Research On The Measurement Method Of Shield Tail Clearance Bansed On Line Structured Light

With the rapid development of China’s economy,the demand for underground rail transit construction is increasing.Shield tunneling is widely used in China’s underground rail transit construction because of its characteristics of fast construction speed,low labor intensity and high construction safety index.In the process of shield construction,the clearance between the inner wall of shield tail and the outer wall of segment is called the clearance of shield tail.The shield tail clearance is an important basis for segment selection.If the clearance exceeds the design range,the resistance of the shield machine will be increased and the driving speed will be reduced,or the shield tail will squeeze the segment,resulting in water leakage or surface settlement accidents.Therefore,in order to ensure the quality and safety of shield construction,it is necessary to measure the tail clearance in real time.At present,the measurement accuracy and stability of the existing measurement system cannot meet the requirements of on-site construction.Therefore,based on the above problems,this paper designed a shield tail clearance measurement system based on line structured light.The system has the characteristics of simple structure,high measurement accuracy and strong anti-interference ability,which can meet the requirements of shield construction and improve the automation degree and construction efficiency of shield construction.The main research contents of this paper are as follows:1.The widely used measurement methods of shield tail clearance and linear structured light at home and abroad are analyzed,and the shield construction technology is introduced.According to the characteristics of field shield construction,the requirement of shield tail clearance measurement is analyzed,and a method of shield tail clearance measurement based on line structured light is proposed.2.In-depth study of the key technology of measurement system calibration.In this paper,the imaging principle of camera and the calibration method of camera internal parameters are studied,and the internal parameters of camera are solved by checkerboard calibration method.The image processing method is used to process the optical strip image and obtain the optical strip information.According to the optical strip information combined with the optical plane calibration algorithm,the parameters of the light plane equation can be accurately calculated.3.Overall design of shield tail clearance measurement system according to construction characteristics.The selection of vision sensor and line laser is completed,and the vision measurement system and integrated control box structure is designed.The software design of the system is completed by referring to the technical parameters of the industrial computer,and an image recognition algorithm is designed according to the imaging characteristics of line laser on the end face of shield tail gap.4.The simulation model of shield tail clearance was constructed by using 3D modeling software to verify the feasibility and correctness of the measurement method.In order to verify the measurement accuracy of the system in practical applications,measurement repeatability experiments and absolute measurement experiments were carried out in the laboratory and at the shield construction site respectively.The experimental results show that the repeatability measurement accuracy of shield tail clearance is better than 0.3mm and the absolute measurement accuracy is better than 1.7mm,which meets the needs of on-site measurement.