Measurement model and calibration method of involute profile of spur gear

The application of structured light vision measurement technology can realize the three-dimensional non-contact on-line measurement of industrial parts. The calibration method of structured light vision model is studied. Through calibration, the camera internal parameters, distortion coefficient and structured light plane equation can be obtained. However, in the actual measurement, a new dimension measurement model and target dimension calculation method should be established according to the measurement object (i.e. the involute profile of spur gear). According to the geometric characteristics of involute tooth profile and structured light vision model, the following problems are to be solved through the establishment of measurement model in this chapter:

1). The pseudo light plane perpendicular to the rotation axis of spur gear is established, and the three-dimensional points reconstructed through the structured light vision model are projected onto the pseudo light plane to correct the influence on the tooth profile measurement caused by the non perpendicularity between the structured light plane and the rotation axis of spur gear.

2). The measured three-dimensional coordinates are converted to the two-dimensional coordinate system established on the structured light plane, and the calculation of the radius of the base circle and the tooth profile error are completed through the two-dimensional coordinates of the feature points on the involute in the plane.

Based on the geometric characteristics of spur gears, a structured light vision measurement model of involute tooth profile error is established in this paper. Firstly, considering that the straight line structured light plane is not perpendicular to the rotation axis of spur gear, the pseudo structured light plane perpendicular to the rotation axis is established, and the calibration method of pseudo structured light plane is given; Secondly, the target point reconstructed by the structured light vision system is projected to the pseudo structured light plane, and the local coordinate system is established on the light plane to convert the three-dimensional coordinates of the projection point into two-dimensional coordinates; Finally, the calculation method of involute tooth profile base circle radius and tooth profile error is deduced by coordinate method.

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