Rectilinear translation four-bar flexure mechanism based on four Remote Center Compliance pivots

This paper presents a novel planar four-bar linkage compliant mechanism (called 4-RCC) based on four flexure-based Remote Center of Compliance (RCC) pivots. With particular configurations and dimensions, the beam shortening of the RCC pivots can compensate the parasitic shift of the four-bar linkage over its range of motion, thereby creating a rectilinear translation mechanism. Moreover, to decrease the stiffness in the direction of the desired translation, while keeping the same magnitude of the transversal stiffnesses, a fixed-guided buckled beam with constant negative stiffness is added in parallel. This stiffness compensation greatly decreases the force to actuate the stage. This paper derives the analytical conditions required to compensate both the parasitic shift and the stiffness of the 4-RCC mechanism. A mesoscale mockup model is designed, aiming for a millimeter-scale stroke, a compensated parasitic shift and a near-zero stiffness. A finite element model (FEM) validates the mechanism design and the analytical model. Simulation results show that the design leads to a parasitic shift below 65.6 nm over a displacement range of 8 mm, and the required actuation force is reduced by 95% when the buckled beam is added. Furthermore, the residual straightness error can be minimized by advantageously adjusting the preload of the buckled beam.