Long distance vision localization method based on triple laser beamstarget in coal mine

Long distance dynamic positioning of coal mine heading equipment has become the primary problem for an intelligent development of roadway. Accurate and reliable pose measurement and estimation is of great significance to improve heading efficiency. It is difficult to guarantee the stability and accuracy of the traditional measurement method because of the vibration and noise, magnetic and electrostatic interference in the coal mine environment. Compared with other positioning methods, visual measurement method has attracted much attention for its advantages of no contact and no cumulative error. In this paper, aiming at the problems of accuracy and stability of underground visual positioning, a long distance visual positioning method based on multiple laser beams is proposed in coal mine, and a three laser beams target is constructed by mining laser point instrument to solve the interference problems of low illumination, high dust and complex background. The boom type roadheader is taken as the application object, and the monocular vision measurement system of the roadheader body is constructed based on a triple laser beams target. The method of laser beam target image segmentation by color component and peak value clustering constrained is proposed. The Hessian matrix is used to solve the normal direction for each pixel points of the rough center line of the laser beam. The sub pixel feature extraction and location of the center line of the three laser beams are realized by Taylor expansion. A three point three line (3P3L) roadheader body pose estimation model is constructed, the least square loss function of the measurement model is established, the non iterative global optimal solution is estimated by minimizing the re projection error, and the optimal solution of the body pose of the roadheader is obtained. Furthermore, the error distribution of the main parameters of the measurement model is studied by numerical simulation. Finally, the roadheader body positioning system platform based on the triple laser beams target is built and evaluated experimentally. The results show that this method can meet the requirement of precise positioning in the harsh environment of coal mine.