Research On Underwater Terrain Scanning System Based On The Linear Laser

The development and utilization of the ocean possess huge application prospect.Therefore,the effective means for underwater exploration is the prerequisite for marine development.At present,the exploration of underwater topography is dominated by sonar.However,the current sonar detection accuracy is very low,which cannot achieve high-precision scanning at close range.The way of applying laser scanning in water can solve these problems well.This paper presents scanning detection system based on linear laser.This system not only can realize underwater scanning and underwater positioning,but also can obtain the precise threedimensional reconstruction results after laser scanning.For the laser image processing algorithms,this paper proposed the center-line extraction algorithm based on multithresholding and extremum-based Gaussian fitting.Multi-threshold algorithm can effectively filter out background noise by using different thresholds.Gaussian fitting rule based on extremum method fits part of laser fringes with Gaussian function.The obtained results in the experiment have both the rapidity of threshold method and the high accuracy of Gaussian fitting.The main research work of this paper is as follows:First of all,based on the objective of the laser scanning research,the overall structure of the scanning system is designed.The research of underwater scanning based on the linear laser can be divided into two stages according to the different hardware platform of scanning system.Corresponding to these two hardware platforms,the design process of the laser scanning system under different software systems was completed.Secondly,center-line extraction of laser stripe is an indispensable part of underwater linear laser image processing research.This paper proposes the algorithm of center-line extraction of laser stripes combining multi-thresholding and extremum-based Gaussian fitting.The experiment verified that this method can compensate for the lack of accuracy and rapidity of the traditional laser stripe centerline extraction algorithm.Then,the calibration of the laser scanning system is a guarantee of the measurement accuracy of the laser scanning system.In this paper,a collinear quick calibration method is proposed.By comparing with other complex system structural parameter calibration methods.The final result of the experiment proved the feasibility of applying this calibration method to system calibration in underwater environment.Finally,in the linear laser underwater terrain scanning experiment,two different hardware platforms,including stepping motor sliding platform and underwater autonomous vehicle(AUV),were used for different underwater terrain conditions to achieve threedimensional underwater terrain.In the underwater target location experiment,for the underwater target model with known size,the laser scanning measurement result is compared with the original size,and the scanning accuracy of the system is analyzed.According to the experimental results,the linear laser scanning system designed in this paper can well achieve underwater terrain scanning and target positioning.