Design and Analysis of Ultra-Precise Large Range Linear Motion Platforms Using Compliant Mechanism

Double parallelogram compliant mechanism (DPCM) is extensively used to obtain precise straight-line motion. Symmetric DPCMs, used previously, traverse a straight-line path without parasitic error when gravity vector is perpendicular to the plane of bending of beams. However, when gravity vector is either in line with beams (orientation B) or in the plane of bending of beams (orientation C), asymmetry in the loading causes undesired deviation from a straight-line path. This undesired deviation called parasitic error increases, especially in beams with relatively low flexural rigidity required to obtain larger displacements with low power actuators. This paper first characterizes parasitic error, in such cases, using large deformation analysis and further proposes novel ways to minimize it. A recently developed, chained beam constraint method is used to model, characterize, and optimize DPCMs. Optimized parameters are further validated by FEA and experiments. In orientation B, after implementing the proposed method, numerical analysis and experimental results show that the undesired parasitic error of $\mathrm {123 ~\mu \text {m} }$ is drastically reduced to $\mathrm {2 ~\mu \text {m} }$ and $\mathrm {6 ~\mu \text {m} }$ , respectively. Moreover, systematic design procedure with corresponding graphs is presented to avoid modeling and optimization steps for a user-specific case. The proposed methods pave pathways to reducing the parasitic error during large-range motion using multiple orientations of DPCMs and thus make DPCMs more employable in several precision motion applications such as 3D optical scanners, 3D micro-printers, CMM probes, and microscopy stages.