Online monitoring of the axial thermal displacement of machine tools using a laser mouse sensor

Abstract

We present a low-cost online system for monitoring the axial thermal displacement of machine tools. The proposed monitoring system includes an embedded optical sensor derived from a laser mouse; an image acquisition microcontroller; speckle patterns; and an edge computer that hosts software, including an image display module, a displacement calculation module, an image enhancement module, and a data visualization module. The proposed sensing system can measure the displacement in two orthogonal directions simultaneously by employing digital image correlation; thus, the proposed system is a two-dimensional displacement sensor. The sensing system is benefited from image enhancement techniques and customized optimal speckle patterns printed using a standard low-cost monochrome laser printer. Experimental results indicate that the proposed displacement sensing system has an accuracy and a precision of <5 μm in both orthogonal directions. The two-dimensional displacement sensing system was used for the online monitoring of the thermal deformation of a feed drive system for machine tools, and the performance was assessed experimentally. The complete procedure for measuring the displacement due to thermal deformation was conducted automatically and can be completed in 2 min using a program coded in a computer numerical control controller.