Abstract: In the intelligent assembly in a narrow space,the datum surface pose needs to be measured.However,the existing attitude measurement devices have some shortcomings. For example,their sizes are large,or they require additional scanning motion mechanism. These disadvantages make devices difficult to deploy.The present study proposed a monocular active vision attitude measurement method based on two line lasers,which is suitable for the narrow space. First,the center points of the two line lasers were extracted for laser plane calibration. Second,according to the central projection relationship,the conversion matrix between the laser plane and the image plane was calculated. Then,the pixel coordinates of the line laser center point on the target plane were extracted and converted to camera coordinates.Finally,the RANSAC algorithm was applied to filter the anomalies and then the least square algorithm was used to fit the object plane equation to realize the attitude measurement of the spatial object plane.The experimental results show that the mean value of the roll angle measurement error is 0.029° and standard deviation is 0.016°. The mean value of the pitch angle measurement error is 0.035° and standard deviation is 0.025°. The validity of the method is verified by completing the plane attitude measurement in a cylindrical cavity with diameter of 170 mm and height of 520 mm using the method.

Key words: attitude measurement, vision measurement, line laser, monocular camera, confined space