Laser mark automatic tracking extensometer control method based on uncalibrated visual servo

Abstract

The invention discloses a laser mark automatic tracking extensometer control method based on uncalibrated visual servo. An image Jacobian matrix on-line identification method is adopted, the mapping relation between the actual distance between a laser mark and a sample mark, namely, the tracking displacement of the laser mark and image space tracking displacement is built, a controlled quantity is calculated by identifying the pixel distance difference between a Jacobian matrix and the central points of the two marks through a Karman filter, a servo motor is controlled to drive a pentaprism to rotate, the automatic tracking of the laser mark on the sample mark is achieved, and the laser mark displacement in the extending process is a sample deformation quantity. The method not only avoids the camera calibration step of an existing video extensometer and measuring errors introduced from the step, but also achieves the precise whole-process tracking of the laser mark on the sample mark, and is strong in environmental disturbance resistance capacity and high in tracking precision.

Description

technical field [0001] The invention relates to an automatic tracking control method, in particular to a laser marking automatic tracking extensometer control method based on non-calibration visual servo. Background technique [0002] Material deformation measurement is the basis for characterizing material properties. Video extensometer has become the main tool for material deformation measurement because of its non-contact measurement method, which is almost suitable for most material deformation measurement and has high measurement accuracy. At present, the video extensometer generally prints marks on the upper and lower ports of the test sample, tracks the displacement of the upper and lower marks in real time during the stretching process, and then obtains the difference between the two displacements according to the digital image processing method as the image. The material deformation amount in space is finally converted into the actual deformation amount of the mate...

AI Technical Summary

Problems solved by technology

However, these methods need to design camera calibration templates and calibration algorithms, and the camera position, focal length and other parameters will change in repeated experiments, so re-calibration is required, which makes the measurement process cumbersome and introduces errors

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