Research Of Underwater Machine Vision For AUV Docking Control

Autonomous Underwater Vehicle(AUV) is an important research field which is integrated with many an oceanic high technology.The reclaim problem is one of the most demanding technologies of AUV that need to be researched and tackled.In this paper,the technologies of vision guidance of AUV docking are researched primarily.Firstly,the digital camera with high performance and advanced HALCON software are combined to overcome the difficulty of underwater machine vision and the complicity of image processing.To obtain the underwater space vision information properly and promptly,the programming language,images collecting, data format and camera triggering controlling are matched through soft and hard ware.The outer triggering synchronization of camera is designed to address the problem of asynchronism collecting which is caused by exposure asynchronism of double-camera when AUV is moving,which can be used to operate outer triggering experiment.The figuring array consisted by luminous diode is designed to deal with the problems of illumination power and light-house radiation,which solved target displaying for AUV docking.Secondly,the method of underwater stereo calibration based on projection homography is designed to resolve error precision of vision position in the process of docking,improve the measurement precision during the process of target position.The method utilize linear model to calculate the optimization of the parameters of camera,and figure the non-linear precision by considering the target function of lens aberration,together with the result of internal and external parameters,which is highly precision,lower cost,simply operated and adapted to underwater local calibration.The algorithm of noising point eliminating based on region marked is proposed by adopting calibration board images through optimized algorithm of threshold segmentation,to settle the problem of feature circle segmentation and abstraction,which can also eliminate the disturb of underwater noise and abstract all feature circles.To verify the veracity of calibration result,the 3-D measuring experiment of underwater target is carried out,the absolute error of the precision degree is±5mm level.Thirdly,due to the problems of noise and detailed fuzzy for underwater images,gauss smoothly filter is developed.The object edge point is eliminated through morphologic filter,and the contrast of underwater images is enhanced and the detail of images is distinguished more easily by using prey linear transform method.The algorithm of Canny sub-pixel edge detecting is introduced to do with the problem of contour abstraction for underwater target,and use the improved snake module to abstract the graphics contour from all the objects precisely.Fourthly,a few circle targets which is different in internal shape is proposed to install on the bottom of the docking cabin to overcome the target recognizing problem during underwater docking process,all circle targets are searched through shape template matching method.Because of model searching problem, the searching tactic is put forward based on regular model,and through adjusting and optimizing parameters,the searching rate and accuracy is improved. According to the target position demanding of the underwater docking platform, the relative coordinate between all the target points and camera is figured out precisely,through calculating the intersection points coordinate of each target and lens and combing the internal and external parameters after calibrating.To validate the practicality of vision position algorithm,the night experiment is made out,and simulates the correct target position for AUV in the underwater environment successfully.Lastly,according to the nonlinear and uncertainty during AUV movement,the H_∞controller is developed for AUV reclaiming,which is based on 6 DOFs of AUV mathematics modeling.To verify the effectiveness of vision guidance algorithm,according to the designed proportion and combing 11 freedom degree of the test shelf,the AUV docking simulating platform is set up,and vision algorithm and docking controlling programming are designed and developed. During the experiment,the docking process is divided into 4 freedom degree approaching phase,suspending position phase and entrance cabin phase.The docking test in the night environment is processed successfully,which can make a good basis for the pool experiment for the AUV docking.In order to achieve autonomous reclaiming technology for AUV,vision guidance method is researched,accomplish camera stereo calibration,and the poison precision degree is mm level.In the process of stereo vision matching,the searching tactic is put forward based on regular model,and calculate the position through vision difference.The effectiveness and practicality of the presented methods are verified through deflating scaling experiment.The research and conclusion of the thesis have a great both theoretical and practical value for the AUV,such as safety,reliability,remotely sailing and landform reconnaissance.