The Roberts approximate straight-line mechanism can be use to design new compliant linear guiding mechanism with large stroke and high precision. It is suitable for one-piece (monolithic) manufacturing due to there are no crossing parts in such a mechanism. A Roberts mechanism can be determined by four geometric parameters

and the location of the tracer P is the most important one. By analyzing the pseudo-rigid-body model of a Roberts mechanism

the location can be optimized to maximize the straight-line distance. A method based on the contour map of linearity is proposed to estimate the optimal value

then the finite element analysis is used for little adjustment. A linear guiding mechanism can be constructed by two Roberts mechanisms in parallel. Such a guiding mechanism is designed and fabricated. The finite element analysis and experimental results show that while its stroke is large than 1mm

the axis-offset can be limit within 1um