         In-situ measurement is applied to obtain the overall geometric profile information of the blank. The measurement result is usually used to establish the workpiece coordinate system and carry out the compensation of machining path planning. Especially for large-scale curved thin-walled parts such as aircraft skin, there is a huge deviation between the workpiece and the theoretical model. So, the in-situ measurement before machining has become an important step of processing technology. However, the motion accuracy of machine tool is much lower than that of off-line measurement platform. Therefore, it is necessary to compensate the measurement results of the in-situ measurement system for accurate results.

        The line laser sensor is a non-contact active measuring sensor. It can obtain the three-dimensional information of an object by directly emitting a beam of light to the object surface. It has the advantages of high measuring efficiency, wide measuring range, no measuring force, no sensor damage, no probe radius compensation and so on. The sensor has been widely used in off-line measurement in the industry. Due to the feature of line laser measurement, working environment and other factors, the in-situ laser measurement accuracy is still lack of guarantee. And the compensation of in-situ line laser measurement system is also lack of research. Blanco.D analyzed the influence of external environment light on the repeatability of the measured data. Van.G.N proposed a method to evaluate the measurement accuracy of the line laser sensor. Aguilar.J. J studied the influence of the measured parts’ shape and material on the measurement results through simulation and experiment. Vukasinovic.N studied the influence of the measuring angle of the line laser on the measurement results. The above conclusions are qualitative. For the application of in-situ measurement, a quantifiable mathematical model is needed.

        In this paper, the influence of the line laser measuring angle factors is researched. The physical model of the laser light path is deduced based on the laser triangulation principle. Then the measuring angle compensation model can be expressed quantitatively. At the same time, the algorithm to obtain the measuring angle based on the free-form surface measurement results is studied. It’s an important parameter of compensation model. Through an actual experiment, the measuring angle compensation model is used to modify the measurement results. Experimental results show that the compensation results are closer to the real value, which verifies the effectiveness of the measuring angle compensation model. By experiment, we also explored the influence law of the working environment factors on measurement accuracy, such as the workpiece material, the curvature of the area to be measured, and the exposure rate. The influence degree of the above factors on the measurement accuracy is quantified, which provides an experience reference for parameter setting before the actual measurement.


Research on In-Situ Measurement Technology of NC Machining Based on Line Laser Sensor

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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