A Millimeter-Range Actuator With Submicron Precision: Principle and Application

The macro–micro machining is an important method for the robotic high-precision machining, although the harsh machining process demands highly on the stiffness, force density, and stroke-volume ratio of the micromotion actuator. In response to these challenges, this work proposes a novel hydraulic micromotion actuator with corrugated diaphragms. First, the driving principle of the actuator is proposed, followed by an investigation into the parameter design and optimization of the actuator. Second, a dynamical model for the actuator is established, and a sliding mode controller has been developed to handle the strong nonlinear behavior of the electrohydraulic system. Finally, the prototype of the actuator is manufactured and tested. The results demonstrate that the actuator, measuring <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{\phi 120\times 20}$</tex-math></inline-formula> mm, delivers a stroke of 1.56 mm without external force. The actuator is capable of achieving a stroke of 1 mm up to an external load of 3745 N. The actuator exhibits a bandwidth of 165 Hz, a resolution of 0.1 μm, and a closed-loop stiffness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{5.4024\times 10^{4}}$</tex-math></inline-formula> N/mm, which exceeds the typical stiffness observed in industrial robots. Furthermore, the proposed actuator outperforms the existing millimeter-range micro positioning actuators in terms of stroke-volume ratio and force density.