This work presents the development of a laser tracking Doppler vibrometer (TLDV), which is based on a laser scanning vibrometer improved for tracking the same point of a bladed disk during a complete circular rotation, so that a Lagrangian approach can be applied to vibration measurement of a rotating object. The TLDV is presented and applied to the measurement of vibration velocity map of a rotating object. Measurements have been carried out on a bladed disk rotating up to 62 rps. This article discusses the development of the measurement system, with particular attention to the problems of measurement uncertainty and laser spot positioning accuracy. Results of TLDV measurements performed under different conditions of rotation and of vibration are presented. An analytical model of the measurement system was developed in order to evaluate its behavior and analyze its accuracy on the positioning and uncertainty of the measured data. In this way it was possible to identify the most critical elements in the system and to guide its optimization. The misalignment between the optic axis of the tracking system and the rotation axis of the object is the most relevant source of uncertainty, inducing the presence of pseudovibrations at the frequencies of rotation and causing relative motion of the laser beam on the target surface, which turns out to be a positioning error and a source of speckle noise on the laser vibrometer signal. A comparison between static measurement and numerical analysis has been performed, so that capabilities of the tracking technique were highlighted.

This paper presents the design and the characterization of a portable laser triangulation measurement system for measuring gap and flush in the car body assembly process. Targeting Human in the Loop (HILT) operations in the manufacturing sector, and in line with the vision of human empowerment with Industry 4.0 technologies, the instrument embeds features to ease operators’ activity and compensate possible misuse that could affect the robustness and the quality of data acquired. The device is based on a smartphone integrated with a miniaturized laser triangulation system installed in a cover. The device embodies additional sensors and control systems in order to guarantee operators’ safety (switching on and off the laser line based on specific conditions), support operators during the measurement execution task, and optimize the image acquisition process for minimizing the uncertainty associated to the measurement. The smartphone performs on-board processing and allows Wi-Fi communication with the plant IT infrastructure. Compliance to Industry 4.0 requirements is guaranteed using OPC-UA (Open Platform Communications—Unified Architecture) communication protocol enabling the exchange of live data with the plant middleware. The smartphone provides also an advanced high-resolution color display and well proven and ergonomic human–machine interfaces, which have been fully exploited in the design. The paper introduces the system optical layout and then presents the algorithms implemented to realize the gap and flush measurement. The paper finally presents the calibration of the instrument and estimates its calibration uncertainty in laboratory conditions. Then it discusses how performance decays when the operator handles the instrument on a reference car body. Finally, it shows the analysis of uncertainty when the device is used on real car bodies of different colors in a production line. It is observed that the measurement uncertainty of the whole measurement chain (measurand + instrument + operator + uncontrolled environmental conditions) is larger than the instrument calibration uncertainty because the measurement process is affected by the operator and the variable conditions of the production line.