Research On Key Technologies Of Wireless Network Large-scale Measurement System With A Light-pen

The light-pen vision coordinate measurement system has always been concerned for recent decades,for that the system could realize the hiding spots in-situ measurement,which can hardly be done by other portable measurement systems.The light-pen system's measurement accuracy and repeatability have been paid too much attention,however,its measurement range,by contrast,has been nearly ignored.In order to improve the measurement accuracy,repeatability and range of the light-pen system,this paper has concerned some technologies,such as the improvement of the light-pen structure,the feature point center positioning,the probe tip center positioning,the optimal design of the system structure and so on,on the basis of a deep analysis about related researches at home and abroad.The main work in this paper is as follows:1.Improve the the second-generation light-pen structure based on the direct linear transformation mathematical model.Several virtual light-pens,with different distances between the front plane where six control points lie and the back plane where other four ones lie,have been built skillfully by high accurate and repeatable movement of the coordinatge measuring machine's main axis.And the results of the virtual light-pen repeatability experiment and the accuracy contrast experiment show that this distance parameter has a large impact on the system's measurement repeatability along the optical axis and the whole system's measurement accuracy.2.It is thought that the ellipse center distortion error of feature points influence the accuracy of their center positioning,after the deep analysis of the reason why the accuracy is so poor.A new model based on the cross-ratio invariance is given to solve the feature points' ellipse center distortion error.And it is concluded that this error is what causes the unsatisfactory center positioning accuracy of the second-generation light-pen's feature points by the concentric circle test.3.The accuracy of the light-pen's probe tip center positioning has a direct influence on the whole system's measurement accuracy and repeatability.Based on invariable distances,a new self-calibration algorithm of the probe tip center positioning is given.And the result of the probe tip center self-calibration repeatability test,in different distances between the camera and the light-pen,shows that the given algorithm could meet the requirement of the system with sub-millmeter accuracy.4.Aim at the deficiencies of existing light-pen vision coordianate measuring machines,a new structure of the wireless network large-scale measurement system with a light-pen is presented.A smart camera,which can not only collect the light-pen's photos,but also process them,and a set of wireless network communication system are designed and verified by several tests.By the flexible Zig Bee wireless network,a computer,an adjustable light-pen and one or two smart cameras could make up a measurement unit.Furthermore,several measurement units can form a huge measurement network that could realize the in-situ measurement of large-scale objects with high accuracy.