compared to conventional single-layer PFMs without impacting the in-plane DoF stiffness. Analytical models will be derived for the in-plane and out-of-plane stiffness of the sandwich PFM that closely match with the Finite Element Analysis (FEA) results. Several design insights into the performance of the sandwich PFM are discussed using the analytical stiffness models and a general procedure is proposed to design a sandwich PFM.