Advanced Sensing and Machine Learning Technologies for Intelligent Measurement in Smart and Precision Manufacturing

This paper provides an overview of state-of-the-art sensing and machine learning technologies for intelligent measurement in smart and precision manufacturing. Length, angle, and force are identified as the fundamental quantities for production quality management based on process monitoring as well as geometrical metrology in optical lithography and mechanical machining. Advancements in length-based measurement technologies such as laser interferometers and optical encoders, as well as advancements regarding depth and thickness measurements, are presented. Various types of optical microscopes, such as evanescent field microscopes, structured illumination microscopes, and confocal microscopes, are also described. For angle-based measurement technologies, in addition to the conventional continuous-wave laser autocollimators, the newly developed Fabry–Pérot angle sensor and nonlinear optics angle sensor using an ultrashort pulse laser are presented. Finally, on-machine and in-process force sensing and machining learning techniques for dimensional and machining process monitoring are reviewed.