A micro scratching platform with cross-scale plane trajectory tracking capability

A novel two-degree-of-freedom (2-DOF) micro scratching platform driven by inchworm type piezoelectric actuator with parallel mechanisms is proposed, designed, fabricated, and tested aiming for accomplishing cross-scale plane trajectory tracking. Through the hybrid compliant notch parallelogram flexure hinges (HCNPs), the actuation mechanism can realize output decoupling and parasitic displacement limitation simultaneously, which is of great importance to improve the positioning precision. The structural stiffness and maximum stress are analyzed through theoretical modeling and finite element modeling of HCNPs. The symmetric operating mode of parallel actuator accomplishes plane motion using only six driving and clamping elements, and the trajectory tracking control strategy is completed based on it. The results indicate that the scratching platform can implement 2-DOF decoupled motion with a travel range of 40 × 40 mm2, and the minimum step distance is 0.78 µm. The precise planar synthesis is also accomplished and the open-loop trajectory synthesis errors are lower than 2.87 %. Besides, the triangular and circular trajectories with depth of 1 µm are one-step scratched successfully due to the high horizontal payload capacity up to 41.5 N. Moreover, the platform has potential to be used in probe tip-based micro scratching for other planar trajectories.