Fast tool servo control for diamond-cutting microstructured optical components

Abstract

In diamond-cutting microstructured surfaces, variations in cutting depth and cutting speed due to sharp-corner and step structures in some microstructured surfaces such as Fresnel lens make the control system of fast tool servo (FTS) unstable, and therefore decrease the surface quality and even lead to tool fracture. In addition, to achieve precise positioning, the control strategy for FTS must adequately eliminate the effect of piezoelectric nonlinear characteristics such as hysteresis and creep. In this article, an adaptive variable-structure sliding-mode control (VSSMC) algorithm for FTS was proposed to solve these problems. Comparative tests were conducted between the conventional proportion-integration-differentiation and the VSSMC algorithm. Testing results verify that the variable-structure sliding-mode controller is robust against changes in system parameters and disturbances of cutting forces in the cutting process. It is also able to track the command position quickly with high steady state accuracy and without overshoot.