Relative Pose Measurement Method Of The Subreflector Stewart Platform Based On Monocular Vision

In the field of astronomy,the Stewart Platform is used to adjust the pose of the Subreflector of the antenna in real time,so it is necessary to accurately measure the pose of the moving platform of the Stewart Platform.The measurement of the pose of the Stewart moving platform of is an urgent problem.Monocular vision only uses one camera to calculate the pose information of a single image,which has the advantages of no stereo matching,only need to calibrate internal parameters,large measurement range,simple structure,non-contact,etc.,and is very suitable for the pose measurement of parallel mechanism.This paper mainly studies a monocular vision measurement method based on non-coplanar cooperative target and EPNP algorithm,studies the image feature extraction,pose estimation algorithm and the design of the experimental system,and finally builds the system experimental platform to verify the pose measurement accuracy.In this paper,first of all,the working principle of monocular vision pose measurement is introduced,the camera imaging model is explained,and the coordinate relationship between the cooperative target and the camera is established.Then,various methods of image feature extraction are introduced,and the appropriate pose estimation algorithm is selected to solve the pose.For the collected images,we need to carry out image preprocessing first,and then select the appropriate center location method to extract the central coordinates of the image feature points,conduct simulation experiments to verify the extraction accuracy,and finally choose the square weighted center of mass method.Then,the position and pose of the extracted feature point coordinates are solved.The advantages of the EPNP algorithm and the process of solving the position and pose are introduced.Simulation experiments are carried out to verify the accuracy of the EPNP algorithm.Finally,in order to verify the accuracy of the measurement method proposed in this paper,an experimental platform of the Stewart platform for monocular vision pose measurement system was built.The experimental test showed that the measurement error of the system was kept within 0.1mm within the translation range of ± 30 mm of the parallel mechanism moving platform.In the ±5 ° rotation range,the measurement error is kept within 0.05 °.At the same time,the main source of measurement error is analyzed,which provides a method for improving the measurement accuracy of position and pose.The results show that the precision of the developed measurement system meets the precision requirements of the parallel adjustment mechanism of the antenna sub-surface,which verifies the reliability and effectiveness of the proposed method,and provides an effective means for realizing the closed-loop control of the parallel mechanism.