Research On Key Technology Of Optical Target For Location Measurement Of Tunnel Boring Machine

In all kinds of complex underground shield construction environment,the guidance system with real-time pose measurement with full section in hard rock tunnel equipment(referred to as TBM)provides the most critical technical support for controlling the deviation between TBM excavation route and design axis.Therefore,in this paper,aiming at a new type of hybrid TBM,how to design an optical target with low complexity and high anti-noise capability to achieve accurate and efficient TBM pose measurement method,the research work is followed as:Firstly,this paper summarizes the current research status of the main TBM guidance system,analyzes its technical scheme and characteristics,and proposes a monocular vision pose measurement method for the pose measurement of a new hybrid TBM with the structural characteristics of two-stage propulsion system.According to the principle of projective invariance,the collinearity of each feature point in the topological structure is established,and its feature point sorting algorithm and feature point matching algorithm are given.Secondly,aiming at the problem of how to locate the center of laser spot quickly and accurately in optical target,the algorithm of equivalent intensity of laser spot center is proposed,and the accuracy of its center position and anti-interference ability are simulated and tested.The results show that the method is fast and effective,with high accuracy and strong anti-interference capability.Then,according to the principle of camera calibration,the camera calibration model is built.The ChArUco calibration is used to calibrate the camera internal parameters.On the basis of this,combined with the principle of weak perspective projection,the linear solution of PnP problem with multiple feature points is simplified.Aiming at the problem of poor precision and weak anti-noise capability of PnP linear solution,a nonlinear iterative optimization model based on reprojection error is proposed,which makes the approximate solution of linear equations further approximate the real pose with high precision and stability.Finally,the effectiveness of the algorithm is verified by using ArUco as the pose reference.The research results have important significance and reference value for the design of the actual hybrid TBM guidance system.For example,the six point plane laser optical target designed in this paper can also be widely used in related fields,such as robots,UAVs,aerospace and other high-end fields.