Embedded Sensor System for Five-degree-of-freedom Error Detection on Machine Tools

Abstract

Any linear stage of machine tool has inherent six-degree-of-freedom (6-DOF) geometric errors. Its motion control system, however, has only the position feedback. Moreover, the feedback point is not the commanded cutting point. This is the main reason why the positioning error along each axis and the volumetric error in the working space are inevitable. This paper presents a compact 5-DOF sensor system that can be embedded in each axis of motion as additional feedback sensors of the machine tool for the detection of three angular errors and two straightness errors. Using the derived volumetric error model, the feedback point can be transferred to the cutting point. The design principle of the developed 5-DOF sensor system is described. An in-depth study of systematic error compensation due to crosstalk of straightness error and angular error is analyzed. A prototype has been built into a three-axis NC milling machine. The results of a series of the comparison experiments demonstrate the feasibility of the developed sensor system.