A 3D-printed 3-DOF tripedal microrobotic platform for unconstrained and omnidirectional sample positioning

Abstract

This paper describes the design of a 3D-printed, three-degree-of-freedom (3-DOF) tripedal microrobotic platform that is capable of unlimited travel with sub-micrometer precision over a planar surface. The design combines piezoelectric stack actuators with compliant mechanical amplifiers to create stick-slip-style mechanisms for locomotion. A forward kinematic model of the stage’s motion is derived from its tripedal leg architecture. The model is then inverted for feedforward control of the platform. A prototype of the microrobot is constructed using low-cost 3D-printing technology. Experimental results demonstrate actuator stroke of 29.4 $$\upmu$$ m on average with a dominant resonance of approximately 860 Hz. Using open-loop feedforward control, the stage travels along a 3 mm $$\times$$ 3 mm, rectangular path. Feedback control through visual servoing is then simulated on a model that includes flexure dynamics, observed surface interactions, and camera sampling times, reducing the root-mean-square (RMS) tracking error by 90%. This controller is then implemented experimentally, resulting in 99% RMS position error reduction relative to feedforward-only control structure. The results show feasibility of creating functional 3D-printed, 3-DOF sample positioning stages.