Online Measurement System For The Surface Inclination And Height Difference Of Metal Workpieces

The metal surfaces’ measurement is of significant importance in many industrialfields. The surface measuring system of metal pieces introduced in this paper can beapplied to detect whether the parameters fulfill the compliance requirements like theheight difference and inclination of machined metal surfaces’, in which metalsurfaces’ strong reflection characteristic and the real-time measuring requirement inindustry scenes have been taken into account of. Followings are the main researchcontents and key technologies of this measuring system:1. The linear structured light measurement mode is applied in this system. Thelight plane is projected perpendicularly to the measured pieces, which ensures themeasurement pattern of passive scanning. This system has gained the advantages ofsimple structure, not high cost and good reliability;2. Based on sensor calibration, the relationships between the three-dimensionalspatial coordinates and the ideal image coordinates are established directly. Thecalibration process is not flexible, and suitable for implementation of industrial fields;3. Research on center extraction methods of laser bars on highly reflectivemetal surfaces on the basis of real-time detection requirements, in which the grayscalegravity algorithm is applied to extract the pix coordinates. This method has moderateextraction accuracy;4. The stray point of metal pieces’ scan data was analyzed. The least squaresmethod is employed to fit the data and the Pauta criterion is utilized to remove thespurious points, which is on the basis of drawing up standard to judge and to removestray;5. By transforming the measured planes to the reference plane’s coordinate, theangle is easily calculated. The gradient is used to find the maximum tilt direction ofthe line, and the height difference could be calculated by the law of cosines. By usingmacro calculation, the influence of random error has been effectively reduced.The repeat accuracy of this system has been tested. The experimental resultsprove that the precision of inclination is0.046°RMS under the speed of4mm/sec, andthe precision of height-difference is0.072mm RMS, which meets the design expectations. Hence, this system can be applied to online industrial detection of highspeed and high precision.